COD
Contact Dermatitis • Original Article
Contact Dermatitis
Cost-of-illness of patients with contact dermatitis in Denmark Bjørn Sætterstrøm1 , Jens Olsen1 and Jeanne Duus Johansen2 1 Centre for Applied Health Services Research and Technology Assessment, University of Southern Denmark, 5000 Odense C, Denmark and 2 Department of
Dermato-Allergology, National Allergy Research Centre, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
doi:10.1111/cod.12231
Summary
Background. Contact dermatitis is a frequent occupational and non-occupational skin disease. Objectives. To investigate the effects of contact dermatitis on labour market affiliation and societal costs in terms of healthcare costs and production loss. Methods. A total of 21 441 patients patch tested either in hospital departments or at dermatological clinics in the period 2004–2009 were included in the study. The analyses were stratified by children (age 0–15 years), occupational contact dermatitis (age 16–65 years), and non-occupational dermatitis (age ≥ 16 years). Controls were selected from a 30% random sample of the population. Individual encrypted data were retrieved on healthcare utilization, socio-demographics, education, labour market affiliation and transfer payments from public registers in Denmark for cases and controls. Results. Attributable healthcare costs for 4 years prior to patch testing (1 year for children) and the year after patch testing were ¤959 for children, ¤724 for occupational contact dermatitis, and ¤1794 for non-occupational dermatitis. Productivity costs for the same period were ¤10 722 for occupational contact dermatitis and ¤3074 for non-occupational contact dermatitis. Conclusions. The main findings of this study were that there were statistically significant attributable healthcare costs for both children and adults, and statistically significant productivity loss for adults. Key words: atopic dermatitis; contact dermatitis; dermatitis; eczema; healthcare costs; labour market affiliation; occupational contact dermatitis; productivity costs.
Introduction Contact dermatitis is a frequent occupational and nonoccupational skin disease, with an estimated 25 000 new cases being recognized by dermatologists each year in Denmark (1). This corresponds to an incidence of 4.5 per 1000 inhabitants, and gives prevalence estimates of 7.3–12.9% for the best and worst case scenarios (1).
Correspondence: Jeanne Duus Johansen, Department of DermatoAllergology, National Allergy Research Centre, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark. Tel: +45 39777301; Fax: +45 39777118. E-mail: [email protected] Accepted for publication 1 February 2014
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In other European countries, contact dermatitis is also a frequent disease (2), and constitutes up to 30% of all recognized occupational diseases (3). Disease severity and long-term prognosis vary, but the latter is generally regarded as poor. Most studies concern hand eczema, and have shown a considerable need for medical attention and negative psychosocial consequences resulting from hand eczema (4). Long-term sick leave and an impaired ability to work affect at least 5% of those with hand eczema (4) and up to 23% of workers in high-risk occupations such as hairdressing (5). In spite of the frequency of contact dermatitis and the potential severe consequences, only a few systematic studies exist regarding the direct economic burden of this disease.
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COI OF CONTACT DERMATITIS • SÆTTERSTRØM ET AL.
The objective of this study was to investigate the effects of contact dermatitis on labour market affiliation and societal costs in terms of healthcare costs and production loss. We performed separate analyses for occupational contact dermatitis (OCD) and non-OCD in adults and in children. We used an incidence approach, enabling us to identify the effects in the first year after diagnosis, and we applied register-based analyses to patients identified in a clinical database.
Materials and methods Cases and controls
Cases were identified as individuals with contact dermatitis in the period 2004–2009. The cases had been seen and patch tested either in a hospital dermatology department or at a dermatological clinic in the primary care sector. Anyone who was patch tested was included, and the analyses were stratified by three categories: children (age 0–15 years), OCD (age 16–65 years), and non-OCD (age ≥ 16 years). Cases with OCD were identified by use of the MOAHLFA index, assigned by a dermatologist at the time of investigation. All cases in which work is a causal or contributory factor is defined as occupational in Denmark, and reported to the Board of Occupational Health. Severity or occupational consequences are not part of the criteria, which means that cases in which all symptoms have cleared will also be included. Matching
According to Caliendo and Kopeinig (6), variables used in the matching should be unaffected by participation. Hence, variables should either be fixed over time or measured before participation, which, in this study, would correspond to the onset of disease. However, owing to patient delay [from onset to the patient visiting a general practitioner (GP)] and medical delay (from the visit to the GP to a visit to a dermatologist), it was not possible to establish the exact onset of disease. Therefore, ensuring that the variables used for matching were unaffected by participation was not feasible. Hence, the quality of the matching was problematic. Various studies have been conducted on the length of delays. Skoet et al. (7) reported a median delay of 2 years (average of > 4 years) for occupational hand eczema from onset until notification to the Board of Occupational Health. For hand eczema in general, the median delay from onset until the patient was seen by a dermatologist was 6 months (3 months of patient delay and 3 months of medical delay), as reported by Hald et al. (8). As a compromise, we chose to match at 1 year prior to testing.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Contact Dermatitis, 71, 154–161
Table 1. Variables used for matching
Children (0–15 years) Age Sex Geographical origin Cohabitation status Socioeconomic status Education High-risk occupationa Household with childrenb
X X X – – – – –
Non-occupational Occupational contact contact dermatitis dermatitis X X X X X X – –
X X X X X X X X
a Employment in an occupation with a high incidence (hairdressers, dental surgery assistants, bakers, kitchen workers, cooks, and butchers) (8) within 4 years prior to patch testing. b Membership of a household with children.
