The Occupational History in the Primary Care Setting DAVIDA. SCHWARTZ,M.D., M.P.H., DOUGLASS. WAKEFIELD,Ph.D., JOHNF. FIESELMANN,M.D., MARYBERGER-WESLEY,R.N., M.S.N., RODNEYZEITLER, M.D., Iowa City, Iowa
PURPOSE: To assess the need for services in occupational medicine, we determined the prevalence of reported occupational exposures in patients seen in the primary care setting. In addition, we evaluated the validity of our survey
instrnment. P A T I E N T S A N D METHODS: A l l
patients (n
=
1,112) seen over a 3-month period of time in the PrimAry Care Clinic at the Iowa City Vetersns
Affairs Medical Center were considered eligible for this study. A survey instrmnent was developed to obtain specific inform~tiqn regarding occupational exposures. The questionnni~'e was 8dmini~tered to 534 or 48% of all eligible patients. The validity of the survey instrument was evaluated by comparing chest radiographs in subjects with a history of exposure to asbestos, coal dust, or silica to those in patients who were not exposed to any of these agents. RESULTS: We found that Almost 75% of the patients reported prior occupational exposure to at least one potentially toxic agent, and over 30% clnimed exposure to at least four potentinlly toxic agents. The validation study indicated that the reported exposure history for asbestos, coal dust, and silica is significantly associated with anticipated changes on chest radiographs. These rmdings suggest that this easily administered survey instrument is valid for pneumoconiotic dust exposures and may also be valid for other potentially toxic exposures. CONCLUSION: Data from our study indicate that patients seen in the ambulatory care setting may have clinically significant occupationRI exposuros that are relevant to their medical condition. From the Pulmonary Disease Division, Department of Internal Medicine (DAS, JFF), the Division of General Internal Medicine, Department of Internal Medicine (RZ), the Graduate Program of Hospital and Health Administration (DSW), and the Iowa City Veterans Affairs Medical Center (MB-W), University of Iowa, College of Medicine, iowa City, Iowa. This study was supported in part by the Department of Veterans Affairs Health Services Research and Development Field Program at the Iowa City Veterans Administration Medical Center. Dr. Schwartz is a recipient of a Clinical Investigator Award (ES00203) from the National Institute of Environmental Health Sciences. Requests for reprints should be addressed to David A. Schwartz, M.D., M.P.H., Pulmonary Disease Division, Department of Internal Medicine, University of Iowa, College of Medicine, Iowa City, Iowa 52242. Manuscript submitted May 25, 1990, and accepted in revised form November 19, 1990.
ccupational exposures are clearly responsible O for a portion of acute and chronic medical conditions in the general population [1,2]. Although precise incidence and prevalence data are unavailable, the National Research Council [3] and the Bureau of Labor Statistics [4] estimate that in 1984, occupational exposures were responsible for approximately 125,000 illnesses, 5.3 million injuries, and between 4,000 and 12,000 deaths. However, the long latency period between exposure and disease, the multifactorial etiology of chronic diseases, the lack of recognition of occupational disease by physicians, and the underreporting of occupational disease underscore the concern that even these numbers underestimate the potential clinical significance of occupational exposures in the development of chronic diseases [2]. While acknowledging these uncertainties, the Institute of Medicine has recently advocated for the expansion of occupational medicine services in the United States [2]. However, firm clinical data justifying these needs are unavailable and the extent and type of occupational medicine services needed to address these concerns have not been clearly established. To further assess the need for services in occupational medicine in the ambulatory setting, we determined the prevalence of reported previous occupational exposures in a large cohort of outpatients. We were particularly interested in defining the types of exposures and in assessing the validity of the survey instrument.
