American Journal of Emergency Medicine 33 (2015) 674–676
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Original Contribution
Clinical profile of injection drug users presenting to the ED Daniel R. Kievlan, MD, Meri Gukasyan, BS, Julie Gesch, MD, Robert M. Rodriguez, MD ⁎ Department of Emergency Medicine, The University of California San Francisco, San Francisco, CA
a r t i c l e
i n f o
Article history: Received 1 December 2014 Received in revised form 10 February 2015 Accepted 10 February 2015
a b s t r a c t Background: Injection drug users (IDUs) commonly use the emergency department (ED) as their primary health care access point. Objective: We sought to characterize infectious disease clinical presentations and laboratory results of IDUs admitted to the hospital from the ED and contrast them with those of non-IDUs. Methods: We enrolled all admitted adult patients with infectious disease–related diagnoses at a county level 1 trauma center from June 2010 to January 2011 and used a structured chart abstraction tool to record patient characteristics and clinical outcomes. We compared clinical presenting features, laboratory data, and microbiological culture results of IDUs with concomitantly enrolled non-IDUs. Results: Of 603 total participants, 189 were IDUs, and 414 were non-IDUs. Injection drug users had higher rates of skin and soft tissue infection admission but had similar hospital length of stay (7.5 vs 6.1 days) and mortality (2.1% vs 2.9%). Compared with non-IDUs, IDUs more commonly had hyponatremia, 38.1% vs 27.1% (mean difference, 11.4%; 95% confidence intervals [CIs], 3.4%-19.6%) and thrombocytopenia, 18.5% vs 11.0% (mean difference, 7.5%; 95% CI, 1.5%-14.2%) but less frequently had leukocytosis, 36.0% vs 52.7% (mean difference, 16.7%; 95% CI, 8.2%-24.8%). Injection drug users and non-IDUs had similar rates of positive ED-derived blood cultures, 16.5% vs 22.6% (mean difference, 6.1%; 95% CI, −13.3 to 1.7%). Conclusions: When admitted from the ED for infectious disease–related diagnoses, IDUs had similar rates of fever, higher rates of hyponatremia and thrombocytopenia, and lower rates of leukocytosis than non-IDUs. Although they had similar rates of bacteremia, only IDUs were positive for methicillin-resistant Staphylococcus aureus. © 2015 Elsevier Inc. All rights reserved.
1. Introduction Injection drug users (IDUs), who are at significant risk for numerous serious, high morbidity and mortality infections, disproportionately use the emergency department (ED) for health care needs [1-3]. Because of greater risk for occult serious illness, current evaluation and management protocols for IDUs often differ from those used in non-IDUs [4,5]. Some of these protocols may lead to inefficient and more costly care [6]. For instance, the current standard of care to rule out endocarditis and admit all IDUs who present to the ED with fever and an unclear source is a low-yield practice—rates of diagnosis of endocarditis in this population range from 3% to 20% [5,7]. A better understanding of the infectious illness presentations of IDUs may offer diagnostic clues and more efficient diagnostic evaluations [8]. For example, several investigators have noted possible associations between hyponatremia and serious bacterial infections in IDUs and have suggested that hyponatremia at the time of admission is a useful parameter in discriminating life-threatening necrotizing fasciitis [9-11]. Characterization of features of IDUs presentations may also provide useful information regarding risk assessment, allowing for the exploration of revision of admission criteria and improved resource utilization ⁎ Corresponding author at: Department of Emergency Medicine, San Francisco General Hospital, San Francisco, CA 94110. Tel.: +1 415 206 5875. E-mail address: [email protected] (R.M. Rodriguez). http://dx.doi.org/10.1016/j.ajem.2015.02.020 0735-6757/© 2015 Elsevier Inc. All rights reserved.
[12]. In this regard, we have developed a decision instrument and risk assessment tool for the prediction of endocarditis in febrile IDUs [13]. Our primary objective of this observational, descriptive (hypothesisgenerating) study was to characterize the ED presentations and hospital course of IDUs admitted to the hospital with serious infections. Specifically, we sought to contrast IDUs presenting clinical characteristics, laboratory data, culture results, complications, morbidity, and mortality with those of non-IDUs.