Table 1 shows the variables that we used for matching. They were primarily basic socio-demographic variables. However, for adults with occupational contact dermatitis, dummies for being in an occupation with a high incidence of contact dermatitis and for being in a household with children were also included, from the perspective that these variables were also strong predictors of contact dermatitis. Controls were selected from a 30% random sample of the population by the use of propensity score matching (6), in which the five nearest neighbours are selected for each case on the basis of the likelihood of disease being present. Controls with a visit to a dermatologist and more than one prescription of steroid lotion [Anatomical Therapeutic Chemical Classification System (ATC) codes beginning with D07] were excluded. Cases and individuals who migrated or died during follow-up were also excluded from the control group before matching. Study design
This study was designed as a register-based cost-of-illness study. The difference between costs for cases and controls was regarded as being attributable to the disease. As the exact onset of disease was not determinable, it was not possible to be certain whether costs were entirely attributable to the disease until after the patient had been tested. Therefore, an approach was chosen whereby yearly ‘attributable’ costs were estimated from 4 years prior to patch testing until 1 year after patch testing, although, for children, it was only 1 year before and 1 year after patch testing, because children included newborns. It was assumed that this period would cover the majority of attributable costs incurred, and that, as the date of patch testing was approached, the frequency of disease in the case group would increase, hence increasing the rate
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of costs attributable to the disease. Healthcare costs and productivity loss for cases and controls were determined for each year and compared. Estimation of costs
Healthcare costs included utilization of primary and secondary healthcare services and prescription medicine. Healthcare costs in the primary healthcare sector were defined as the fees paid from the public health insurance to healthcare professionals for visits and other services. With respect to the secondary healthcare services, the Danish diagnosis-related group (DRG) tariffs, defined as the average cost per admission, were used as the unit cost estimates for admissions. The Danish ambulatory grouping system (DAGS) tariffs, defining the average cost per visit, were used as the unit cost estimates for outpatient or emergency room visits in the secondary healthcare sector. To determine the cost of prescription medicine, the market price was used, including both reimbursement and co-payment parts. Healthcare provision (primary and secondary care) in Denmark is, to a great extent, publicly funded, as 85% of healthcare costs are financed through taxes. Healthcare is mainly provided by the regional authorities. The patients make co-payments for prescription drugs, dentist services, and visits to physiotherapists, chiropractors, etc. The Danish DRG and DAGS charges are used for activity-based funding in the hospital sector. The charges are estimated by the national health authorities on the basis of costing data from Danish hospitals, and the Danish DRG system was initially inspired by the DRG systems developed in the United States. For individuals in the labour market force (aged 18–65 years and excluding individuals who have taken early retirement, retired individuals, and pensioners), productivity costs included long-term sick leave, that is, > 24 days, for both adult cohorts, and the cost of vocational rehabilitation for adults with OCD. An assumption was made that the entire period of benefits (sickness or rehabilitation) represented 100% lost productivity. According to the human capital method, productivity losses were valued at the average earnings of ¤37.4 per hour worked (available from Statistics Denmark). The types of employment with reduced productivity are characterized by varying durations and frequencies. Hence, the burden to society in terms of productivity loss may best be analysed by adding together the weeks of benefits in each category.
database contains information about individuals tested on suspicion of contact dermatitis at one of 12 different clinics (three of which were in hospitals) spread over the entire country. There was one record for each test visit, and each record contained information about the test date, age, sex, and outcome of patch tests performed at the allergy clinics, as well as whether the disease was caused by the occupation. We excluded individuals with multiple test visits. There were 43 733 observations in the database, with the first test being recorded in 1985, and the database is still active. The individual civil registration number in Denmark allows for the connection of information between different registers. The advantages of such register connections have been well illustrated in Davidsen et al. (10). For this study, we used individual encrypted data on healthcare utilization, socio-demographics, education, labour market affiliation, transfer payments, migration and death for the cases identified in the clinical database and for a 30% random selection of the Danish population. These data were supplied and hosted by Statistics Denmark. To describe healthcare utilization, we used data from the Danish National Health Service Register, the Danish National Patient Register, and the Danish National Prescription Registry. These registers hold detailed information about the use of healthcare resources. Danish legislation permits researchers and others to access these registers. To describe labour market affiliation, we used data from the Occupational Classification Module (AKM), which is a model that generates information on the basis of various registers. The information for the analysis of productivity loss was retrieved from the National Labour Market Authority’s longitudinal database DREAM, which holds information on transfer payments for all Danish citizens on a weekly basis. The currency was translated into euros according to a 7.50 DKK/euro exchange rate. Costs were discounted at a 3% discount rate and adjusted to similar price levels (fixed at 2010 price levels). Statistical analysis
Analyses were performed with the statistical package sas 9.2 for Windows (SAS Institute, Cary, NC, USA). The Wilcoxon test was used for comparison of the costs between cases and controls. For any test, a significance level of 5% was chosen (α = 0.05).
Data
Results
Cases were identified in a clinical database run by the National Allergy Research Centre (9). This
Forty-three thousand seven hundred and thirty-three observations were made for 40 201 unique individuals in
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Table 2. Demographics of cases 2004–2009
Children Occupational contact dermatitis Non-occupational contact dermatitis Total
n
Female (%)
Age (years)
1228 2191 18 022 21 441
63 61 66 –
11.6 38.3 46.8 –
the clinical database. Thirty-seven thousand one hundred and ninety-one individuals had only one observation, and of these, 22 376 individuals were incident in the period 2004–2009. Nine hundred and thirty-five individuals had missing information on matching variables. Thus, the final sample for analysis was 21 441, and the majority of these were adults with non-occupational dermatitis. Table 2 shows the sample that was eligible for analysis. The majority of cases were women, and the average age at patch testing and diagnosis in children was 12 years. For adults, the diagnosis was made at 38 years of age in persons with OCD, and at 47 years of age in patients with non-OCD.