PATIENTS AND METHODS Patient Population All patients seen in the Primary Care Clinic at the Department of Veterans Affairs Medical Center in Iowa City between January 1 and March 31, 1989, were considered eligiblefor this study. During these 3 months, 1,112 patients were seen in the Primary Care Clinic and 534 or 48% completed the questionnaire. Although attempts were made to survey allof the patients, the completion of the questionnaire was dependent on the cooperation of nursing service personnel and the examining physician. To our knowledge, no systematic bias was associated with the completion of the questionnaire. However, it is possible that acutely ill patients who required immediate action to address their medical condition are underrepresented in our study population. DeMarch 1991
The American Journal of Medicine Volume 90
315"
OCCUPATIONAL HISTORY / SCHWARTZ ET AL
TABLE I Comparisonof PatientsSurveyedVersusAll PatientsSeen in the AmbulatoryCare Clinic* All Patients Patient visits Visits by month January February March Age (years) Gender Male Female Smoking history Never Former Current
1,112
Patients Surveyed 534
312 (28.1%) 467 (42.0%) 333 (29,9%) 56.7 4. 14.0
125 (23.4%) 268 (50.2%) 141 (26.4%) 56.5 4. 13.9
1,096 (98.6%) 16 (1.4%)
528 (98.9%) 6 (1.1%)
425 (38.2*/,) 237 (21.3%) 426 (38.3*/,)
213 (39.9%) 110 (20.6%) 202 (37.8%)
Valuesreportedrepresentthe mean± standarddeviationfor continuousvariables,and number(%) for categoricdata. TABLE II
Occupational History for the Surveyed Patients* Employment status Employed Retired Years employed in current job Years employed in previous job Is your health problem related to your work? Yes Do fellow workers have similar health problems ? Yes
317 (59.4%) 217 (40.6%) 15.3 4- 15.4 19.1 4- 13.5 88(16.5%) 40 (7.5%)
' Valuesreportedrepresentthe mean:t: standarddeviationfor continuousvariables,and , number(%) for categoricdata.
spite these reservations, only a small portion of our ambulatory population would have been too ill to complete the questionnaire. The age, gender, and smoking history are similar between those who completed the questionnaire and all patients seen in the Primary Care Clinic (Table I). Survey Instrument
Our questionnaire was a nurse- and physicianadministered survey instrument that was designed to be easy to use, included potentially relevant occupationai exposures, and required no more than 5 minutes to complete. We obtained specific information regarding the patients' demographic characteristics, current job, three previous jobs, and occupat i o n a l e x p o s u r e s . I n c l u d e d in t h e l i s t of occupational exposures were general agents (chemicai fumes, solvents, pesticides, and heavy metals), respiratory toxins (asbestos, coal dust, silica, grain dust, and welding fumes), and physical factors (repetitive motion, noise, radiation, and extreme temperatures). Patients were permitted to identify as many exposures as they thought were relevant to their specific career. Because of the pilot nature of this study, no weighting in terms of intensity or duration of the exposure was attempted. 316
March 1991
The American Journal of Medicine
Volume 90
Validation Component To evaluate the validity of the survey instrument, we divided the study population into those who claimed occupational exposure to at least one fibrogenic agent such as asbestos, silica, or coal dust (n = 136) and those who did not report having exposure to any of these agents (n = 398). Next, we identified all patients who had claimed exposure to a fibrogenic agent (i.e., asbestos, silica, or coal dust) and had a chest radiograph obtained within 2 years of the study (n = 112). A similar number of individuals (n = 112) were randomly selected from all subjects who denied exposure to these agents and had a chest radiograph within 2 years of the study. The posteroanterior chest film was interpreted by one trained reader, unaware of the exposure status and who used the International Labor Organization (ILO) 1980 guidelines for classification of pneumoconioses [5]. The chest roentgenogram was considered abnormal if the worker had either parenchyreal fibrosis or a pleural abnormality. Parenchymal fibrosis was defined as an ILO score of at least 1/0, which represents the lower limit of detection for fibrosis in the ILO classification system [5]. Pleural disease was defined as the presence of at least one of the following characteristics: (1) diffuse pleural thickening of the chest walls; (2) pleural calcification of the chest walls and/or diaphragm; or (3) pleural or diaphragmatic plaque. Bilateral pleural fibrosis, although more specific for asbestos-induced pleural disease, was not required for a chest radiograph to be interpreted as showing "pleural disease." Other abnormalities on the chest roentgenogram, such as lung nodules, infiltrates, and pleurai effusions, were noted, but did not influence the ILO classification of parenchymai fibrosis or pleural disease. Data Analysis