2. Methods 2.1. Study design and patient enrollment Before the study, we generated an inclusive list of infectious disease– related diagnoses (IDRD). At an urban, county level 1 trauma center from June 2010 to January 2011, we prospectively enrolled a consecutive sample of adult patients admitted to the hospital from the ED with any of these IDRD. We identified patients admitted with IDRD by reviewing daily ED admission logs. We excluded patients who, upon ED chart review, did not have an infection or suspected infection recorded in the ED final diagnosis section. We determined IDU vs non-IDU status by review of a required field on our ED electronic health record and review of history of present illness free text sections. Blank responses, which were less than 8% of
D.R. Kievlan et al. / American Journal of Emergency Medicine 33 (2015) 674–676 Table 1 Demographic data
Total Sex
Male Female Mean age (y) Ethnicity White African American Hispanic Asian/Pacific Islander Other Unknown Hospital length of stay (d) Hospital survival
675
Table 2 Discharge diagnoses IDU (% or IQR or SD)
Non-IDU (% or IQR or SD)
189 138 (73.0%) 51 (27.0%) 45 (34-51) 125 (66.1%) 46 (24.3%) 9 (4.8%) 5 (2.6%) 0 (0.0%) 4 (2.1%) 7.5 (10.3) 185 (97.9%)
408 255 (62.5%) 153 (37.5%) 50 (35-60) 124 (30.4%) 114 (27.9%) 83 (20.3%) 73 (17.9%) 10 (2.5%) 4 (1.0%) 6.1 (7.9) 396 (97.1%)
charts, were coded as non-IDU. Until we reached our a priori determined sample size of IDU subjects, we consecutively enrolled non-IDU subjects on a 2:1 basis.
2.2. Sample size determination Our sample size for this observational study was driven by determination of the width of 95% confidence intervals (CIs) around the point estimate of the proportion of patients expected to have hyponatremia. With prior studies showing rates of hyponatremia with serious infection ranging from 40% to 50% and a desired 95% CI width of 5%, we calculated that we would need to enroll approximately 170 patients in the IDU group.
2.3. Data collection, abstraction criteria, and outcome Using a structured abstraction tool and following the guidelines for chart abstraction set forth by Gilbert et al [14], we followed up enrolled subjects through their hospital stay and recorded the following patient characteristics, diagnostic testing results, and clinical outcomes including (1) demographic information (age, sex, ethnicity, housing status, and insurance); (2) medical history; (3) presence or absence of fever defined as temperature N 38.0°C at any time in the ED; (4) initial ED white blood cell counts, platelet counts, and serum sodium values; (5) microbiology culture results sent from the ED, including blood culture, wound culture, and urine culture results and antimicrobial sensitivities; (6) hospital course and survival to discharge; and (7) all ED admitting and hospital discharge diagnoses. In addition, for IDUs, we collected information regarding injection drugs of abuse, method of injection, and last reported injection of drugs. We stored data on Microsoft Excel (Microsoft Corp, Redmond, WA). To ensure interrater reliability, each reviewer reanalyzed 10% of the other's charts in a blinded fashion. The κ statistic from this analysis was 0.74 indicating good to excellent agreement.
1. 2. 3. 4.
IDU
Non-IDU
Cellulitis (n = 50, 26.5%) Pneumonia (n = 44, 23.3%) Abscess (n = 44, 23.3%) Bacteremia (n = 12, 6.3%)
Pneumonia (n = 98, 23.5%) Appendicitis (n = 64, 15.2%) Cellulitis (n = 51, 12.5%) Abscess (n = 43, 10.8%)
3. Results 3.1. We enrolled 603 subjects, of which 189 are IDUs, and 414 are non-IDUs Table 1 shows subject characteristics, and Table 2 shows the most common discharge diagnoses for IDUs and non-IDUs. Injection drug users were more commonly White and male. The ED and hospital discharge diagnoses were concordant in the vast majority of patients—95.8% of non-IDU patients and in 95.2% of IDU patients. Similar rates of fever in the ED were observed among IDUs (23.5%) and non-IDUs (24.7%). Injection drug users had higher rates of hyponatremia, 38.1% vs 27.1% (mean difference, 11.4% with 95% CI, 3.4%-19.6%) and thrombocytopenia, 18.5% vs 11.0% (mean difference, 7.5% with 95% CI, 1.5%-14.2%). Only 2 subjects from the IDU group and 5 from the non-IDU group had hyponatremia or thrombocytopenia as the primary admitting diagnoses. Leukocytosis was seen in fewer IDUs than non-IDUs, 36.0% vs 52.7% (mean difference, 16.7% with 95% CI, 8.2%-24.8%), with a difference correlating with higher rates of human immunodeficiency virus among IDUs, 32.3% vs 13.0% (mean difference, 19.8% with 95% CI, 12.6%-27.3%). Most IDU and non-IDU patients had blood cultures sent, and their overall rates of positive results from these cultures were similar (Table 3). Nine IDUs had blood cultures positive for methicillinresistant Staphylococcus aureus (MRSA); none of the non-IDUs had blood cultures positive for MRSA (Table 4). Fewer non-IDUs had wound cultures and urine cultures sent from the ED, but their yield positive for both of these was higher than the yields for IDUs. 4. Discussion We have contrasted features of infectious disease presentations of IDUs with those of non-IDUs in this prospectively enrolled cohort of patients admitted to the hospital from the ED. We also characterized and contrasted the most common admitting diagnoses for the 2 groups and found that IDUs more commonly had an admitting diagnosis of cellulitis. However, because we did not record data on all patients presenting to the ED with infections (we did not obtain data on those who were treated and discharged from the ED), we cannot determine whether IDUs had higher admission rates for cellulitis or other diagnoses. Injection drug users and non-IDUs had similar mortality and length of stay. The similar rates of hospital length of stay are notable. It is possible that early therapies in the ED, such as drainage of abscesses and antibiotics, may contribute to the similar length of stay among IDUs and non-IDUs.
