The Massachusetts abscess rule: a clinical decision rule using ultrasound to identify methicillin-resistant Staphylococcus aureus in skin abscesses

Validation of a Clinical Decision Rule for Ultrasound Identification of MRSA Skin Abscesses in Children

OBJECTIVE

The aim of this study was to validate an adult-derived clinical decision rule for ultrasound identification of methicillin-resistant Staphylococcus aureus (MRSA) skin abscesses in a pediatric cohort.

METHODS

We conducted a retrospective study of skin and soft tissue infections in patients <21 years presenting to the emergency department who had radiology performed ultrasounds completed and wound cultures obtained. Ultrasound scans were reviewed for edge definition, volume, and shape by 2 pediatric emergency physicians with expertise in point-of-care ultrasound, with approximately 25% of scans reviewed by both experts to evaluate interrater reliability. A third, blinded expert weighed in for discrepancies before analysis. Test performance characteristics were calculated for the clinical decision rule in children.

RESULTS

Two hundred nine patients were enrolled, with mean age of 9.8 (±6.7) years; 87 (42%) were male. Sixty-nine (33%) patients had a wound culture positive for MRSA. The clinical decision rule had a sensitivity of 86% (95% confidence interval [CI], 75%-93%), specificity of 32% (95% CI, 25%-41%), positive predictive value of 38% (95% CI, 35%-42%), negative predictive value of 82% (95% CI, 71%-89%), positive likelihood ratio of 1.26 (95% CI, 1.08-1.46), negative likelihood ratio of 0.45 (95% CI, 0.24-0.84), and an odds ratio of 2.8 (95% CI, 1.31-5.97).

CONCLUSIONS

This clinical decision rule for ultrasound identification of MRSA abscesses had moderately high sensitivity and negative predictive value in pediatric patients, with similar sensitivity compared with the original adult validation group. Ultrasound may help identify MRSA abscesses, allowing for improved antibiotic choices and outcomes for children with MRSA abscesses.

Sonographically Occult Abscesses of the Buttock and Perineum in Children

BACKGROUND

Ultrasound (US) is used to differentiate abscess from cellulitis. At our institution, we observed children who had purulent fluid obtained after a negative abscess US. We sought to determine the incidence of sonographically occult abscess (SOA) of the buttock and perineum, and identify associated clinical and demographic characteristics.

METHODS

Retrospective chart review including children younger than 18 years old presenting to pediatric emergency department with soft tissue infection of the buttock or perineum and diagnostic radiology US read as negative for abscess. We defined SOA as wound culture growing pathogenic organism obtained within 48 hours of the US. Clinical and demographic characteristics included age, sex, race, ethnicity, fever, history of spontaneous drainage, duration of symptoms, previous methicillin resistant Staphylococcus aureus (MRSA) infection, or previous abscess. We used univariate and multivariate logistic regression to assess correlation between these characteristics and SOA.

RESULTS

A total of 217 children were included. Sixty-one (28%) children had SOA; 33 of 61 (54%) had incision and drainage within 4 hours of the US. Of children with SOA, 49 (80%) grew MRSA and 12 (20%) grew methicillin-sensitive S. aureus. In univariate analysis, a history of MRSA, symptom duration 4 days or less, age of younger than 4 years, and Hispanic ethnicity increased the odds of having SOA. In multivariate analysis, history of MRSA and duration of 4 days or less were associated with SOA.

CONCLUSIONS

Twenty-eight percent of children in our institution with US of the buttock and perineum negative for abscess had clinical abscess within 48 hours, most within 4 hours. History of MRSA and shorter symptom duration increased the odds of SOA.

Approach to the Patient with a Skin and Soft Tissue Infection

The diagnosis of a skin and soft tissue infection (SSTI) requires careful attention to a patient's history, physical examination, and diagnostic test results. We review for many bacterial, viral, fungal, and parasitic pathogens that cause SSTIs the clues for reaching a diagnosis, including reported past medical history, hobbies and behaviors, travel, insect bites, exposure to other people and to animals, environmental exposures to water, soil, or sand, as well as the anatomic site of skin lesions, their morphology on examination, and their evolution over time. Laboratory and radiographic tests are discussed that may be used to confirm a specific diagnosis.

Does Point-of-Care Ultrasound Affect Outcomes in Pediatric Patients with Skin and Soft Tissue Infections?

OBJECTIVE

There is increasing evidence for the use of point-of-care ultrasound (POCUS) in pediatric patients with skin and soft tissue infections (SSTI), but there is a lack of sufficient data on its impact on SSTI outcomes. The objective of this study was to determine whether POCUS use is associated with fewer complications after discharge from the pediatric emergency department.

