Original Contribution

National epidemiology of Cutaneous abscesses: 1996 to 2005

Breena R. Taira MD?, Adam J. Singer MD, Henry C. Thode Jr PhD, Christopher C. Lee MD

Department of Emergency Medicine, Stony Brook University Medical Center, Stony Brook, New York

Received 20 December 2007; revised 1 February 2008; accepted 15 February 2008

Abstract

Objective: Little has been reported regarding the national epidemiology of cutaneous abscesses. We examined the National Hospital Ambulatory Medical Care Survey national estimates of all emergency department (ED) visits from 1996 to 2005 to determine the trend and the epidemiology of ED abscess visits.

Methods: Study design: retrospective analysis of NHAMCS databases for 1996 to 2005 available from the National Center for Health Statistics. Subjects: all patients with a first diagnosis of abscess based on the International Classification of Diseases, Ninth Revision, Clinical Modification, Diagnosis codes were selected for analysis. Measures: estimated total numbers and percentages of patients by year. Analysis: trends from 1996 through 2005 were examined overall and by demographic factors (eg, age, sex) and Abscess characteristics (eg, body region affected). Linear regression was used to evaluate trends. Results: Emergency department visits for abscesses more than doubled over the 10-year study period (1.2 million in 1996 to 3.28 million in 2005; trend, P b .01). The total number of ED visits increased from 90 million to 115 million over the same period, so that abscess visits are increasing faster than overall visits. Although the frequency of abscesses increased, the demographic and clinical characteristics of ED patients were unchanged over time. About half of ED patients with abscess were male, and about half were between the ages of 19 and 45 years. Annual admissions hovered around 12%. The most common abscess sites coded were the leg, ear, and “unspecified site.” About 50% received antibiotics.

Conclusions: Emergency department visits for abscesses have shown a large increase since 1996; however, Demographic and clinical factors are uniform across years.

(C) 2009

Introduction

According to a 2007 report from the National Center for Health Statistics, infections of the skin are the seventh most common reason for emergency department (ED) visits, with nearly 2.7 million visits (2.3%) to the ED in 2005 because of

Presented in part at the 2007 SAEM NY Regional Conference, New York, NY, March 28, 2007.

* Corresponding author.

cellulitis and abscesses [1]. Despite the large number of cutaneous abscesses, there are very little data regarding its national epidemiology. A study from 1977 from the University of Chicago and Hospitals, Chicago, Ill, estimated that 2% of all patient visits to the adult ED were for treatment of such abscesses [2]. Since then, most studies have focused on the distribution and microbiology of abscesses. Further- more, there have been very few multicenter studies describing the demographic and clinical characteristics of patients with abscesses [3].

0735-6757/$ – see front matter (C) 2009 doi:10.1016/j.ajem.2008.02.027

290 B.R. Taira et al.

For the last few years, there has been a gradual change in the microbiology of cutaneous abscesses. Methicillin- resistant Staphylococcus aureus (MRSA) is now the most common cause of cutaneous abscesses in the United States [3]. Recently, several reports also describe a rise in community-acquired MRSA (CAMRSA). Community- acquired MRSA skin infections have been described as “an emerging epidemic” [4]. Frazee et al [5] found an association between furuncles or superficial skin abscess and MRSA. Furthermore, Cohen [6] showed that the incidence of cutaneous abscesses caused by CAMRSA infection is increasing. With the recent increase in the number of ED visits and the growing interest in the emerging pathogens causing abscesses, we thought that it was timely to explore the nationwide epidemiology of cutaneous abscesses using a large database.

Methods

Study design

In the current study, we analyzed the ED component of the 1996 to 2005 National Hospital Ambulatory Medical Care Survey [7]. The study was exempt from review by our institutional review board.

Study setting and population

Briefly, NHAMCS encompasses a national probability sample of visits to US hospital emergency and outpatient departments by the Division of Health Care Statistics of the National Center for Health Statistics, Centers for Disease Control and Prevention; only the ED data were used in these analyses. The survey uses a 4-stage sampling design, covering geographic primary sampling units, hospitals within primary sampling units, EDs within hospitals, and patient visits within EDs. Hospitals are stratified by region, presence of ED, ownership type, and size. Within each stratum, hospitals are selected with a probability proportional to the number of ED visits. Patient visits are systematically selected over a randomly assigned 4-week period. For EDs with more than 200 visits during the 4-week period, visits are sampled with a systematic procedure by selecting every nth sequential visit after a random start.