For children, however, the attributable healthcare cost decreased from ¤556 at 1 year before recognition to ¤403 at 1 year after, totalling ¤959 for the 2 years. The reduction was especially driven by reductions in inpatient admissions and primary care. Healthcare costs attributable to OCD remained constant for the first 3 years of the study period. However, increases in the year before recognition (primary care and outpatient visits) and the year after (outpatient visits and inpatient admissions) drove up the total attributable healthcare cost from ¤58 in year 2 before recognition to ¤390 in the year after recognition. The total attributable healthcare cost per case of OCD over the entire period was ¤724. For adults with non-OCD, the attributable healthcare cost increased throughout the study period, from ¤215 at 4 years before recognition to ¤561 at 1 year after. The total attributable healthcare cost per case of non-OCD over the entire period was ¤1794. The increase was driven by increases in the secondary care sector escalating towards the end of the study period.
Productivity loss Healthcare costs
Figure 1 and Table 3 shows attributable healthcare costs for the three populations analysed from the 4 years before patch testing (1–4) until the year after patch testing (5). Wilcoxon tests showed that healthcare costs for cases were significantly higher (α = 0.05) than those for their matched controls, with the exception of OCD dermatitis inpatient admissions in years 1, 4, and 5. There was a tendency for attributable healthcare costs to increase, especially as the end of the period was approached.
Figure 2 shows the labour market effects of OCD in terms of weeks with long-term sickness benefits and labour market rehabilitation benefits. The figures are averages for the entire population. The trend for productivity loss was similar to that for healthcare costs: the productivity loss increased towards the end of the study period. Labour market rehabilitation benefits were constant at 0.2 weeks per year until disease recognition, and subsequently increased to 0.8 weeks per year. Long-term sickness benefits increased throughout the period, from 0.5 weeks in year 1 to 3.0 weeks in
Fig. 1. Attributable total healthcare costs per case per period [before (1–4) and after (5) recognition] (2010 euros). OCD, occupational contact dermatitis.
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Table 3. Total healthcare costs per person per period [before (1–4) and after (5) recognition] (2010 euros)
Children
Case
OCD
Control Attributable Case
Non-OCD
Control Attributable Case
Control Attributable
Drugs Primary care Outpatient Inpatient Total Total Total Drugs Primary care Outpatient Inpatient Total Total Total Drugs Primary care Outpatient Inpatient Total Total Total
Years 1
2
3
4
5
– – – – – – – 127 145 181 357 811 765 46 215 188 227 636 1265 1051 215
– – – – – – – 115 146 227 419 906 831 75 227 197 257 688 1369 1137 232
– – – – – – – 114 162 225 416 917 859 58 240 207 312 775 1535 1236 299
92 185 216 425 917 361 556 138 229 331 340 1037 882 155 268 291 431 857 1847 1360 487
79 119 296 282 777 375 403 141 185 658 463 1447 1057 390 265 232 597 1015 2110 1549 561
OCD, occupational contact dermatitis. Results in bold were statistically significant as compared with controls (Wilcoxon, α = 0.05).
Fig. 2. Weeks of benefits attributable to contact dermatitis per case per period [before (1–4) and after (5) recognition] (2010 euros). OCD, occupational contact dermatitis.
year 5. The largest absolute increases occurred in the years before and after recognition. The value of the productivity loss was ¤8498 attributable to sickness and ¤2224 attributable to vocational rehabilitation for the entire period. Non-OCD patients had a much lower attributable productivity loss than OCD patients (data not shown). Thus, long-term sickness benefits increased from 0.3 weeks per year to 0.8 weeks in year 5. The value of the productivity loss for non-OCD patients was ¤3074 attributable to sickness for the entire period.
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Discussion Only a few previous studies have been published on the healthcare costs and productivity loss per case of OCD. In most studies, the costs were based on estimates, but, by the use of nationwide registers, we were able to obtain a high level of detail. For every incident case of OCD or non-OCD for adults and children, the healthcare costs attributable to the disease for the 4 years prior to registration for adults and 1 year for children in the database at the time of patch
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testing and the year after registration were ¤959 for children, ¤724 for OCD, and ¤1794 for non-OCD. In terms of productivity loss, the costs for the same period were ¤10 722 for OCD and ¤3074 for non-OCD. The decrease in children’s attributable healthcare costs after patch testing was consistent with intuition. The diagnosis of contact allergy in children may be challenging, as the clinical picture may be confused with atopic dermatitis for a while, or contact allergy may be a complication in atopic dermatitis, which is hard to recognize in a situation of chronic fluctuating skin disease (11). Therefore, healthcare costs may be high until recognition; however, once the correct diagnosis has been made, the healthcare demand reduces, resulting in less expensive treatment, indicating a clear benefit of patch testing and the subsequent intervention. The healthcare costs for patients diagnosed with OCD were increased as compared with controls in the whole observation period, although only modestly until 1 year prior to patch testing (Fig. 1). It seems that patients may suffer from minor symptoms for some years, and that, when disease worsens, referral to dermatologists is made and patch testing is performed. This fits with data showing that the mean duration of disease was 4 years at the time when it was recognized as occupational by the Danish Board of Industrial Injuries (3). The medical costs continued to rise after patch testing, as the causes and prevention of occupational skin disease are complex, and preventive measure need to be implemented at the workplace, which may take time, meaning that causative exposures cannot always be avoided. In a recent study on occupational hand eczema in Germany, the annual healthcare cost for managing work-related chronic hand eczema was ¤3309 annually (12). This is much more than we found in our study. The populations under study differed, as our study population included all patch tested cases, including those with no current symptoms or minor symptoms, whereas Diepgen et al. based their calculation on patients with refractory work-related hand eczema (12). Long-term sickness and rehabilitation increased just before and after patch testing, and the total cost per person was ¤10 722 for the 5 years of observation. In 2011, 2660 cases of OCD were reported to the Danish Board of Industrial Injuries (13); this would translate into a total cost of productivity loss of ¤28.5 million. In Germany, the productivity losses attributable to OCD are estimated to be more than ¤1.5 billion a year (14), and in the EU they are estimated to be more than ¤5 billion a year (15). These estimates depend on the actual costs in different countries and the quality of the data used for calculations.