METHODS

This was a prospective cohort study in patients presenting to the emergency department with SSTI between the ages of 2 months and 19 years old. Adverse outcomes included hospitalization after discharge, change in antibiotics, subsequent procedures, or reevaluation by a medical professional. Outcome information was obtained 1 week later. Descriptive statistics and χ² tests were used.

RESULTS

Of 456 patients screened, 250 were enrolled. POCUS was performed on 113 (45%) patients. The median age was 5 years, with more females in the non-POCUS group compared with the POCUS group (58% vs. 52%). Cellulitis without abscess was more commonly diagnosed in the POCUS group than in the non-POCUS group (26% vs 14%, P = 0.02.) The patients in the non-POCUS group were more likely to undergo incision and drainage than those in the POCUS group (62% vs 45%, P = 0.008). Overall, a greater number of patients in the POCUS group did not undergo any procedure (45% vs 27%, P = 0.003). The outcomes at 1 week did not differ significantly between the two groups.

CONCLUSIONS

POCUS use may lead to fewer procedures, but it does not lead to significantly better outcomes. Large randomized controlled trials are needed to confirm or refute our findings.

Abscess Management: An Evidence-Based Review for Emergency Medicine Clinicians

BACKGROUND

Abscesses are commonly evaluated and managed in the emergency department. Recent research has evaluated the use of ultrasonography, packing, incision and drainage (I&D), and antibiotics. There are evidence-based nuances to the management of specific types of abscesses, such as Bartholin, breast, dental, hidradenitis suppurativa, peritonsillar, and pilonidal abscesses.

OBJECTIVE

This review provides emergency medicine clinicians with a summary of the current literature regarding abscess management in the emergency department.

DISCUSSION

Ultrasound is valuable in diagnosing abscesses that are not clinically evident and in guiding I&D procedures. Although I&D is traditionally followed by packing, this practice may be unnecessary for small abscesses. Antibiotics, needle aspiration, and loop drainage are suitable alternatives to I&D of abscesses with certain characteristics. Oral antibiotics can improve outcomes after I&D, although this improvement must be weighed against potential risks. Many strategies are useful in managing Bartholin abscesses, with the Word catheter proving consistently effective. Needle aspiration is the recommended first-line therapy for small breast abscesses. Dental abscesses are often diagnosed with clinical examination alone, but ultrasound may be a useful adjunct. Acute abscess formation caused by hidradenitis suppurativa should be managed surgically by excision when possible, because I&D has a high rate of abscess recurrence. Peritonsillar abscesses can be diagnosed with either intraoral or transcervical ultrasound if clinical examination is inconclusive. Needle aspiration and I&D are both suitable for the management of peritonsillar abscesses. Pilonidal abscesses have traditionally been managed with I&D, but needle aspiration with antibiotics may be a suitable alternative.

CONCLUSIONS

This review evaluates the recent literature surrounding abscess management for emergency medicine clinicians.

Ultrasound features of purulent skin and soft tissue infection without abscess

PURPOSE

Ultrasound (US) aids clinical management of skin and soft tissue infection (SSTI) by differentiating non-purulent cellulitis from abscess. However, purulent SSTI may be present without abscess. Guidelines recommend incision and drainage (I & D) for purulent SSTI, but US descriptions of purulent SSTI without abscess are lacking.

METHODS

We retrospectively reviewed pediatric emergency department patients with US of the buttock read as negative for abscess. We identified US features of SSTI with adequate interobserver agreement (kappa > 0.45). Six independent observers then ranked presence or absence of these features on US exams. We studied association between US features and positive wound culture using logistic regression models (significance at p < 0.05).

RESULTS

Of 217 children, 35 patients (16%) had cultures positive for pathogens by 8 h after US and 61 patients (32%) had cultures positive by 48 h after US. We found kappa > 0.45 for focal collection > 1.0 cm (κ = 0.57), hyperemia (κ = 0.57), swirling with compression (κ = 0.52), posterior acoustic enhancement (κ = 0.47), and cobblestoning or branching interstitial fluid (κ = 0.45). Only cobblestoning or interstitial fluid was associated with positive wound cultures in logistic regression models at 8 and 48 h.

CONCLUSIONS

Cobblestoning or interstitial fluid on US may indicate presence of culture-positive, purulent SSTI in patients without US appearance of abscess. Although our study has limitations due to its retrospective design, this US appearance should alert imagers that the patient may benefit from early I & D.