Study protocol

Visit sampling and data collection were recorded on patient record forms by hospital staff or by field representa- tives from the US Bureau of Census. Data collection methods do not indicate that data recording by hospital staff was done prospectively; data recording by field representatives was performed as a medical chart review. Therefore, this study should be considered (conservatively) as a retrospective

Fig. 1 total ED visits for abscesses by year 1996 to 2005.

chart review. Data processing and coding were performed by an external source.

We identified a cutaneous abscess by the International Classification of Diseases, Ninth Revision, Clinical Modifica- tion, diagnosis codes in the primary diagnosis field. These codes include head/neck abscesses: 382, 373.13, 380.1, 386.3, 526.4, 528.5, 682, 682.1, 682.8; trunk abscesses: 510.9, 566,

611, 682.2, 682.5, 607.2, 608.4, 616.3, 616.4; upper extremity

abscesses: 682.3, 682.4, 681, 681.02; lower extremity

abscesses: 682.6, 682.7, 681.1, 681.11; and abscesses of unspecified location: 682.9, 685, 998.59. In terms of antibiotic use, over the 9 annual surveys, between 6 (1996-2002) and 8 (2003-2005) medications were recorded per encounter; all recorded medications were considered in the analyses. Up to 3 National Drug Class codes were provided for each medi- cation [8]. Antibiotic use was identified on the basis of any of the following drug class codes: penicillins, cephalosporins, lincosamides or macrolides, polymyxins, tetracyclines, chlor- amphenicol or derivatives, aminoglycosides, sulfonamides or related compounds, antibacterials miscellaneous, or quino- lones or derivatives.

Data analysis

Population visits and visit rates were computed by using the population weights used by NHAMCS to calculate national estimates of the number of ED visits. Estimates included the number of visits and the percentage of visits with antibiotics. Confidence intervals were calculated for percentages using SEs, which were estimated using the methods described by NHAMCS survey documentation. Trends were computed across all years using weighted linear regression to account for the sampling scheme used in the NHAMCS survey; weights were the inverse of the variance estimates calculated from the SEs. Analyses were performed using SPSS for Windows 13.0 (SPSS Inc, Chicago, Ill).

Epidemiology of abscesses 291

Fig. 2 Distribution of abscess visits by age, 2005.

Trends from 1996 through 2005 were examined overall and by demographic factors (eg, age, sex) and abscess character- istics (eg, body region affected).

Results

Emergency department visits for abscesses more than doubled over the 10-year study period (1.2 million in 1996 to 3.28 million in 2005; trend, P b .01; Fig. 1). The total number of ED visits increased from 90 million to 115.3 million over the same period, so that abscess visits are increasing faster than the overall rate of visits. Although the frequency of abscesses increased, the demographic and clinical characteristics of ED patients were unchanged over time. The region of the United States with the highest number of patients presenting with abscesses was the South. About half of the ED patients with abscess were male, and about half were between the ages of 19 and 45 years (Fig. 2). Annual admissions hovered around 12%. The most common abscess sites coded were to the leg, ear, and “unspecified site” (Fig. 3). About 50% of patients with abscess received antibiotics.

For the year 2005, we analyzed the temperature, heart rate, and blood pressure of patients with abscesses to evaluate the proportion of patients with abscess with signs of Systemic Infection. Of the 3,283,549 visits for abscesses, 2.9% had a fever of 101.3?F or higher; however, 6.1% had a fever if the definition was 100.4?F or higher. A heart rate of 100 or greater was found in 25.9%. Median (interquartile range) blood pressures were 131 (116-145) systolic and 76 (69-85) diastolic.

Discussion

Our study demonstrates a disproportionate rise in the number of cutaneous abscesses over the study period.

Although ED visits increased by 30% between 1996 and 2005, the number of abscesses more than doubled. There are several possible reasons why the number of abscesses has grown to such an extent. First, it is possible that the incidence of new cases is on the rise. This may be caused by new emerging pathogens such as MRSA and CAMRSA or an increase in the risk factors such as close contact and hot, humid conditions. With the large number of uninsured in this country, it is also possible that more patients with abscesses are presenting to the ED instead of to their primary care physician. Finally, there also may have been a gradual trend in the way soft tissue infections are coded.