Since this study is largely descriptive, we have decided to simply present the descriptive statistics. We have used Fisher's exact test [6] to analyze the valid]-ty component of this study. Relative risks were estimated by the odds ratio, and we calculated exact 95% confidence intervals for each estimate [7]. RESULTS
Within the patient population that completed the questionnaire (n = 534), Mmost all individuals were male and the average age was 56 years. Of interest, we found that 59% of the patients were actively employed at the time of the examination (Table II). Although this is somewhat lower than national statistics for employment among men, these results suggest that a substantial portion of
OCCUPATIONAL HISTORY / SCHWARTZ ET AL
the Veterans Affairs patient population are potenTABLE III tially at risk of ongoing occupational exposures. Occupational Category* for Surveyed Patients Moreover, on average, these patients claimed to be employed for 15 years in their current job and 19 Occupational Category Number (%) years in their previous job (Table II). This suggests Professional 20 (3.7) stability in employment status and points to the Services 130 (24.3) Laborer 90 (16.9) potential for long-term occupational exposures. AlMechanic 33 (6.2) most 17% of the patients thought that their health Maintenance 18 (3.3) Construction 81 (15.2) problems were related to occupational exposures, Agriculture 41 (7.7) and nearly 8% were concerned that fellow workers Transportation 33 (6.2) Unknown 88 (16.5) had similar medical conditions (Table II). Tables III and IV list the current, or for those "The 1980U.S.Bureauof Censusclassificationsystem[8] wasusedto codeoccupation industryfor eachjob, and thissystemwas usedto developthe aboveoccupational who were retired, most recent, occupational cate- and categories.The currentjobwasusedfor thosesubjeclswhowereactivelyemployed,and for those gory and occupational exposures for our study sub- category. retired subjectsthe most recent job was used to determineoccupational jects. Most of our subjects were blue collar workers. Over 50% of the workers were involved in either the construction or agriculture industries or employed as laborers, mechanics, or maintenance workers. TABLE IV This is particularly important since a large portion Occupational Exposures for Surveyed Patients of blue collar workers in general can be expected to be exposed to potentially dangerous dusts, fumes, Number of chemicals, and physical agents. In-fact, Table IV Patients demonstrates that at least 25% of all patients Exposures Exposed(%) claimed occupational exposure to chemical fumes, General solvents, pesticides, grain dust, welding fumes, Chemical fumes 189 (35.4) Solvents 156 (29.2) noise, or extremes in temperature. Almost 75% of Pesticides 135 (25.3) the patients had prior occupational exposure to at Heavy metals 106 (19.9) Respiratory least one potentially toxic agent (i.e., asbestos, Asbestos 105 (19.7) heavy metals, etc.) and over 30% claimed exposure Coal dust 55 (10.3) Silica 32 (6.0) to a minimum of four of these agents (Figure 1). Grain dust 152 (28.5) To determine the validity of the exposure history, Weldingfumes 157 (29.4) Physical we examined the chest films of those who claimed Repetitive motion 70 (13. I) occupational exposure to either asbestos, coal dust, Noise 233 (43.6) Radiation 32 (6.0) or silica and compared these interpretations to Heat/cold 163 (30.5) films in patients who did not have exposure to any
40 35
A
30 25
0 *3
20
g
15
I1.
10
O Figure 1. Frequency distribution for the cumulative number of exposures for all 534 study subjects.
1
O
2
3
>4
Number of Exposures by History
March 1991
The American Journal of Medicine
Volume 90
317
OCCUPATIONALHISTORY/ SCHWARTZET AL TABLEY Comparison of Chest Radiograph Readingsin Personswith Exposuresto Fibrogenic Agents (Asbestos, Coal Dust, and Silica) and Those Without Any Exposureto These Agents Reported Exposureto Fibrogenic Al~ents Yes Total radiographs read Interstitial fibrosis(>__ 1/0) = Pleural abnormalities
112 12(10.7%) 16 (14.3%)
No 112 4(3.6%) 2 (1.8%)
Relative Risk (95% CI)
p Value
-3.2(0.9, 14.2) 9.8 (2.2, 89.6)
-0.07 0.001
CI = confidence interval. " 1/0 represents the lowest grade of interstitial lung disease using the International Labor Organization classification system [5].