Table 3 Culture results
2.4. Data analysis and statistical methodology We entered data into Microsoft Excel (Microsoft Corp, Seattle, WA). We calculated standard descriptive statistics (means, SDs, medians, interquartile ratios, and 95% CIs) using standard formulae in Microsoft Excel and STATA version 9.0 (STATA Corporation, College Station, TX). Demographic data were summarized and reported in aggregate form. Given prior studies suggesting possible differences in rates of hyponatremia, leukocytosis, and thrombocytopenia, we determined the mean difference and 95% CIs between IDUs and non-IDUs in these proportions.
Positive blood cx Positive wound cx Positive urine cx MRSA + in blood or wound cx MRSA + in blood cx
IDU
Non-IDU
Patients
Patients
With cx % sent
95% CI
with cx % sent
164 103 124 168
11.6%-22.9% 22.1%-39.5% 21.8%-37.6% 2.84%-9.87%
279 54 176 333
164
Abbreviation: cx, culture.
16.5% 30.1% 29.0% 5.4%
4.9% 2.91%-10.1% 279
95% CI
22.6% 18.1%-27.9% 77.8% 65.1%-86.8% 52.3% 44.9%-59.5% 0.3% 0.05%-1.2% 0.0%
0.0%-1.36%
676
D.R. Kievlan et al. / American Journal of Emergency Medicine 33 (2015) 674–676
Table 4 Pathogen data
Blood
Wound
Urine
IDU
Non-IDU
Pathogen
% Infected
% Infected
S coagulase negative MRSA S aureus E coli S aureus S coagulase negative Corynebacterium S viridans Gram-positive bacteria E coli Gram-negative bacteria
2.4% 4.9% 3.7% 0.0% 11.7% 2.9% 5.8% 7.8% 16.1% 8.9% 3.2%
8.2% 0.0% 3.2% 3.9% 40.7% 16.7% 16.7% 14.8% 24.4% 13.6% 4.5%
Abbreviations: S, Staphylococcus; E, Escherichia; MRSA, methicillin-resistant Staphylococcus aureus.