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In our study, productivity losses were valued according to the average earnings of ¤37.4 per hour worked available from Statistics Denmark, which corresponds to ¤280.5 for a working day of 7.5 hr, whereas in Germany the cost of one lost working day used for calculations was estimated to range from ¤400 to ¤700 (14). In our study, we only included long-term sickness defined as > 24 days in a row per year, as information about shorter sick leave is not available from the Danish registers. This is likely to have resulted in an underestimation of the costs. In a recent study on patients with occupational hand eczema who entered a rehabilitation programme, 62.9% reported taking sick leave in the previous year, with a mean of 76.4 days (16). In a Swedish 12-year follow-up study on occupational skin disease, 48% of the cohort had taken sick leave of at least 7 days in duration (4), whereas in Germany the average length of sick leave for occupational skin disease was estimated to be 14 days (14). Non-OCD in adults showed larger medical costs than those for OCD for the whole study period, and an increase in costs in year 3 (prior to patch testing), in contrast to OCD, for which the increase mostly occurred after patch testing. The main driver of the increase in attributable costs of non-OCD was secondary care, and the draw on the secondary health sector was made sooner in the observation period than for OCD. This may mean that those with (suspected) OCD are patch tested sooner after referral to the secondary healthcare sector than those with non-OCD, in line with the guidelines on diagnosis of OCD (17), whereas, in non-occupational cases, this may be more up to the individual judgement of the doctor. As we do not know the time of onset, it is not possible to say whether there is more delay in the treatment of one group than in the treeatment of the other. Also, for non-OCD, the loss of productivity costs exceeded the medical costs, so even though the disease was not primarily occupational, functional or social impairments could result in the need for labour market rehabilitation. The total cost per case of non-OCD was ¤3635 over a 5-year period. Non-OCD is much more frequent than OCD, and thus the total cost (¤80 million) was larger than the collective cost for OCD. In a German study of 310 patients with chronic hand eczema, the yearly heathcare cost was approximately two to three times higher for those with occupational hand eczema than for those with non-occupational hand eczema. The costs attributable to productivity loss were also larger in the group with occupational hand eczema (12). This study compared patients with a similar clinical picture, that is, hand eczema, whereas our study population was
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much more heterogeneous, as the inclusion criterion was patch testing, and there were no requirements concerning the clinical presentation. In 2008, the direct cost of contact dermatitis in the EU was estimated to ¤2.3 billion per year (18); if it is assumed that the incidence and cost of non-OCD could be extended from our study to the rest of the EU, the total cost would be ¤6.4 billion. In this study, we calculated the direct costs of illness caused by contact dermatitis in children and adults, and in occupational and non-occupational cases. A matched control group was included, and the difference between the costs for cases and controls was regarded as being attributable to the disease. However, identifying the onset of disease was problematic. We knew the date when patients were seen at a dermatologist for contact dermatitis; however, this has been shown to be delayed to varying extents. Therefore, a compromise was made, and 1 year before patch testing was selected for matching. Matching at any year before patch testing would risk the inclusion of both healthy people and patients with disease in the case group. Some of the rehabilitation is likely to be productive. Therefore, the assumption that the entire period of benefits (sickness or rehabilitation) was lost entirely may lead to an estimate that is too high in the case of vocational rehabilitation. Propensity score matching is used to eliminate baseline differences, in order for differences between a set of populations to be attributed entirely to the disease. The problem with using propensity score matching when the exact onset of disease is not known is that the elimination of baseline differences may be jeopardized. This is the problem with using real-life data rather than performing isolated experiments. If the onset of disease is not known, there is a risk that the information used for matching will have already been affected by the disease. If this is the case, there is a risk that we have not selected a matching set of individuals. Thus, we will not be able to attribute the difference between the groups to the disease. In the present study, there may only be a problem in the case of OCD, in which three variables used for matching (socio-economic status, education, and highrisk occupation) may have been affected if onset did occur prior to matching.
This study covered only the 4 years prior to recognition and 1 year after recognition. Studies have shown that the prognosis of OCD is poor (19–21). Therefore, positive attributable costs may be incurred long after the recognition. Furthermore, we were not able to include OTC drugs and other non-recorded costs. Another important drawback was the lack of information on sick leave for < 24 days in a row in a year. Because of these issues, the estimates given in this study may be considered to be conservative. In estimating the total cost of contact dermatitis, it should be kept in mind that only an estimated 25% of those reporting symptoms of contact dermatitis were patch tested (1) and included in this study.
Conclusions The main findings of this study were that there were statistically significant attributable healthcare costs for both children and adults, and statistically significant productivity losses for adults, in persons with contact dermatitis in comparison to the matched controls. The most important problem that this study faced was identification of the onset of dermatitis, as there may be a long delay from onset until medical attention. This made the determination of the appropriate study period and the quality of the matching problematic.
Acknowledgements This study was performed in collaboration with the National Allergy Research Centre and the Centre for Applied Health Services Research (CAST). The members of the Danish Contact Dermatitis Group and doctors contributing to the data collection are gratefully acknowledged: Niels Kren Veien, Hans Lomholt, Henrik Sølvsten, and Anne Funding (Aalborg); Mette Sommerlund (Aarhus); Niels Henrik Nielsen (Bagsværd); Anne Danielsen, Mads Nielsen, and Rune Lindskov (Copenhagen); Torkil Menn´e (Gentofte); Aksel Otkjær, Knud Kaaber, and Morten Østerballe (Herning); Susanne Vissing (Hørsholm); Berit Kristensen and Ove Kristensen (Kalundborg); Klaus Ejner Andersen and Evy Paulsen (Odense), Christian Avnstorp, Anne Hjorther, and Bent Staberg (Rødovre); Bo Lastein Andersen (Svendborg); and Jens Thormann and Henrik Thormann (Vejle).