one of these agents (Table V). Although the risk of tions and diagnostic tests that might identify a dishaving radiographic evidence of interstitial fibrosis ease in the preclinical and potentially treatable was greater for the exposed subjects (10.7%) than state. Earlier identification of occupational expofor the unexposed subjects (3.6%), this difference sures as the cause of medical problems may reduce did not achieve statistical significance. Similarly, associated morbidity, functional limitations, morpl~ural abnormalities were more common among tality, and health care costs. Second, identification those who had been exposed to either asbestos, coal of an exposure-disease relationship may result in dust, or silica than among those patients who curing or stabilizing the disease by mitigating the claimed no prior exposure (14.3% versus 1.8%). In effect of the exposure by diminishing contact with fact, these chest wall lesions proved to be signifi- the offending agent. Furthermore, identification of cantly related to previous exposure to asbestos (p --- occupational exposures could serve as a stimulus to 0.001). Further analyses indicate that among ex- identify fellow workers with similar exposures and posed subjects, the chest wall abnormalities were ultimately could result in efforts to diminish avoidexclusively observed among those who claimed to able exposures at the work site. This may involve have worked with asbestos. These findings provide job relocation or modification when only a single p r e l i m i n a r y v a l i d a t i o n of o u r e x p o s u r e worker is affected or plant or work process modifiquestionnaire. cation when several workers are similarly affected. Finally, identification of an exposure-disease relaCOMMENTS tionship should promote the filing of workers' comResults from our study indicate that patients pensation claims that would appropriately transfer seen in the ambulatory care setting may have his- the financing of care for occupationally related distories of occupational exposures that are relevant to eases to the workers' compensation system. their clinical presentation. In fact, only 28% of the From the perspective of physician education, our patients claimed not to be exposed to any one of findings clearly demonstrate that relevant clinical these potentially detrimental agents, whereas more data can be obtained from an exposure questionthan 30% of our study subjects claimed exposure to naire that is easy to administer in the outpatient at least four potentially toxic agents. These findings setting. The utility of the information relies on the support the recent conclusions of the Institute of physician's ability to identify the connection beMedicine [2] and provide data that encourage the tween exposures and diseases. Thus, medical development and expansion of occupational medi- schools and residency training programs need to cine services in the primary care setting. consider the occupational and environmental deA clearly defined exposure history can benefit the terminants of disease as potentially important aspatient in several ways. First, identification of spe- pects of education and training. cific occupational exposures should raise specific During the process of applying our questionnaire, clinical concerns and direct the physician to look for there was little interest from the house officers. particular symptoms and signs, as well as unique They viewed completion of the questionnaire as an diseases. For example, asbestos can cause intersti- additional obstacle impeding patient flow in an altial fibrosis and malignancies of the lung and pleu- ready busy clinic. This is unfortunate based on the ra; exposure to grain dust and other agricultural potential diagnostic and therapeutic utility of this dusts can cause asthma and bronchitis; and exces- additional information. The potential exposuresive exposure to noise can result in clinically signifi- disease association appears to be great enough to cant hearing loss. Thus, if a specific exposure is warrant the relatively short time commitment to noted, this should lead to a logical series of ques- obtain this information. Our study indicates that 318
March 1991 The American Journal of Medicine Volume 90
OCCUPATIONAL HISTORY / SCHWARTZ ET AL
our questionnaire can be easily administered in the ambulatory care setting in less than 5 minutes and gathers clinically useful exposure information. Moreover, the high proportion of patients reporting occupational exposures indicates that additional emphasis should be placed on developing expertise in occupational medicine among primary care clinicians. In particular, ambulatory-based residency training programs need to enhance existing methods and expertise in teaching physicians how to efficiently obtain and effectivelyutilize occupational exposure data. Our study was based at a Veterans Affairs Medical Center and the results may not be generalizable to other medical communities. However, since the veterans largely consist of blue collar workers, results from this investigation may be applicable to nonveteran blue collar workers. Clearly, additional studies are needed to assess the clinical relevance of
an occupational history in other primary care settings.
REFERENCES 1. Cullen MR, Cherniack MG, Rosenstock L. Occup Med 1990; 321: 594-601, 675-83. 2. Role of the primary care physician in occupational and environmental medicine. Institute of Medicine. Washington: National Academic Pressl 1988. 3. National ResearchCouncil. Counting injuries and illnessesin the workplace-proposals for a better system. Washington: National Academic Press, 1987. 4. Bureau of Labor Statistics. Occupational injuries and illnesses in the U.S. by industry. U.S. Department of Labor Bulletin, 1986. 5. International Labor Office, Geneva, Switzerland. Guidelines for the use of International Labor Organization (ILO) international classification of radiographs of pneurnoconioses. Revised ed. Geneva, 1980. 6. Colton T. Statistics in medicine. Boston: Little Brown, 1974. 7. Mehta CR, Patel NR, Gray R. Computing an exact confidence interval for the common odds radio in several 2 X's contingency tables. J Am Stat Assoc 1985; 78: 969-73. 8. Bureau of the Census. Index of industries and occupations. Washington: U.S. Department of Commerce, 1980.