Although visits for other types of cutaneous injury to EDs have been on the decline, we found an increase in the number of visits for cutaneous abscesses for the last 10 years. This is faster than the increase in overall visits to EDs over the same period. Methicillin-resistant S. aureus is the most common cause of cutaneous abscess in the United States [3]. Frazee et al [5], in their 2005 investigation of skin and soft tissue infections presenting to an ED, found that 49.6% of patients were infected with MRSA, and that of those with MRSA infection, 76% fit the clinical definition of CAMRSA. They further reported a strong association between furunculosis and community-associated MRSA. The presence of a furuncle was a predictor variable independently associated with both MRSA colonization (odds ratio, 5) and with MRSA infection (odds ratio, 28.6).

Community-acquired MRSA skin infections have been described as “an emerging epidemic” [4]. Community- acquired MRSA tends to be resistant to fewer antibiotics, produces a different set of toxins, and has a different gene complex than MRSA [3]. Associated risk factors that are known for MRSA are not necessarily present in patients with CAMRSA infection. This increase in the prevalence of CAMRSA may well be responsible for the increased numbers of patients presenting to the ED for cutaneous

Fig. 3 Distribution of abscess visits by body region, 2005.

292 B.R. Taira et al.

abscess. Further studies are necessary to investigate a possible relationship between the rise in CAMRSA and the increased incidence of abscesses.

In addition, we assessed several characteristics of the patients included such as age. The 19- to 45-year age group had the highest incidence of cutaneous abscesses. Interest- ingly, the number of MRSA infections were the same across all age groups in the multivariate analysis performed by Frazee [5]. Furthermore, we characterized the location of abscess and found that the most common sites were leg, ear, and other “unspecified site.” The most common locations of abscess on the body in the Moran study were the extremities with upper and lower extremities approximately equal, followed by torso, perineum, and, finally, head and neck [3]. The Southern United States had a slightly higher percentage of visits for abscess when compared with other regions. Although CAMRSA outbreaks have been reported from 31 states, humid environment has been postulated to contribute to increased transmission of CAMRSA [9]. Humidity is a possible explanation for the increased occurrence of abscesses in the southern United States. Overall, these demographic and clinical factors remain unchanged over the 9-year study period.

Finally, we evaluated antibiotic use in EDs for these cutaneous abscesses and found that 50% of the patients in this study were prescribed antibiotics for their abscess. Even before the upsurge in CAMRSA prevalence, controversy existed about the value of antibiotic therapy after successful incision and drainage of cutaneous abscesses. A double- blind study of 50 patients randomized to cephradine (n = 27) or placebo (n = 23) demonstrated no benefit of oral antibiotics after 1 week [10]. Community-acquired MRSA, however, has changed the discussion of antibiotic selection in the ED for skin infection and questions whether standard practice for these types of infections is enough treatment [11]. Community-acquired MRSA skin and soft tissue infections have been observed to persist, worsen, and/or recur despite incision and drainage, especially when patients are not given antibiotic or given an antibiotic to which the bacterium is resistant [9]. Some reports have, therefore, recommended that a Bacterial culture routinely be obtained from the wound at the initial visit [3,9]. As the incidence of CAMRSA continues to climb, previously popular antimi- crobials for skin and soft tissue infection such as cephalexin and dicloxacillin will be inadequate for increasing numbers of patients. It may be more appropriate to use oral agents such as clindamycin, trimethoprim-sulfamethoxazole, and rifampin [3,12]. An additional consideration in terms of antimicrobial therapy is that elimination of nasal carriage is reported to reduce the likelihood of recurrent abscesses [13]. Our study has several limitations. They include the study design as a secondary analysis of large database. Further- more, because the NHAMCS is a large administrative

database, the training of the abstractors is uncertain. Finally, lack of additional information may confound results.

Conclusions

Emergency department visits for abscesses have shown a large increase since 1996; however, demographic and clinical factors remain uniform across years. This may be secondary to the increasing prevalence of CAMRSA. This infection should be considered when encountering any patient with skin or soft tissue infection in the ED. Further studies are necessary to elucidate the treatment algorithm best suited to prevent and treat recurrences of cutaneous abscess.

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