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Contact Dermatitis • Original Article
Contact Dermatitis
Cost-of-illness of patients with contact dermatitis in Denmark Bjørn Sætterstrøm1 , Jens Olsen1 and Jeanne Duus Johansen2 1 Centre for Applied Health Services Research and Technology Assessment, University of Southern Denmark, 5000 Odense C, Denmark and 2 Department of
Dermato-Allergology, National Allergy Research Centre, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
doi:10.1111/cod.12231
Summary
Background. Contact dermatitis is a frequent occupational and non-occupational skin disease. Objectives. To investigate the effects of contact dermatitis on labour market affiliation and societal costs in terms of healthcare costs and production loss. Methods. A total of 21 441 patients patch tested either in hospital departments or at dermatological clinics in the period 2004–2009 were included in the study. The analyses were stratified by children (age 0–15 years), occupational contact dermatitis (age 16–65 years), and non-occupational dermatitis (age ≥ 16 years). Controls were selected from a 30% random sample of the population. Individual encrypted data were retrieved on healthcare utilization, socio-demographics, education, labour market affiliation and transfer payments from public registers in Denmark for cases and controls. Results. Attributable healthcare costs for 4 years prior to patch testing (1 year for children) and the year after patch testing were ¤959 for children, ¤724 for occupational contact dermatitis, and ¤1794 for non-occupational dermatitis. Productivity costs for the same period were ¤10 722 for occupational contact dermatitis and ¤3074 for non-occupational contact dermatitis. Conclusions. The main findings of this study were that there were statistically significant attributable healthcare costs for both children and adults, and statistically significant productivity loss for adults. Key words: atopic dermatitis; contact dermatitis; dermatitis; eczema; healthcare costs; labour market affiliation; occupational contact dermatitis; productivity costs.
Introduction Contact dermatitis is a frequent occupational and nonoccupational skin disease, with an estimated 25 000 new cases being recognized by dermatologists each year in Denmark (1). This corresponds to an incidence of 4.5 per 1000 inhabitants, and gives prevalence estimates of 7.3–12.9% for the best and worst case scenarios (1).
Correspondence: Jeanne Duus Johansen, Department of DermatoAllergology, National Allergy Research Centre, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark. Tel: +45 39777301; Fax: +45 39777118. E-mail: [email protected] Accepted for publication 1 February 2014
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In other European countries, contact dermatitis is also a frequent disease (2), and constitutes up to 30% of all recognized occupational diseases (3). Disease severity and long-term prognosis vary, but the latter is generally regarded as poor. Most studies concern hand eczema, and have shown a considerable need for medical attention and negative psychosocial consequences resulting from hand eczema (4). Long-term sick leave and an impaired ability to work affect at least 5% of those with hand eczema (4) and up to 23% of workers in high-risk occupations such as hairdressing (5). In spite of the frequency of contact dermatitis and the potential severe consequences, only a few systematic studies exist regarding the direct economic burden of this disease.
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The objective of this study was to investigate the effects of contact dermatitis on labour market affiliation and societal costs in terms of healthcare costs and production loss. We performed separate analyses for occupational contact dermatitis (OCD) and non-OCD in adults and in children. We used an incidence approach, enabling us to identify the effects in the first year after diagnosis, and we applied register-based analyses to patients identified in a clinical database.
Materials and methods Cases and controls
Cases were identified as individuals with contact dermatitis in the period 2004–2009. The cases had been seen and patch tested either in a hospital dermatology department or at a dermatological clinic in the primary care sector. Anyone who was patch tested was included, and the analyses were stratified by three categories: children (age 0–15 years), OCD (age 16–65 years), and non-OCD (age ≥ 16 years). Cases with OCD were identified by use of the MOAHLFA index, assigned by a dermatologist at the time of investigation. All cases in which work is a causal or contributory factor is defined as occupational in Denmark, and reported to the Board of Occupational Health. Severity or occupational consequences are not part of the criteria, which means that cases in which all symptoms have cleared will also be included. Matching
According to Caliendo and Kopeinig (6), variables used in the matching should be unaffected by participation. Hence, variables should either be fixed over time or measured before participation, which, in this study, would correspond to the onset of disease. However, owing to patient delay [from onset to the patient visiting a general practitioner (GP)] and medical delay (from the visit to the GP to a visit to a dermatologist), it was not possible to establish the exact onset of disease. Therefore, ensuring that the variables used for matching were unaffected by participation was not feasible. Hence, the quality of the matching was problematic. Various studies have been conducted on the length of delays. Skoet et al. (7) reported a median delay of 2 years (average of > 4 years) for occupational hand eczema from onset until notification to the Board of Occupational Health. For hand eczema in general, the median delay from onset until the patient was seen by a dermatologist was 6 months (3 months of patient delay and 3 months of medical delay), as reported by Hald et al. (8). As a compromise, we chose to match at 1 year prior to testing.
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Table 1. Variables used for matching
Children (0–15 years) Age Sex Geographical origin Cohabitation status Socioeconomic status Education High-risk occupationa Household with childrenb
X X X – – – – –
Non-occupational Occupational contact contact dermatitis dermatitis X X X X X X – –
X X X X X X X X
a Employment in an occupation with a high incidence (hairdressers, dental surgery assistants, bakers, kitchen workers, cooks, and butchers) (8) within 4 years prior to patch testing. b Membership of a household with children.