Although previous studies have retrospectively highlighted variances in presentations for IDU vs non-IDU differences for specific diagnoses (infective endocarditis), our research helps fill knowledge gaps regarding other general infection clinical presentations of IDUs vs non-IDUs. Notable findings in our study are the higher rates of hyponatremia and thrombocytopenia and lower rates of leukocytosis in IDUs. The pathophysiologic mechanisms underlying these differences are unclear. Hyponatremia and leukopenia have been reported in levamisole adulterated cocaine abusers—other similar drug toxicities may contribute to these findings [15,16]. Other investigators have noted that hyponatremia may be a clue to serious infection in IDUs [5,9-11]. We did not collect data on the severity of various admitting infections and therefore cannot comment as to whether the hyponatremia we noted is related to more severe illness. Regarding culture and antimicrobial data, we found that IDUs and non-IDUs had similar overall rates of pathogens grown in blood cultures, but only IDUs were positive for MRSA. This low yield of MRSA and its occurrence solely in IDU subjects are surprising considering recent literature describing widespread community-acquired MRSA [17,18]. The fact that IDUs had more wound and urine cultures sent with lower yields of pathogen growth may indicate selection bias toward increased testing in IDU patients, resulting from attempts to rule out endocarditis in this patient population. A strength of our study method is the prospective examination of a consecutive sample of patients with specific queries and information about their early (ED) presentation, which may offer more useful information to the emergency medicine practitioner than other retrospective studies that focused to a greater extent on their hospital course. Such data may lead to further development of decision guidelines and more focused assessments in the ED. 4.1. Limitations We conducted this study at a single, urban, county hospital that serves a large IDU population. Our findings may not reflect those with dissimilar patient populations. The primary data point of IDU status
was self-declared and therefore subject to multiple limitations of reporting bias, especially social desirability, in which subjects may have not wanted to admit their use of illicit drugs. 5. Conclusions In this cohort comparing infectious disease admissions of IDUs and non-IDUs, we found that IDUs more commonly presented with skin and soft tissue infections. Injection drug users had similar rates of fever, higher rates of hyponatremia and thrombocytopenia, and lower rates of leukocytosis in the ED. Although they had similar rates of bacteremia on ED-derived blood cultures, only IDUs were positive for MRSA. Injection drug users and non-IDUs had similar hospital length of stay and mortality. References [1] Lundgren L, Chassler D, Ben-Ami L, et al. Factors associated with emergency room use among injection drug users of African-American, Hispanic and WhiteEuropean background. Am J Addict 2005;14(3):268–80. [2] Chitwood DD, McBride DC, French MT, Comerford M. Health care need and utilization: a preliminary comparison of injection drug users, other illicit drug users, and nonusers. Subst Use Misuse 1999;34:727–46. [3] Chitwood DD, Sanchez J, Comerford M, McCoy CB. Primary preventive health care among injection drug users, other sustained drug users, and non-users. Subst Use Misuse 2001;36:807–24. [4] Gordon RJ, Lowy FD. Bacterial infections in drug users. NEJM 2005;353(18): 1945–54. [5] Brown PD, Levine DP. Infective endocarditis in the injection drug user. Infect Dis Clin N Am 2002;16:645–65. [6] Kerr T, Wood E, Grafstein E, et al. High rates of primary care and emergency department use among injection drug users in Vancouver. J Public Health (Oxf) 2005; 27(1):62–6. [7] Rodriguez RM, Alter H, Cisse B. Validation of a prediction rule for endocarditis in febrile injection drug users. Am J Emerg Med 2014;32(5):412–6. [8] Cisneros GO, Douaihy AB, Kirisci L. Access to healthcare among injection drug users at a needle exchange program in Pittsburgh, PA. J Addict Med 2009;3: 89–94. [9] Wall D, Kleain S, Black S, de Virgilio C. A simple model to help distinguish necrotizing from non-necrotizing soft-tissue infections. J Am Coll Surg 2000; 191(3):227–31. [10] Wong C, Khin L, Heng K, Tan K, Low C. The LRINEC (laboratory risk indicator for necrotising fasciitis) score: a tool for distinguishing necrotising fasciitis from other soft-tissue infections. Crit Care Med 2004;32:1535–41. [11] Yaghoubian A, de Virgilio C, Dauphine C, Lewis RJ, Lin M. Use of admission serum lactate and sodium levels to predict mortality in necrotizing soft-tissue infections. Arch Surg 2007;142:840–6. [12] Lonergan S, Rodriguez RM, Schaulis M, Navaran P. A case series of patients with black tar heroin-associated necrotizing fasciitis. J Emerg Med 2004; 26(1):47–50. [13] Chung-Esaki, Rodriguez RM, et al. Validation of a prediction rule for endocarditis in febrile injection drug users. Am J Emerg Med 2014;32:412–8. [14] Gilbert EH, Lowenstein SR, Koziol-McLain J, Barta DC, Steiner J. Chart reviews in emergency medicine research: where are the methods? Ann Emerg Med 1996; 27(3):305–8. [15] Magliocca KR, Coker NA, Parker SR. The head, neck, and systemic manifestations of levamisole-adulterated cocaine use. J Oral Maxillofac Surg 2013;71: 487–92. [16] Friend K, Milone MC, Perrone J. Hyponatremia associated with levamisoleadulterated cocaine use in emergency department patients. Ann Emerg Med 2012; 60:94–6. [17] Deleo FR, Otto M, Kreiswirth BN, Chambers HF. Community-associated methicillinresistant Staphylococcus aureus. Lancet 2010;375:1557–68. [18] Gardam MA. Is methicillin-resistant Staphylococcus aureus an emerging community pathogen? A review of the literature. Can J Infect Dis 2000;11:202–11.
