The incidence of skin and soft tissue infections (SSTI) in the general population has been increasing in recent years, resulting in a larger number of patients being seen and treated in the Emergency Department (ED), as well as admitted to the hospital [
Despite the increase in ED SSTI presentations, treatment recommendations remain predominantly nonspecific concerning antibiotic choice and need for admission. The most recent Infectious Diseases Society of America (IDSA) guidelines from 2014 sought to classify patients into mild, moderate, or severe infections, but allow for provider interpretation of systemic signs of illness [
Given the morbidity, mortality, and cost associated with the increasing SSTI prevalence in the ED, particularly resulting from initial treatment failure, it is clearly important to delineate features associated with more serious disease [
The study was performed prospectively at a large, urban, county hospital ED with an annual census of more than 100,000 visits. The ED is staffed by practicing emergency physicians, emergency medicine residents, and advanced practice providers 24 hours daily, seven days per week. The study was reviewed and approved by our institutions’ Internal Review Board.
Patients were prospectively enrolled from a convenience sample of adults aged 18 or older presenting to the ED with a chief complaint of skin and soft tissue infection (SSTI) including cellulitis, abscess, abscess with cellulitis, carbuncle, and furuncles, over a nine-month period including 2016-17, between the hours of 0800 and 1700. Participant identification and confirmation of eligibility were evaluated through the review of electronic medical records (EMR). Inclusion criteria were defined as age 18 or older, SSTI as the chief complaint, and access to a telephone. Exclusion criteria included diagnosis of gangrene, diagnosis of necrotizing fasciitis, diagnosis of diabetic foot ulcer(s), diagnosis of osteomyelitis, diagnosis of septic arthritis, diagnosis of decubitus ulcer(s), current pregnancy, patient status as a prisoner, and presentation with chief complaint other than SSTI. These diagnoses were excluded if present at the time of ED presentation only. Patients were presented with the details of the study and enrolled after obtaining informed consent.
Vital signs were collected in triage upon admission to the ED. The following data were collected from each patient: demographics; assessment of obesity (defined as BMI ≥ 30); smoking status; alcohol consumption; current IV drug use (IVDU); history of diabetes mellitus, connective tissue disease, liver disease, cancer, renal disease, hidradenitis, chronic edema, venous insufficiency, and chronic leg ulcers/wounds; human bite exposure; mammal bite exposure; antibiotic exposure in the past month for any reason; history of SSTI in the past year; abscess incision and drainage in the past year; and history of surgery in the area of infection.
The maximal area of erythema of the SSTI was measured and assigned to one of the following bodily areas: head, torso, arm, hand, leg, foot, or multiple site. All measurements were performed by a single investigator (NB). If performed, incision and drainage of the SSTI were recorded. Relevant laboratory data obtained throughout the visit were also collected via EMR, including WBC count, ESR, and CRP. Antibiotics administered during the visit, prescribed at discharge, and/or administered during admission were recorded and differentiated by route of administration and specific antibiotic.
The treating physician or provider was then questioned for their patient’s final diagnosis: cellulitis, abscess, or abscess with surrounding cellulitis. Each physician or provider was then presented with a survey asking them to identify their intended disposition of the patient (discharge home, admission to the observation unit, admission to the floor, admission to medical step-down, or admission to the intensive care unit) and identify which of the following factors influenced their disposition decision: SSTI area, SSTI location, presence of comorbidities, absence of comorbidities, systemic illness, absence of systemic illness, immunosuppression, or failure of prior treatment. Respondents were then free to provide any additional rationale. If the patient was not discharged home, the provider was asked to provide an anticipated length of stay (LOS).
Each patient was contacted by phone two weeks following their discharge from the index visit to the ED. Patients were contacted three different days by phone for follow-up questions. If we were not able to reach them by phone then medical records were evaluated to determine if a return visit took place. Return visit(s) to an ED for the same infection, changes in discharge antibiotics, and readmission if originally admitted were recorded. Review of the EMR was conducted for those patients admitted to any area of the hospital to document LOS, any changes in antibiotics, and discharge destination: home, skilled nursing facility (SNF), rehabilitation/long-term acute care (LTAC), hospice care, or morgue.