Table 1 shows the variables that we used for matching. They were primarily basic socio-demographic variables. However, for adults with occupational contact dermatitis, dummies for being in an occupation with a high incidence of contact dermatitis and for being in a household with children were also included, from the perspective that these variables were also strong predictors of contact dermatitis. Controls were selected from a 30% random sample of the population by the use of propensity score matching (6), in which the five nearest neighbours are selected for each case on the basis of the likelihood of disease being present. Controls with a visit to a dermatologist and more than one prescription of steroid lotion [Anatomical Therapeutic Chemical Classification System (ATC) codes beginning with D07] were excluded. Cases and individuals who migrated or died during follow-up were also excluded from the control group before matching. Study design
This study was designed as a register-based cost-of-illness study. The difference between costs for cases and controls was regarded as being attributable to the disease. As the exact onset of disease was not determinable, it was not possible to be certain whether costs were entirely attributable to the disease until after the patient had been tested. Therefore, an approach was chosen whereby yearly ‘attributable’ costs were estimated from 4 years prior to patch testing until 1 year after patch testing, although, for children, it was only 1 year before and 1 year after patch testing, because children included newborns. It was assumed that this period would cover the majority of attributable costs incurred, and that, as the date of patch testing was approached, the frequency of disease in the case group would increase, hence increasing the rate
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of costs attributable to the disease. Healthcare costs and productivity loss for cases and controls were determined for each year and compared. Estimation of costs
Healthcare costs included utilization of primary and secondary healthcare services and prescription medicine. Healthcare costs in the primary healthcare sector were defined as the fees paid from the public health insurance to healthcare professionals for visits and other services. With respect to the secondary healthcare services, the Danish diagnosis-related group (DRG) tariffs, defined as the average cost per admission, were used as the unit cost estimates for admissions. The Danish ambulatory grouping system (DAGS) tariffs, defining the average cost per visit, were used as the unit cost estimates for outpatient or emergency room visits in the secondary healthcare sector. To determine the cost of prescription medicine, the market price was used, including both reimbursement and co-payment parts. Healthcare provision (primary and secondary care) in Denmark is, to a great extent, publicly funded, as 85% of healthcare costs are financed through taxes. Healthcare is mainly provided by the regional authorities. The patients make co-payments for prescription drugs, dentist services, and visits to physiotherapists, chiropractors, etc. The Danish DRG and DAGS charges are used for activity-based funding in the hospital sector. The charges are estimated by the national health authorities on the basis of costing data from Danish hospitals, and the Danish DRG system was initially inspired by the DRG systems developed in the United States. For individuals in the labour market force (aged 18–65 years and excluding individuals who have taken early retirement, retired individuals, and pensioners), productivity costs included long-term sick leave, that is, > 24 days, for both adult cohorts, and the cost of vocational rehabilitation for adults with OCD. An assumption was made that the entire period of benefits (sickness or rehabilitation) represented 100% lost productivity. According to the human capital method, productivity losses were valued at the average earnings of ¤37.4 per hour worked (available from Statistics Denmark). The types of employment with reduced productivity are characterized by varying durations and frequencies. Hence, the burden to society in terms of productivity loss may best be analysed by adding together the weeks of benefits in each category.
database contains information about individuals tested on suspicion of contact dermatitis at one of 12 different clinics (three of which were in hospitals) spread over the entire country. There was one record for each test visit, and each record contained information about the test date, age, sex, and outcome of patch tests performed at the allergy clinics, as well as whether the disease was caused by the occupation. We excluded individuals with multiple test visits. There were 43 733 observations in the database, with the first test being recorded in 1985, and the database is still active. The individual civil registration number in Denmark allows for the connection of information between different registers. The advantages of such register connections have been well illustrated in Davidsen et al. (10). For this study, we used individual encrypted data on healthcare utilization, socio-demographics, education, labour market affiliation, transfer payments, migration and death for the cases identified in the clinical database and for a 30% random selection of the Danish population. These data were supplied and hosted by Statistics Denmark. To describe healthcare utilization, we used data from the Danish National Health Service Register, the Danish National Patient Register, and the Danish National Prescription Registry. These registers hold detailed information about the use of healthcare resources. Danish legislation permits researchers and others to access these registers. To describe labour market affiliation, we used data from the Occupational Classification Module (AKM), which is a model that generates information on the basis of various registers. The information for the analysis of productivity loss was retrieved from the National Labour Market Authority’s longitudinal database DREAM, which holds information on transfer payments for all Danish citizens on a weekly basis. The currency was translated into euros according to a 7.50 DKK/euro exchange rate. Costs were discounted at a 3% discount rate and adjusted to similar price levels (fixed at 2010 price levels). Statistical analysis
Analyses were performed with the statistical package sas 9.2 for Windows (SAS Institute, Cary, NC, USA). The Wilcoxon test was used for comparison of the costs between cases and controls. For any test, a significance level of 5% was chosen (α = 0.05).
Data
Results
Cases were identified in a clinical database run by the National Allergy Research Centre (9). This
Forty-three thousand seven hundred and thirty-three observations were made for 40 201 unique individuals in
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Table 2. Demographics of cases 2004–2009
Children Occupational contact dermatitis Non-occupational contact dermatitis Total
n
Female (%)
Age (years)
1228 2191 18 022 21 441
63 61 66 –
11.6 38.3 46.8 –
the clinical database. Thirty-seven thousand one hundred and ninety-one individuals had only one observation, and of these, 22 376 individuals were incident in the period 2004–2009. Nine hundred and thirty-five individuals had missing information on matching variables. Thus, the final sample for analysis was 21 441, and the majority of these were adults with non-occupational dermatitis. Table 2 shows the sample that was eligible for analysis. The majority of cases were women, and the average age at patch testing and diagnosis in children was 12 years. For adults, the diagnosis was made at 38 years of age in persons with OCD, and at 47 years of age in patients with non-OCD.