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Original Contribution
Clinical profile of injection drug users presenting to the ED Daniel R. Kievlan, MD, Meri Gukasyan, BS, Julie Gesch, MD, Robert M. Rodriguez, MD ⁎ Department of Emergency Medicine, The University of California San Francisco, San Francisco, CA
a r t i c l e
i n f o
Article history: Received 1 December 2014 Received in revised form 10 February 2015 Accepted 10 February 2015
a b s t r a c t Background: Injection drug users (IDUs) commonly use the emergency department (ED) as their primary health care access point. Objective: We sought to characterize infectious disease clinical presentations and laboratory results of IDUs admitted to the hospital from the ED and contrast them with those of non-IDUs. Methods: We enrolled all admitted adult patients with infectious disease–related diagnoses at a county level 1 trauma center from June 2010 to January 2011 and used a structured chart abstraction tool to record patient characteristics and clinical outcomes. We compared clinical presenting features, laboratory data, and microbiological culture results of IDUs with concomitantly enrolled non-IDUs. Results: Of 603 total participants, 189 were IDUs, and 414 were non-IDUs. Injection drug users had higher rates of skin and soft tissue infection admission but had similar hospital length of stay (7.5 vs 6.1 days) and mortality (2.1% vs 2.9%). Compared with non-IDUs, IDUs more commonly had hyponatremia, 38.1% vs 27.1% (mean difference, 11.4%; 95% confidence intervals [CIs], 3.4%-19.6%) and thrombocytopenia, 18.5% vs 11.0% (mean difference, 7.5%; 95% CI, 1.5%-14.2%) but less frequently had leukocytosis, 36.0% vs 52.7% (mean difference, 16.7%; 95% CI, 8.2%-24.8%). Injection drug users and non-IDUs had similar rates of positive ED-derived blood cultures, 16.5% vs 22.6% (mean difference, 6.1%; 95% CI, −13.3 to 1.7%). Conclusions: When admitted from the ED for infectious disease–related diagnoses, IDUs had similar rates of fever, higher rates of hyponatremia and thrombocytopenia, and lower rates of leukocytosis than non-IDUs. Although they had similar rates of bacteremia, only IDUs were positive for methicillin-resistant Staphylococcus aureus. © 2015 Elsevier Inc. All rights reserved.
1. Introduction Injection drug users (IDUs), who are at significant risk for numerous serious, high morbidity and mortality infections, disproportionately use the emergency department (ED) for health care needs [1-3]. Because of greater risk for occult serious illness, current evaluation and management protocols for IDUs often differ from those used in non-IDUs [4,5]. Some of these protocols may lead to inefficient and more costly care [6]. For instance, the current standard of care to rule out endocarditis and admit all IDUs who present to the ED with fever and an unclear source is a low-yield practice—rates of diagnosis of endocarditis in this population range from 3% to 20% [5,7]. A better understanding of the infectious illness presentations of IDUs may offer diagnostic clues and more efficient diagnostic evaluations [8]. For example, several investigators have noted possible associations between hyponatremia and serious bacterial infections in IDUs and have suggested that hyponatremia at the time of admission is a useful parameter in discriminating life-threatening necrotizing fasciitis [9-11]. Characterization of features of IDUs presentations may also provide useful information regarding risk assessment, allowing for the exploration of revision of admission criteria and improved resource utilization ⁎ Corresponding author at: Department of Emergency Medicine, San Francisco General Hospital, San Francisco, CA 94110. Tel.: +1 415 206 5875. E-mail address: [email protected] (R.M. Rodriguez). http://dx.doi.org/10.1016/j.ajem.2015.02.020 0735-6757/© 2015 Elsevier Inc. All rights reserved.
[12]. In this regard, we have developed a decision instrument and risk assessment tool for the prediction of endocarditis in febrile IDUs [13]. Our primary objective of this observational, descriptive (hypothesisgenerating) study was to characterize the ED presentations and hospital course of IDUs admitted to the hospital with serious infections. Specifically, we sought to contrast IDUs presenting clinical characteristics, laboratory data, culture results, complications, morbidity, and mortality with those of non-IDUs.