The primary outcomes of the study were the initial disposition of the patient following ED presentation and treatment failure, defined as repeat ED visit for the same SSTI, an antibiotic change within the 2-week follow-up period, readmission to the hospital, or any combination of these factors. Secondary outcomes included LOS, provider reasoning, and anticipated LOS.
All data were entered into a database for analysis and analyzed using Stata 13.0 (StataCorp, LLC, College Station, TX, USA) and MiniTab Express 1.5 (MiniTab Inc., State College, PA, USA). Data are reported as frequencies and medians with interquartile ranges (IQR). Comparisons of groups were performed using the
Demographic and patient characteristics thought to be clinically relevant to disposition decision on descriptive evaluation of the database were evaluated by simple binary logistic regression for assessment of univariate significance. Insignificant characteristics (p < 0.25) were excluded and the following were entered into a logistic regression controlled for age and gender: IVDU, diabetes mellitus, chronic edema, venous insufficiency, chronic leg ulcers, antibiotic use within the past month, and recent surgery at the site of infection. The effects of location of infection on disposition and diagnosis on disposition were also explored via independent logistic regressions, both controlled for age and gender.
Demographic and patient characteristics thought to be relevant to treatment failure (p > 0.25) also underwent univariate analysis, with the following significant variables being placed into a logistic regression controlled for age and gender: antibiotic within the past month, recent surgery in the area of infection, and chronic leg ulcers. Individual logistic regressions were also performed to determine the effect of infection site, diagnosis, antibiotic administration route, and disposition on treatment failure which were reported as odds ratios (OR). All were controlled for age and area of infection.
125 patients were initially enrolled in the study and there were no subsequent exclusions. Median age was 39 years (interquartile range [IQR]: 31-56 years). Males comprised 69 (55.2%) of patients. Ten participants (8.0%) were identified as IV drug users. The most commonly reported comorbidity was chronic edema in 30 patients (24.0%). Also reported were 16 (12.8%) patients with diabetes mellitus, 10 (8.0%) with liver disease, 14 (11.2%) with venous insufficiency, and 7 (5.6%) with chronic leg ulcers. Forty patients (32.0%) had received antibiotics within the month prior to presentation, 50 (40.0 %) reported a SSTI within a year prior to presentation, and 18 (14.4%) had recent surgery in infection. Other demographic data and participant characteristics are shown in Table
Demographic data and characteristics of enrolled patients.
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Age (years; median [IQR]) | 39.0 [31.0, 56.0] | 58.0 [36.5, 67.8] |
Gender - n (%) | ||
Male | 69 (55.2) | 18 (56.3) |
Obese - n (%) | 39 (31.2) | 7 (21.9) |
Smoking - n (%) | 72 (57.6) | 17 (53.1) |
>15 Alcoholic Drinks per Week - n (%) | 9 (7.2) | 1 (3.1) |
IV Drug Use - n (%) | 10 (8.0) | 5 (15.6) |
Comorbidities - n (%) | ||
Diabetes Mellitus | 16 (12.8) | 9 (28.1) |
Liver Disease | 10 (8.0) | 4 (12.5) |
Active Cancer | 2 (1.6) | 1 (3.1) |
Renal Disease | 3 (2.4) | 2 (6.3) |
Hidradenitis | 5 (4.0) | 1 (3.1) |
Chronic Edema | 30 (24.0) | 15 (46.9) |
Venous Insufficiency | 14 (11.2) | 9 (28.1) |
Chronic Leg Ulcers/Wounds | 7 (5.6) | 5 (15.6) |
Human Bite - n (%) | 0 (0.0) | 0 (0.0) |
Mammal Bite - n (%) | 6 ( 4.8) | 2 (6.3) |
Antibiotics in the Past 4 Weeks - n (%) | 40 (32.0) | 16 (50.0) |
SSTI in the Past Year - n (%) | 50 (40.0) | 15 (46.9) |
Abscess Drainage in the Past Year - n (%) | 27 (21.6) | 6 (18.8) |
Prior Surgery in Area of SSTI - n (%) | 18 (14.4) | 9 (28.1) |
Clinical characteristics of enrolled patients.