March 1991 The American Journal of Medicine Volume 90
319
PURPOSE: To assess the need for services in occupational medicine, we determined the prevalence of reported occupational exposures in patients seen in the primary care setting. In addition, we evaluated the validity of our survey
instrnment. P A T I E N T S A N D METHODS: A l l
patients (n
=
1,112) seen over a 3-month period of time in the PrimAry Care Clinic at the Iowa City Vetersns
Affairs Medical Center were considered eligible for this study. A survey instrmnent was developed to obtain specific inform~tiqn regarding occupational exposures. The questionnni~'e was 8dmini~tered to 534 or 48% of all eligible patients. The validity of the survey instrument was evaluated by comparing chest radiographs in subjects with a history of exposure to asbestos, coal dust, or silica to those in patients who were not exposed to any of these agents. RESULTS: We found that Almost 75% of the patients reported prior occupational exposure to at least one potentially toxic agent, and over 30% clnimed exposure to at least four potentinlly toxic agents. The validation study indicated that the reported exposure history for asbestos, coal dust, and silica is significantly associated with anticipated changes on chest radiographs. These rmdings suggest that this easily administered survey instrument is valid for pneumoconiotic dust exposures and may also be valid for other potentially toxic exposures. CONCLUSION: Data from our study indicate that patients seen in the ambulatory care setting may have clinically significant occupationRI exposuros that are relevant to their medical condition. From the Pulmonary Disease Division, Department of Internal Medicine (DAS, JFF), the Division of General Internal Medicine, Department of Internal Medicine (RZ), the Graduate Program of Hospital and Health Administration (DSW), and the Iowa City Veterans Affairs Medical Center (MB-W), University of Iowa, College of Medicine, iowa City, Iowa. This study was supported in part by the Department of Veterans Affairs Health Services Research and Development Field Program at the Iowa City Veterans Administration Medical Center. Dr. Schwartz is a recipient of a Clinical Investigator Award (ES00203) from the National Institute of Environmental Health Sciences. Requests for reprints should be addressed to David A. Schwartz, M.D., M.P.H., Pulmonary Disease Division, Department of Internal Medicine, University of Iowa, College of Medicine, Iowa City, Iowa 52242. Manuscript submitted May 25, 1990, and accepted in revised form November 19, 1990.
ccupational exposures are clearly responsible O for a portion of acute and chronic medical conditions in the general population [1,2]. Although precise incidence and prevalence data are unavailable, the National Research Council [3] and the Bureau of Labor Statistics [4] estimate that in 1984, occupational exposures were responsible for approximately 125,000 illnesses, 5.3 million injuries, and between 4,000 and 12,000 deaths. However, the long latency period between exposure and disease, the multifactorial etiology of chronic diseases, the lack of recognition of occupational disease by physicians, and the underreporting of occupational disease underscore the concern that even these numbers underestimate the potential clinical significance of occupational exposures in the development of chronic diseases [2]. While acknowledging these uncertainties, the Institute of Medicine has recently advocated for the expansion of occupational medicine services in the United States [2]. However, firm clinical data justifying these needs are unavailable and the extent and type of occupational medicine services needed to address these concerns have not been clearly established. To further assess the need for services in occupational medicine in the ambulatory setting, we determined the prevalence of reported previous occupational exposures in a large cohort of outpatients. We were particularly interested in defining the types of exposures and in assessing the validity of the survey instrument.