2. Methods 2.1. Study design and patient enrollment Before the study, we generated an inclusive list of infectious disease– related diagnoses (IDRD). At an urban, county level 1 trauma center from June 2010 to January 2011, we prospectively enrolled a consecutive sample of adult patients admitted to the hospital from the ED with any of these IDRD. We identified patients admitted with IDRD by reviewing daily ED admission logs. We excluded patients who, upon ED chart review, did not have an infection or suspected infection recorded in the ED final diagnosis section. We determined IDU vs non-IDU status by review of a required field on our ED electronic health record and review of history of present illness free text sections. Blank responses, which were less than 8% of
D.R. Kievlan et al. / American Journal of Emergency Medicine 33 (2015) 674–676 Table 1 Demographic data
Total Sex
Male Female Mean age (y) Ethnicity White African American Hispanic Asian/Pacific Islander Other Unknown Hospital length of stay (d) Hospital survival
675
Table 2 Discharge diagnoses IDU (% or IQR or SD)
Non-IDU (% or IQR or SD)
189 138 (73.0%) 51 (27.0%) 45 (34-51) 125 (66.1%) 46 (24.3%) 9 (4.8%) 5 (2.6%) 0 (0.0%) 4 (2.1%) 7.5 (10.3) 185 (97.9%)
408 255 (62.5%) 153 (37.5%) 50 (35-60) 124 (30.4%) 114 (27.9%) 83 (20.3%) 73 (17.9%) 10 (2.5%) 4 (1.0%) 6.1 (7.9) 396 (97.1%)
charts, were coded as non-IDU. Until we reached our a priori determined sample size of IDU subjects, we consecutively enrolled non-IDU subjects on a 2:1 basis.
2.2. Sample size determination Our sample size for this observational study was driven by determination of the width of 95% confidence intervals (CIs) around the point estimate of the proportion of patients expected to have hyponatremia. With prior studies showing rates of hyponatremia with serious infection ranging from 40% to 50% and a desired 95% CI width of 5%, we calculated that we would need to enroll approximately 170 patients in the IDU group.
2.3. Data collection, abstraction criteria, and outcome Using a structured abstraction tool and following the guidelines for chart abstraction set forth by Gilbert et al [14], we followed up enrolled subjects through their hospital stay and recorded the following patient characteristics, diagnostic testing results, and clinical outcomes including (1) demographic information (age, sex, ethnicity, housing status, and insurance); (2) medical history; (3) presence or absence of fever defined as temperature N 38.0°C at any time in the ED; (4) initial ED white blood cell counts, platelet counts, and serum sodium values; (5) microbiology culture results sent from the ED, including blood culture, wound culture, and urine culture results and antimicrobial sensitivities; (6) hospital course and survival to discharge; and (7) all ED admitting and hospital discharge diagnoses. In addition, for IDUs, we collected information regarding injection drugs of abuse, method of injection, and last reported injection of drugs. We stored data on Microsoft Excel (Microsoft Corp, Redmond, WA). To ensure interrater reliability, each reviewer reanalyzed 10% of the other's charts in a blinded fashion. The κ statistic from this analysis was 0.74 indicating good to excellent agreement.
1. 2. 3. 4.
IDU
Non-IDU
Cellulitis (n = 50, 26.5%) Pneumonia (n = 44, 23.3%) Abscess (n = 44, 23.3%) Bacteremia (n = 12, 6.3%)
Pneumonia (n = 98, 23.5%) Appendicitis (n = 64, 15.2%) Cellulitis (n = 51, 12.5%) Abscess (n = 43, 10.8%)
3. Results 3.1. We enrolled 603 subjects, of which 189 are IDUs, and 414 are non-IDUs Table 1 shows subject characteristics, and Table 2 shows the most common discharge diagnoses for IDUs and non-IDUs. Injection drug users were more commonly White and male. The ED and hospital discharge diagnoses were concordant in the vast majority of patients—95.8% of non-IDU patients and in 95.2% of IDU patients. Similar rates of fever in the ED were observed among IDUs (23.5%) and non-IDUs (24.7%). Injection drug users had higher rates of hyponatremia, 38.1% vs 27.1% (mean difference, 11.4% with 95% CI, 3.4%-19.6%) and thrombocytopenia, 18.5% vs 11.0% (mean difference, 7.5% with 95% CI, 1.5%-14.2%). Only 2 subjects from the IDU group and 5 from the non-IDU group had hyponatremia or thrombocytopenia as the primary admitting diagnoses. Leukocytosis was seen in fewer IDUs than non-IDUs, 36.0% vs 52.7% (mean difference, 16.7% with 95% CI, 8.2%-24.8%), with a difference correlating with higher rates of human immunodeficiency virus among IDUs, 32.3% vs 13.0% (mean difference, 19.8% with 95% CI, 12.6%-27.3%). Most IDU and non-IDU patients had blood cultures sent, and their overall rates of positive results from these cultures were similar (Table 3). Nine IDUs had blood cultures positive for methicillinresistant Staphylococcus aureus (MRSA); none of the non-IDUs had blood cultures positive for MRSA (Table 4). Fewer non-IDUs had wound cultures and urine cultures sent from the ED, but their yield positive for both of these was higher than the yields for IDUs. 4. Discussion We have contrasted features of infectious disease presentations of IDUs with those of non-IDUs in this prospectively enrolled cohort of patients admitted to the hospital from the ED. We also characterized and contrasted the most common admitting diagnoses for the 2 groups and found that IDUs more commonly had an admitting diagnosis of cellulitis. However, because we did not record data on all patients presenting to the ED with infections (we did not obtain data on those who were treated and discharged from the ED), we cannot determine whether IDUs had higher admission rates for cellulitis or other diagnoses. Injection drug users and non-IDUs had similar mortality and length of stay. The similar rates of hospital length of stay are notable. It is possible that early therapies in the ED, such as drainage of abscesses and antibiotics, may contribute to the similar length of stay among IDUs and non-IDUs.