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Vitals (median [IQR]) | ||
Temperature (C) | 36.8 [36.6, 36.9] | 36.8 [36.6, 37.0] |
Systolic Blood Pressure (mmHg) | 135.0 [123.0, 145.0] | 139.0 [127.3, 152.3] |
Diastolic Blood Pressure (mmHg) | 79.0 [70.0, 86.0] | 79.0 [67.8, 88.5] |
Heart Rate (1/min) | 83 |
81 |
Oxygen Saturation (%) | 98.0 [97.0, 99.0] | 97.5 [96.0, 98.8] |
Diagnosis - n (%) | ||
Cellulitis | 48 (38.4) | 20 (62.5) |
Abscess | 47 (37.6) | 4 (12.5) |
Abscess with Surrounding Cellulitis | 30 (24.0) | 8 (25.0) |
Area of Infection (cm2; median [IQR]) | 35.0 [9.0, 124.0] | 319.0 [67.0, 891.0] |
Location - n (%) | ||
Head | 9 (7.2) | 1 (3.1) |
Torso | 20 (16.0) | 1 (3.1) |
Arm | 22 (17.6) | 4 (12.5) |
Hand | 10 (8.0) | 2 (6.3) |
Leg | 35 (28.0) | 11 (34.4) |
Foot | 11 (8.8) | 5 (15.6) |
Multiple Site | 18 (14.4) | 8 (25.0) |
Antibiotics administered in the ED.
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Penicillins - n (%) | 10 (8.0) |
Cephalosporins - n (%) | 23 (18.4) |
Bactrim - n (%) | 36 (28.8) |
Clindamycin - n (%) | 43 (34.4) |
Doxycycline - n (%) | 7 (5.6) |
Vancomycin - n (%) | 20 (16.0) |
Other |
5 (4.0) |
None - n (%) | 9 (7.2) |
Of the 125 patients enrolled, 32 (25.6%) were admitted: 8 (25.0%) to the CDU and 24 (75.0%) to the medical floor. There were no step-down or medical ICU admissions. Among those admitted, median age was 58 years (IQR: 37-68 years, mean: 54.9 years) and 18 (56.3%) were male. Selected comorbidities of admitted participants were diabetes mellitus in 9 (28.1%), liver disease in 4 (12.5%), chronic edema in 15 (46.9%), venous insufficiency in 9 (28.1%), and chronic leg ulcers in 5 (15.6%). Sixteen (50.0%) had received antibiotics in the prior month and 15 (46.9%) had been diagnosed with a SSTI in the prior year. Nine (28.1%) had undergone recent surgery in the SSTI. Further demographics and background statistics of those admitted are also found in Table
For the 32 patients that providers judged as requiring admission, providers noted that infection size influenced their decision in 14 (43.8%) cases, infection location in 6 (18.9%) cases, presence of comorbidities in 18 (56.3%), systemic signs of infection in 7 (21.9%) cases, immunosuppression in 2 (6.3%) cases, and failure of prior treatment in 9 (28.1%) cases. Physician reasons for admission can be seen in Table
Physician reasoning for disposition decisions.
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Infection Size - n (%) | 66 (71.0) | 14 (43.8) |
Infection Location - n (%) | 23 (24.7) | 6 (18.8) |
Comorbidities - n (%) | 0 (0.0) | 18 (56.3) |
Absence of Comorbidities - n (%) | 55 (59.1) | 0 (0.0) |
Systemic Signs - n (%) | 0 (0.0) | 7 (21.9) |
Absence of Systemic Signs - n (%) | 2 (2.2) | 0 (0.0) |
Immunosuppressed Patient - n (%) | 0 (0.0) | 2 (6.3) |
Failure of Prior Treatment - n (%) | 0 (0.0) | 9 (28.1) |
Multiple reasons - n (%) | 81 (87.1%) | 24 (75.0%) |
Follow-up contact was made with 77 (61.6%) of the participants; for those who failed telephone follow-up, the EMR was reviewed and no return ED visits were found for the same infection. Treatment failure was demonstrated in only 19 (24.7%) of those contacted. Of those reporting treatment failure, 16 (84.2%) had a change in antibiotics, 4 (21.2%) returned to the ED, and 3 (15.8%) required repeat hospitalization. Median age of patients failing treatment was 58 years (IQR: 36-68 years, mean: 55.0 years) while the median age of those with successful clinical treatment was 39 years (IQR: 30-50 years, mean: 41.7 years). Median area of infection was 142.0 cm2 (IQR: 35.0 -700.0 cm2, mean: 625.7 cm2) for those failing treatment and 24.3 cm2 (IQR: 7.0-67.0 cm2, mean: 124.0 cm2) in patients successfully treated.