PATIENTS AND METHODS Patient Population All patients seen in the Primary Care Clinic at the Department of Veterans Affairs Medical Center in Iowa City between January 1 and March 31, 1989, were considered eligiblefor this study. During these 3 months, 1,112 patients were seen in the Primary Care Clinic and 534 or 48% completed the questionnaire. Although attempts were made to survey allof the patients, the completion of the questionnaire was dependent on the cooperation of nursing service personnel and the examining physician. To our knowledge, no systematic bias was associated with the completion of the questionnaire. However, it is possible that acutely ill patients who required immediate action to address their medical condition are underrepresented in our study population. DeMarch 1991
The American Journal of Medicine Volume 90
315"
OCCUPATIONAL HISTORY / SCHWARTZ ET AL
TABLE I Comparisonof PatientsSurveyedVersusAll PatientsSeen in the AmbulatoryCare Clinic* All Patients Patient visits Visits by month January February March Age (years) Gender Male Female Smoking history Never Former Current
1,112
Patients Surveyed 534
312 (28.1%) 467 (42.0%) 333 (29,9%) 56.7 4. 14.0
125 (23.4%) 268 (50.2%) 141 (26.4%) 56.5 4. 13.9
1,096 (98.6%) 16 (1.4%)
528 (98.9%) 6 (1.1%)
425 (38.2*/,) 237 (21.3%) 426 (38.3*/,)
213 (39.9%) 110 (20.6%) 202 (37.8%)
Valuesreportedrepresentthe mean± standarddeviationfor continuousvariables,and number(%) for categoricdata. TABLE II
Occupational History for the Surveyed Patients* Employment status Employed Retired Years employed in current job Years employed in previous job Is your health problem related to your work? Yes Do fellow workers have similar health problems ? Yes
317 (59.4%) 217 (40.6%) 15.3 4- 15.4 19.1 4- 13.5 88(16.5%) 40 (7.5%)
' Valuesreportedrepresentthe mean:t: standarddeviationfor continuousvariables,and , number(%) for categoricdata.
spite these reservations, only a small portion of our ambulatory population would have been too ill to complete the questionnaire. The age, gender, and smoking history are similar between those who completed the questionnaire and all patients seen in the Primary Care Clinic (Table I). Survey Instrument
Our questionnaire was a nurse- and physicianadministered survey instrument that was designed to be easy to use, included potentially relevant occupationai exposures, and required no more than 5 minutes to complete. We obtained specific information regarding the patients' demographic characteristics, current job, three previous jobs, and occupat i o n a l e x p o s u r e s . I n c l u d e d in t h e l i s t of occupational exposures were general agents (chemicai fumes, solvents, pesticides, and heavy metals), respiratory toxins (asbestos, coal dust, silica, grain dust, and welding fumes), and physical factors (repetitive motion, noise, radiation, and extreme temperatures). Patients were permitted to identify as many exposures as they thought were relevant to their specific career. Because of the pilot nature of this study, no weighting in terms of intensity or duration of the exposure was attempted. 316
March 1991
The American Journal of Medicine
Volume 90
Validation Component To evaluate the validity of the survey instrument, we divided the study population into those who claimed occupational exposure to at least one fibrogenic agent such as asbestos, silica, or coal dust (n = 136) and those who did not report having exposure to any of these agents (n = 398). Next, we identified all patients who had claimed exposure to a fibrogenic agent (i.e., asbestos, silica, or coal dust) and had a chest radiograph obtained within 2 years of the study (n = 112). A similar number of individuals (n = 112) were randomly selected from all subjects who denied exposure to these agents and had a chest radiograph within 2 years of the study. The posteroanterior chest film was interpreted by one trained reader, unaware of the exposure status and who used the International Labor Organization (ILO) 1980 guidelines for classification of pneumoconioses [5]. The chest roentgenogram was considered abnormal if the worker had either parenchyreal fibrosis or a pleural abnormality. Parenchymal fibrosis was defined as an ILO score of at least 1/0, which represents the lower limit of detection for fibrosis in the ILO classification system [5]. Pleural disease was defined as the presence of at least one of the following characteristics: (1) diffuse pleural thickening of the chest walls; (2) pleural calcification of the chest walls and/or diaphragm; or (3) pleural or diaphragmatic plaque. Bilateral pleural fibrosis, although more specific for asbestos-induced pleural disease, was not required for a chest radiograph to be interpreted as showing "pleural disease." Other abnormalities on the chest roentgenogram, such as lung nodules, infiltrates, and pleurai effusions, were noted, but did not influence the ILO classification of parenchymai fibrosis or pleural disease. Data Analysis