Table 3 Culture results
2.4. Data analysis and statistical methodology We entered data into Microsoft Excel (Microsoft Corp, Seattle, WA). We calculated standard descriptive statistics (means, SDs, medians, interquartile ratios, and 95% CIs) using standard formulae in Microsoft Excel and STATA version 9.0 (STATA Corporation, College Station, TX). Demographic data were summarized and reported in aggregate form. Given prior studies suggesting possible differences in rates of hyponatremia, leukocytosis, and thrombocytopenia, we determined the mean difference and 95% CIs between IDUs and non-IDUs in these proportions.
Positive blood cx Positive wound cx Positive urine cx MRSA + in blood or wound cx MRSA + in blood cx
IDU
Non-IDU
Patients
Patients
With cx % sent
95% CI
with cx % sent
164 103 124 168
11.6%-22.9% 22.1%-39.5% 21.8%-37.6% 2.84%-9.87%
279 54 176 333
164
Abbreviation: cx, culture.
16.5% 30.1% 29.0% 5.4%
4.9% 2.91%-10.1% 279
95% CI
22.6% 18.1%-27.9% 77.8% 65.1%-86.8% 52.3% 44.9%-59.5% 0.3% 0.05%-1.2% 0.0%
0.0%-1.36%
676
D.R. Kievlan et al. / American Journal of Emergency Medicine 33 (2015) 674–676
Table 4 Pathogen data
Blood
Wound
Urine
IDU
Non-IDU
Pathogen
% Infected
% Infected
S coagulase negative MRSA S aureus E coli S aureus S coagulase negative Corynebacterium S viridans Gram-positive bacteria E coli Gram-negative bacteria
2.4% 4.9% 3.7% 0.0% 11.7% 2.9% 5.8% 7.8% 16.1% 8.9% 3.2%
8.2% 0.0% 3.2% 3.9% 40.7% 16.7% 16.7% 14.8% 24.4% 13.6% 4.5%
Abbreviations: S, Staphylococcus; E, Escherichia; MRSA, methicillin-resistant Staphylococcus aureus.