Ninety-three (74.4%) participants received a discharge home. The median age was 39 years (IQR: 29-49 years, mean: 43.3 years) for those discharged home. Two-sample
Two-sample
Our data demonstrated an overall admission rate of 25.6% between the CDU (6.4%) and medical floor (19.2%). This rate of admission was greater than prior studies hoping to elucidate factors associated with patient disposition [
Our data showed that the age of the patient population admitted to either the CDU or the medical floor was significantly greater than that of the population discharged to home. Age has been both replicated and discounted as a factor in admission [
Recent antibiotic use has also been demonstrated in multiple cohorts to be a predictor of inpatient admission [
It was surprising that no particular comorbidity or location of infection was associated with the decision not to discharge a patient to home. However, Talan et al. found a significant relationship between the presence of any comorbidity and admission [
LOS was significantly longer than the anticipated length of stay in our study, though by less than one day. This could be a result of the admitted patients suffering much more severe disease than is typical, provider underestimation of illness severity, or minor systems-based issues in coordination of patient care. The true cause is not clear from the data.
Our treatment failure rate of 24.7% is comparable with that found in other studies that examined outpatient, inpatient, and ED treatment failure, which ranged from 18.7% to 32.1% [
The measured size of the area of infection was not significantly associated with likelihood of treatment failure in our study. Prior studies have reached mixed conclusions, but it appears that physician use of infection size as a decision point for admission may be warranted given this result [
Perhaps most interestingly, the odds of treatment failure were significantly increased with both IV antibiotics and admission. Along with the study data suggesting longer than anticipated stays in the hospital, this result could point even more strongly toward provider underestimation of illness severity in patients they deem worthy of admission. Another explanation is that the choice of antibiotic was left to the discretion of the treating provider, with significant variability between providers known to exist. This is likely to be especially true between the ED and medical floors where a switch from broad spectrum to narrower spectrum antibiotics is often made. Supporting this reasoning is the fact that most of treatment failures in this study resulted from antibiotic changes. Interplay between the initial infective species and the influence of resistant organisms in the hospital environment can also not be discounted. Given the ambiguity in interpreting this information, further study is warranted on this matter.
This study does have some limitations which should be noted. Despite the strength of the prospective study design, the single enrollment center, small number of participants, and the necessity of enrolling patients by convenience sample within an established hourly time frame allow significant possibility of sampling bias. The low successful follow-up rate may also lead to a sampling bias, most directly affecting analysis of treatment failure. The majority of those lost to follow-up were discharged home and presumably less likely to fail treatment, resulting in a greater proportion of inpatient treatment failure to outpatient treatment failures than might otherwise be expected. Finally, the study cohort was predominantly discharged home, with no patients admitted to step-down or medical ICU. This indicates that conclusions drawn from the cohort may not be generalizable to an ED population with a higher severity of illness. Our rates of patients who admit to IV drug use may be different than other communities.
Our study found that increasing age, size of infection, IVDU, and recent antibiotic use were correlated with an increased likelihood of admission to the CDU or medical floor, while previously demonstrated predictors such as individual comorbidities and infection location did not. Despite this lack of association, providers often cited patient comorbidity as a factor in their decision. Size of infection was also heavily cited as a factor in the decision to admit. Treatment failure was once again positively correlated with age but did not demonstrate association with size of infection or prior antibiotic use. Our data were differentiated from prior work in that recent surgery around infection, IV antibiotic administration, and admission were independently associated with treatment failure to a great degree. The reason for these associations is not clear and would require further investigation.
Datasets will not be made available.
The authors declare that they have no conflicts of interest concerning this study.
This study was funded by departmental funds only.