Since this study is largely descriptive, we have decided to simply present the descriptive statistics. We have used Fisher's exact test [6] to analyze the valid]-ty component of this study. Relative risks were estimated by the odds ratio, and we calculated exact 95% confidence intervals for each estimate [7]. RESULTS
Within the patient population that completed the questionnaire (n = 534), Mmost all individuals were male and the average age was 56 years. Of interest, we found that 59% of the patients were actively employed at the time of the examination (Table II). Although this is somewhat lower than national statistics for employment among men, these results suggest that a substantial portion of
OCCUPATIONAL HISTORY / SCHWARTZ ET AL
the Veterans Affairs patient population are potenTABLE III tially at risk of ongoing occupational exposures. Occupational Category* for Surveyed Patients Moreover, on average, these patients claimed to be employed for 15 years in their current job and 19 Occupational Category Number (%) years in their previous job (Table II). This suggests Professional 20 (3.7) stability in employment status and points to the Services 130 (24.3) Laborer 90 (16.9) potential for long-term occupational exposures. AlMechanic 33 (6.2) most 17% of the patients thought that their health Maintenance 18 (3.3) Construction 81 (15.2) problems were related to occupational exposures, Agriculture 41 (7.7) and nearly 8% were concerned that fellow workers Transportation 33 (6.2) Unknown 88 (16.5) had similar medical conditions (Table II). Tables III and IV list the current, or for those "The 1980U.S.Bureauof Censusclassificationsystem[8] wasusedto codeoccupation industryfor eachjob, and thissystemwas usedto developthe aboveoccupational who were retired, most recent, occupational cate- and categories.The currentjobwasusedfor thosesubjeclswhowereactivelyemployed,and for those gory and occupational exposures for our study sub- category. retired subjectsthe most recent job was used to determineoccupational jects. Most of our subjects were blue collar workers. Over 50% of the workers were involved in either the construction or agriculture industries or employed as laborers, mechanics, or maintenance workers. TABLE IV This is particularly important since a large portion Occupational Exposures for Surveyed Patients of blue collar workers in general can be expected to be exposed to potentially dangerous dusts, fumes, Number of chemicals, and physical agents. In-fact, Table IV Patients demonstrates that at least 25% of all patients Exposures Exposed(%) claimed occupational exposure to chemical fumes, General solvents, pesticides, grain dust, welding fumes, Chemical fumes 189 (35.4) Solvents 156 (29.2) noise, or extremes in temperature. Almost 75% of Pesticides 135 (25.3) the patients had prior occupational exposure to at Heavy metals 106 (19.9) Respiratory least one potentially toxic agent (i.e., asbestos, Asbestos 105 (19.7) heavy metals, etc.) and over 30% claimed exposure Coal dust 55 (10.3) Silica 32 (6.0) to a minimum of four of these agents (Figure 1). Grain dust 152 (28.5) To determine the validity of the exposure history, Weldingfumes 157 (29.4) Physical we examined the chest films of those who claimed Repetitive motion 70 (13. I) occupational exposure to either asbestos, coal dust, Noise 233 (43.6) Radiation 32 (6.0) or silica and compared these interpretations to Heat/cold 163 (30.5) films in patients who did not have exposure to any
40 35
A
30 25
0 *3
20
g
15
I1.
10
O Figure 1. Frequency distribution for the cumulative number of exposures for all 534 study subjects.
1
O
2
3
>4
Number of Exposures by History
March 1991
The American Journal of Medicine
Volume 90
317
OCCUPATIONALHISTORY/ SCHWARTZET AL TABLEY Comparison of Chest Radiograph Readingsin Personswith Exposuresto Fibrogenic Agents (Asbestos, Coal Dust, and Silica) and Those Without Any Exposureto These Agents Reported Exposureto Fibrogenic Al~ents Yes Total radiographs read Interstitial fibrosis(>__ 1/0) = Pleural abnormalities
112 12(10.7%) 16 (14.3%)
No 112 4(3.6%) 2 (1.8%)
Relative Risk (95% CI)
p Value
-3.2(0.9, 14.2) 9.8 (2.2, 89.6)
-0.07 0.001
CI = confidence interval. " 1/0 represents the lowest grade of interstitial lung disease using the International Labor Organization classification system [5].