Although previous studies have retrospectively highlighted variances in presentations for IDU vs non-IDU differences for specific diagnoses (infective endocarditis), our research helps fill knowledge gaps regarding other general infection clinical presentations of IDUs vs non-IDUs. Notable findings in our study are the higher rates of hyponatremia and thrombocytopenia and lower rates of leukocytosis in IDUs. The pathophysiologic mechanisms underlying these differences are unclear. Hyponatremia and leukopenia have been reported in levamisole adulterated cocaine abusers—other similar drug toxicities may contribute to these findings [15,16]. Other investigators have noted that hyponatremia may be a clue to serious infection in IDUs [5,9-11]. We did not collect data on the severity of various admitting infections and therefore cannot comment as to whether the hyponatremia we noted is related to more severe illness. Regarding culture and antimicrobial data, we found that IDUs and non-IDUs had similar overall rates of pathogens grown in blood cultures, but only IDUs were positive for MRSA. This low yield of MRSA and its occurrence solely in IDU subjects are surprising considering recent literature describing widespread community-acquired MRSA [17,18]. The fact that IDUs had more wound and urine cultures sent with lower yields of pathogen growth may indicate selection bias toward increased testing in IDU patients, resulting from attempts to rule out endocarditis in this patient population. A strength of our study method is the prospective examination of a consecutive sample of patients with specific queries and information about their early (ED) presentation, which may offer more useful information to the emergency medicine practitioner than other retrospective studies that focused to a greater extent on their hospital course. Such data may lead to further development of decision guidelines and more focused assessments in the ED. 4.1. Limitations We conducted this study at a single, urban, county hospital that serves a large IDU population. Our findings may not reflect those with dissimilar patient populations. The primary data point of IDU status
was self-declared and therefore subject to multiple limitations of reporting bias, especially social desirability, in which subjects may have not wanted to admit their use of illicit drugs. 5. Conclusions In this cohort comparing infectious disease admissions of IDUs and non-IDUs, we found that IDUs more commonly presented with skin and soft tissue infections. Injection drug users had similar rates of fever, higher rates of hyponatremia and thrombocytopenia, and lower rates of leukocytosis in the ED. Although they had similar rates of bacteremia on ED-derived blood cultures, only IDUs were positive for MRSA. Injection drug users and non-IDUs had similar hospital length of stay and mortality. References [1] Lundgren L, Chassler D, Ben-Ami L, et al. Factors associated with emergency room use among injection drug users of African-American, Hispanic and WhiteEuropean background. Am J Addict 2005;14(3):268–80. [2] Chitwood DD, McBride DC, French MT, Comerford M. Health care need and utilization: a preliminary comparison of injection drug users, other illicit drug users, and nonusers. Subst Use Misuse 1999;34:727–46. [3] Chitwood DD, Sanchez J, Comerford M, McCoy CB. Primary preventive health care among injection drug users, other sustained drug users, and non-users. Subst Use Misuse 2001;36:807–24. [4] Gordon RJ, Lowy FD. Bacterial infections in drug users. NEJM 2005;353(18): 1945–54. [5] Brown PD, Levine DP. Infective endocarditis in the injection drug user. Infect Dis Clin N Am 2002;16:645–65. [6] Kerr T, Wood E, Grafstein E, et al. High rates of primary care and emergency department use among injection drug users in Vancouver. J Public Health (Oxf) 2005; 27(1):62–6. [7] Rodriguez RM, Alter H, Cisse B. Validation of a prediction rule for endocarditis in febrile injection drug users. Am J Emerg Med 2014;32(5):412–6. [8] Cisneros GO, Douaihy AB, Kirisci L. Access to healthcare among injection drug users at a needle exchange program in Pittsburgh, PA. J Addict Med 2009;3: 89–94. [9] Wall D, Kleain S, Black S, de Virgilio C. A simple model to help distinguish necrotizing from non-necrotizing soft-tissue infections. J Am Coll Surg 2000; 191(3):227–31. [10] Wong C, Khin L, Heng K, Tan K, Low C. The LRINEC (laboratory risk indicator for necrotising fasciitis) score: a tool for distinguishing necrotising fasciitis from other soft-tissue infections. Crit Care Med 2004;32:1535–41. [11] Yaghoubian A, de Virgilio C, Dauphine C, Lewis RJ, Lin M. Use of admission serum lactate and sodium levels to predict mortality in necrotizing soft-tissue infections. Arch Surg 2007;142:840–6. [12] Lonergan S, Rodriguez RM, Schaulis M, Navaran P. A case series of patients with black tar heroin-associated necrotizing fasciitis. J Emerg Med 2004; 26(1):47–50. [13] Chung-Esaki, Rodriguez RM, et al. Validation of a prediction rule for endocarditis in febrile injection drug users. Am J Emerg Med 2014;32:412–8. [14] Gilbert EH, Lowenstein SR, Koziol-McLain J, Barta DC, Steiner J. Chart reviews in emergency medicine research: where are the methods? Ann Emerg Med 1996; 27(3):305–8. [15] Magliocca KR, Coker NA, Parker SR. The head, neck, and systemic manifestations of levamisole-adulterated cocaine use. J Oral Maxillofac Surg 2013;71: 487–92. [16] Friend K, Milone MC, Perrone J. Hyponatremia associated with levamisoleadulterated cocaine use in emergency department patients. Ann Emerg Med 2012; 60:94–6. [17] Deleo FR, Otto M, Kreiswirth BN, Chambers HF. Community-associated methicillinresistant Staphylococcus aureus. Lancet 2010;375:1557–68. [18] Gardam MA. Is methicillin-resistant Staphylococcus aureus an emerging community pathogen? A review of the literature. Can J Infect Dis 2000;11:202–11.