Ultrasound-Guided Drainage for Pediatric Soft Tissue Abscesses Decreases Clinical Failure Rates Compared to Drainage Without Ultrasound: A Retrospective Study

OBJECTIVES

Soft tissue abscesses are common in the pediatric emergency department (ED). Ultrasound (US) can be used to both diagnose soft tissue abscesses as well as guide drainage. We hypothesized that clinical failure rates would be less in pediatric patients with suspected skin abscesses when evaluated with US.

METHODS

We performed a retrospective review of suspected pediatric skin abscesses at 4 EDs over a 22-month period. Cases were identified through electronic medical record descriptions, discharge diagnoses, and US database records. Data on US use, findings, and outcomes were abstracted to an electronic database. Comparisons between groups included US versus non-US (primary outcome) as well as surgical drainage vs nonsurgical drainage (secondary outcome).

RESULTS

A total of 377 patients were seen with concern for a potential skin abscess; 141 patients (37.4%) underwent US imaging during their visit, and 239 (63.4%) underwent incision and drainage (I&D) during their ED stay: 90 with US and 149 without. The failure rate for patients evaluated with US was significantly lower than that for those evaluated without US (4.4% versus 15.6%; P < .005). Thirty-four (11.3%) of the 302 patients with a diagnosis of an abscess failed therapy: 19 (8.2%) after I&D and 15 (21.1%) after nonsurgical management. Failure after I&D was associated with a smaller abscess cavity on US imaging (17.2 versus 44.8 mm³ ; P < .05).

CONCLUSIONS

The use of US for patients with a suspected skin abscess was associated with a reduction in the amount of clinical failure rates after both surgical drainage and nonsurgical therapy. Ultrasound should be used when evaluating or treating patients with abscesses.

Diagnosis and management of skin and soft-tissue infections (SSTI). A literature review and consensus statement: an update

Skin and soft-tissue infections (SSTIs) are among the most common bacterial infections, posing considerable diagnostic and therapeutic challenges. Fourteen members of the Italian Society of Infectious Diseases, after a careful review of the most recent literature using Medline database and their own clinical experience, updated a previous paper published in 2011 by preparing a draught manuscript of the statements. The manuscript was successively reviewed by all members and ultimately re-formulated the present manuscript during a full day consensus meeting. The microbiological and clinical aspects together with diagnostic features were considered for necrotizing and not necrotizing SSTIs in the light of the most recent guidelines and evidences published in the last five years. The antimicrobial therapy was considered as well - both empirical and targeted to methicillin-resistant Staphylococcus aureus and/or other pathogens, also taking into account the epidemiological and bacterial resistance data and the availability of new antibacterial agents.

Pediatric emergency medicine point-of-care ultrasound: summary of the evidence

The utility of point-of-care ultrasound is well supported by the medical literature. Consequently, pediatric emergency medicine providers have embraced this technology in everyday practice. Recently, the American Academy of Pediatrics published a policy statement endorsing the use of point-of-care ultrasound by pediatric emergency medicine providers.  To date, there is no standard guideline for the practice of point-of-care ultrasound for this specialty. This document serves as an initial step in the detailed "how to" and description of individual point-of-care ultrasound examinations.  Pediatric emergency medicine providers should refer to this paper as reference for published research, objectives for learners, and standardized reporting guidelines.

Scratching the surface: a review of skin and soft tissue infections in children

PURPOSE OF REVIEW

We present data from recently conducted research on the diagnosis and management of skin and soft tissue infections (SSTIs) in children.

RECENT FINDINGS

Current research in the area of SSTIs (cellulitis and abscess) has focused on the use of ultrasound, risk factors associated with bacteremia, antibiotic choice, and incision and drainage (I&D) practices. When clinical examination is equivocal at distinguishing abscess from cellulitis, ultrasound can aid in the diagnosis and alter management. Bacteremia is rare in immunocompetent children with uncomplicated SSTIs; blood cultures may be reserved for complicated cases and for those who are systemically ill. Despite the increased prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), I&D without antibiotics remains the first-line therapy for abscess. Antibiotics for uncomplicated cellulitis should target β-hemolytic streptococci and methicillin-susceptible S. aureus (MSSA). There are significant variations in pain and sedation practices for I&D, with substantive evidence for the use of topical anesthetics. Wound packing after I&D may not confer significant benefit.

SUMMARY

Evidence to aid in the diagnosis and management of SSTIs in children has emerged in recent years; however, larger prospective pediatric studies are needed.