one of these agents (Table V). Although the risk of tions and diagnostic tests that might identify a dishaving radiographic evidence of interstitial fibrosis ease in the preclinical and potentially treatable was greater for the exposed subjects (10.7%) than state. Earlier identification of occupational expofor the unexposed subjects (3.6%), this difference sures as the cause of medical problems may reduce did not achieve statistical significance. Similarly, associated morbidity, functional limitations, morpl~ural abnormalities were more common among tality, and health care costs. Second, identification those who had been exposed to either asbestos, coal of an exposure-disease relationship may result in dust, or silica than among those patients who curing or stabilizing the disease by mitigating the claimed no prior exposure (14.3% versus 1.8%). In effect of the exposure by diminishing contact with fact, these chest wall lesions proved to be signifi- the offending agent. Furthermore, identification of cantly related to previous exposure to asbestos (p --- occupational exposures could serve as a stimulus to 0.001). Further analyses indicate that among ex- identify fellow workers with similar exposures and posed subjects, the chest wall abnormalities were ultimately could result in efforts to diminish avoidexclusively observed among those who claimed to able exposures at the work site. This may involve have worked with asbestos. These findings provide job relocation or modification when only a single p r e l i m i n a r y v a l i d a t i o n of o u r e x p o s u r e worker is affected or plant or work process modifiquestionnaire. cation when several workers are similarly affected. Finally, identification of an exposure-disease relaCOMMENTS tionship should promote the filing of workers' comResults from our study indicate that patients pensation claims that would appropriately transfer seen in the ambulatory care setting may have his- the financing of care for occupationally related distories of occupational exposures that are relevant to eases to the workers' compensation system. their clinical presentation. In fact, only 28% of the From the perspective of physician education, our patients claimed not to be exposed to any one of findings clearly demonstrate that relevant clinical these potentially detrimental agents, whereas more data can be obtained from an exposure questionthan 30% of our study subjects claimed exposure to naire that is easy to administer in the outpatient at least four potentially toxic agents. These findings setting. The utility of the information relies on the support the recent conclusions of the Institute of physician's ability to identify the connection beMedicine [2] and provide data that encourage the tween exposures and diseases. Thus, medical development and expansion of occupational medi- schools and residency training programs need to cine services in the primary care setting. consider the occupational and environmental deA clearly defined exposure history can benefit the terminants of disease as potentially important aspatient in several ways. First, identification of spe- pects of education and training. cific occupational exposures should raise specific During the process of applying our questionnaire, clinical concerns and direct the physician to look for there was little interest from the house officers. particular symptoms and signs, as well as unique They viewed completion of the questionnaire as an diseases. For example, asbestos can cause intersti- additional obstacle impeding patient flow in an altial fibrosis and malignancies of the lung and pleu- ready busy clinic. This is unfortunate based on the ra; exposure to grain dust and other agricultural potential diagnostic and therapeutic utility of this dusts can cause asthma and bronchitis; and exces- additional information. The potential exposuresive exposure to noise can result in clinically signifi- disease association appears to be great enough to cant hearing loss. Thus, if a specific exposure is warrant the relatively short time commitment to noted, this should lead to a logical series of ques- obtain this information. Our study indicates that 318
March 1991 The American Journal of Medicine Volume 90
OCCUPATIONAL HISTORY / SCHWARTZ ET AL
our questionnaire can be easily administered in the ambulatory care setting in less than 5 minutes and gathers clinically useful exposure information. Moreover, the high proportion of patients reporting occupational exposures indicates that additional emphasis should be placed on developing expertise in occupational medicine among primary care clinicians. In particular, ambulatory-based residency training programs need to enhance existing methods and expertise in teaching physicians how to efficiently obtain and effectivelyutilize occupational exposure data. Our study was based at a Veterans Affairs Medical Center and the results may not be generalizable to other medical communities. However, since the veterans largely consist of blue collar workers, results from this investigation may be applicable to nonveteran blue collar workers. Clearly, additional studies are needed to assess the clinical relevance of
an occupational history in other primary care settings.
REFERENCES 1. Cullen MR, Cherniack MG, Rosenstock L. Occup Med 1990; 321: 594-601, 675-83. 2. Role of the primary care physician in occupational and environmental medicine. Institute of Medicine. Washington: National Academic Pressl 1988. 3. National ResearchCouncil. Counting injuries and illnessesin the workplace-proposals for a better system. Washington: National Academic Press, 1987. 4. Bureau of Labor Statistics. Occupational injuries and illnesses in the U.S. by industry. U.S. Department of Labor Bulletin, 1986. 5. International Labor Office, Geneva, Switzerland. Guidelines for the use of International Labor Organization (ILO) international classification of radiographs of pneurnoconioses. Revised ed. Geneva, 1980. 6. Colton T. Statistics in medicine. Boston: Little Brown, 1974. 7. Mehta CR, Patel NR, Gray R. Computing an exact confidence interval for the common odds radio in several 2 X's contingency tables. J Am Stat Assoc 1985; 78: 969-73. 8. Bureau of the Census. Index of industries and occupations. Washington: U.S. Department of Commerce, 1980.
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