For children, however, the attributable healthcare cost decreased from ¤556 at 1 year before recognition to ¤403 at 1 year after, totalling ¤959 for the 2 years. The reduction was especially driven by reductions in inpatient admissions and primary care. Healthcare costs attributable to OCD remained constant for the first 3 years of the study period. However, increases in the year before recognition (primary care and outpatient visits) and the year after (outpatient visits and inpatient admissions) drove up the total attributable healthcare cost from ¤58 in year 2 before recognition to ¤390 in the year after recognition. The total attributable healthcare cost per case of OCD over the entire period was ¤724. For adults with non-OCD, the attributable healthcare cost increased throughout the study period, from ¤215 at 4 years before recognition to ¤561 at 1 year after. The total attributable healthcare cost per case of non-OCD over the entire period was ¤1794. The increase was driven by increases in the secondary care sector escalating towards the end of the study period.
Productivity loss Healthcare costs
Figure 1 and Table 3 shows attributable healthcare costs for the three populations analysed from the 4 years before patch testing (1–4) until the year after patch testing (5). Wilcoxon tests showed that healthcare costs for cases were significantly higher (α = 0.05) than those for their matched controls, with the exception of OCD dermatitis inpatient admissions in years 1, 4, and 5. There was a tendency for attributable healthcare costs to increase, especially as the end of the period was approached.
Figure 2 shows the labour market effects of OCD in terms of weeks with long-term sickness benefits and labour market rehabilitation benefits. The figures are averages for the entire population. The trend for productivity loss was similar to that for healthcare costs: the productivity loss increased towards the end of the study period. Labour market rehabilitation benefits were constant at 0.2 weeks per year until disease recognition, and subsequently increased to 0.8 weeks per year. Long-term sickness benefits increased throughout the period, from 0.5 weeks in year 1 to 3.0 weeks in
Fig. 1. Attributable total healthcare costs per case per period [before (1–4) and after (5) recognition] (2010 euros). OCD, occupational contact dermatitis.
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Table 3. Total healthcare costs per person per period [before (1–4) and after (5) recognition] (2010 euros)
Children
Case
OCD
Control Attributable Case
Non-OCD
Control Attributable Case
Control Attributable
Drugs Primary care Outpatient Inpatient Total Total Total Drugs Primary care Outpatient Inpatient Total Total Total Drugs Primary care Outpatient Inpatient Total Total Total
Years 1
2
3
4
5
– – – – – – – 127 145 181 357 811 765 46 215 188 227 636 1265 1051 215
– – – – – – – 115 146 227 419 906 831 75 227 197 257 688 1369 1137 232
– – – – – – – 114 162 225 416 917 859 58 240 207 312 775 1535 1236 299
92 185 216 425 917 361 556 138 229 331 340 1037 882 155 268 291 431 857 1847 1360 487
79 119 296 282 777 375 403 141 185 658 463 1447 1057 390 265 232 597 1015 2110 1549 561
OCD, occupational contact dermatitis. Results in bold were statistically significant as compared with controls (Wilcoxon, α = 0.05).
Fig. 2. Weeks of benefits attributable to contact dermatitis per case per period [before (1–4) and after (5) recognition] (2010 euros). OCD, occupational contact dermatitis.
year 5. The largest absolute increases occurred in the years before and after recognition. The value of the productivity loss was ¤8498 attributable to sickness and ¤2224 attributable to vocational rehabilitation for the entire period. Non-OCD patients had a much lower attributable productivity loss than OCD patients (data not shown). Thus, long-term sickness benefits increased from 0.3 weeks per year to 0.8 weeks in year 5. The value of the productivity loss for non-OCD patients was ¤3074 attributable to sickness for the entire period.
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Discussion Only a few previous studies have been published on the healthcare costs and productivity loss per case of OCD. In most studies, the costs were based on estimates, but, by the use of nationwide registers, we were able to obtain a high level of detail. For every incident case of OCD or non-OCD for adults and children, the healthcare costs attributable to the disease for the 4 years prior to registration for adults and 1 year for children in the database at the time of patch
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testing and the year after registration were ¤959 for children, ¤724 for OCD, and ¤1794 for non-OCD. In terms of productivity loss, the costs for the same period were ¤10 722 for OCD and ¤3074 for non-OCD. The decrease in children’s attributable healthcare costs after patch testing was consistent with intuition. The diagnosis of contact allergy in children may be challenging, as the clinical picture may be confused with atopic dermatitis for a while, or contact allergy may be a complication in atopic dermatitis, which is hard to recognize in a situation of chronic fluctuating skin disease (11). Therefore, healthcare costs may be high until recognition; however, once the correct diagnosis has been made, the healthcare demand reduces, resulting in less expensive treatment, indicating a clear benefit of patch testing and the subsequent intervention. The healthcare costs for patients diagnosed with OCD were increased as compared with controls in the whole observation period, although only modestly until 1 year prior to patch testing (Fig. 1). It seems that patients may suffer from minor symptoms for some years, and that, when disease worsens, referral to dermatologists is made and patch testing is performed. This fits with data showing that the mean duration of disease was 4 years at the time when it was recognized as occupational by the Danish Board of Industrial Injuries (3). The medical costs continued to rise after patch testing, as the causes and prevention of occupational skin disease are complex, and preventive measure need to be implemented at the workplace, which may take time, meaning that causative exposures cannot always be avoided. In a recent study on occupational hand eczema in Germany, the annual healthcare cost for managing work-related chronic hand eczema was ¤3309 annually (12). This is much more than we found in our study. The populations under study differed, as our study population included all patch tested cases, including those with no current symptoms or minor symptoms, whereas Diepgen et al. based their calculation on patients with refractory work-related hand eczema (12). Long-term sickness and rehabilitation increased just before and after patch testing, and the total cost per person was ¤10 722 for the 5 years of observation. In 2011, 2660 cases of OCD were reported to the Danish Board of Industrial Injuries (13); this would translate into a total cost of productivity loss of ¤28.5 million. In Germany, the productivity losses attributable to OCD are estimated to be more than ¤1.5 billion a year (14), and in the EU they are estimated to be more than ¤5 billion a year (15). These estimates depend on the actual costs in different countries and the quality of the data used for calculations.
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In our study, productivity losses were valued according to the average earnings of ¤37.4 per hour worked available from Statistics Denmark, which corresponds to ¤280.5 for a working day of 7.5 hr, whereas in Germany the cost of one lost working day used for calculations was estimated to range from ¤400 to ¤700 (14). In our study, we only included long-term sickness defined as > 24 days in a row per year, as information about shorter sick leave is not available from the Danish registers. This is likely to have resulted in an underestimation of the costs. In a recent study on patients with occupational hand eczema who entered a rehabilitation programme, 62.9% reported taking sick leave in the previous year, with a mean of 76.4 days (16). In a Swedish 12-year follow-up study on occupational skin disease, 48% of the cohort had taken sick leave of at least 7 days in duration (4), whereas in Germany the average length of sick leave for occupational skin disease was estimated to be 14 days (14). Non-OCD in adults showed larger medical costs than those for OCD for the whole study period, and an increase in costs in year 3 (prior to patch testing), in contrast to OCD, for which the increase mostly occurred after patch testing. The main driver of the increase in attributable costs of non-OCD was secondary care, and the draw on the secondary health sector was made sooner in the observation period than for OCD. This may mean that those with (suspected) OCD are patch tested sooner after referral to the secondary healthcare sector than those with non-OCD, in line with the guidelines on diagnosis of OCD (17), whereas, in non-occupational cases, this may be more up to the individual judgement of the doctor. As we do not know the time of onset, it is not possible to say whether there is more delay in the treatment of one group than in the treeatment of the other. Also, for non-OCD, the loss of productivity costs exceeded the medical costs, so even though the disease was not primarily occupational, functional or social impairments could result in the need for labour market rehabilitation. The total cost per case of non-OCD was ¤3635 over a 5-year period. Non-OCD is much more frequent than OCD, and thus the total cost (¤80 million) was larger than the collective cost for OCD. In a German study of 310 patients with chronic hand eczema, the yearly heathcare cost was approximately two to three times higher for those with occupational hand eczema than for those with non-occupational hand eczema. The costs attributable to productivity loss were also larger in the group with occupational hand eczema (12). This study compared patients with a similar clinical picture, that is, hand eczema, whereas our study population was
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much more heterogeneous, as the inclusion criterion was patch testing, and there were no requirements concerning the clinical presentation. In 2008, the direct cost of contact dermatitis in the EU was estimated to ¤2.3 billion per year (18); if it is assumed that the incidence and cost of non-OCD could be extended from our study to the rest of the EU, the total cost would be ¤6.4 billion. In this study, we calculated the direct costs of illness caused by contact dermatitis in children and adults, and in occupational and non-occupational cases. A matched control group was included, and the difference between the costs for cases and controls was regarded as being attributable to the disease. However, identifying the onset of disease was problematic. We knew the date when patients were seen at a dermatologist for contact dermatitis; however, this has been shown to be delayed to varying extents. Therefore, a compromise was made, and 1 year before patch testing was selected for matching. Matching at any year before patch testing would risk the inclusion of both healthy people and patients with disease in the case group. Some of the rehabilitation is likely to be productive. Therefore, the assumption that the entire period of benefits (sickness or rehabilitation) was lost entirely may lead to an estimate that is too high in the case of vocational rehabilitation. Propensity score matching is used to eliminate baseline differences, in order for differences between a set of populations to be attributed entirely to the disease. The problem with using propensity score matching when the exact onset of disease is not known is that the elimination of baseline differences may be jeopardized. This is the problem with using real-life data rather than performing isolated experiments. If the onset of disease is not known, there is a risk that the information used for matching will have already been affected by the disease. If this is the case, there is a risk that we have not selected a matching set of individuals. Thus, we will not be able to attribute the difference between the groups to the disease. In the present study, there may only be a problem in the case of OCD, in which three variables used for matching (socio-economic status, education, and highrisk occupation) may have been affected if onset did occur prior to matching.
This study covered only the 4 years prior to recognition and 1 year after recognition. Studies have shown that the prognosis of OCD is poor (19–21). Therefore, positive attributable costs may be incurred long after the recognition. Furthermore, we were not able to include OTC drugs and other non-recorded costs. Another important drawback was the lack of information on sick leave for < 24 days in a row in a year. Because of these issues, the estimates given in this study may be considered to be conservative. In estimating the total cost of contact dermatitis, it should be kept in mind that only an estimated 25% of those reporting symptoms of contact dermatitis were patch tested (1) and included in this study.
Conclusions The main findings of this study were that there were statistically significant attributable healthcare costs for both children and adults, and statistically significant productivity losses for adults, in persons with contact dermatitis in comparison to the matched controls. The most important problem that this study faced was identification of the onset of dermatitis, as there may be a long delay from onset until medical attention. This made the determination of the appropriate study period and the quality of the matching problematic.
Acknowledgements This study was performed in collaboration with the National Allergy Research Centre and the Centre for Applied Health Services Research (CAST). The members of the Danish Contact Dermatitis Group and doctors contributing to the data collection are gratefully acknowledged: Niels Kren Veien, Hans Lomholt, Henrik Sølvsten, and Anne Funding (Aalborg); Mette Sommerlund (Aarhus); Niels Henrik Nielsen (Bagsværd); Anne Danielsen, Mads Nielsen, and Rune Lindskov (Copenhagen); Torkil Menn´e (Gentofte); Aksel Otkjær, Knud Kaaber, and Morten Østerballe (Herning); Susanne Vissing (Hørsholm); Berit Kristensen and Ove Kristensen (Kalundborg); Klaus Ejner Andersen and Evy Paulsen (Odense), Christian Avnstorp, Anne Hjorther, and Bent Staberg (Rødovre); Bo Lastein Andersen (Svendborg); and Jens Thormann and Henrik Thormann (Vejle).
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