Point-of-Care Ultrasonography for the Diagnosis of Skin and Soft Tissue Abscesses: A Systematic Review and Meta-analysis.

Study Objective: Skin and soft tissue infections are a common chief complaint in the emergency department. Research has shown that clinical examination alone can be unreliable in distinguishing between cellulitis and abscesses, a distinction that is important because they each require different treatments. Point-of-care ultrasonography has been increasingly studied as a tool to improve the diagnostic accuracy for these skin and soft tissue infections. The primary objective of this systematic review is to evaluate the diagnostic accuracy of point-of-care ultrasonography for abscesses. Subgroup analyses are performed for adult versus pediatric patients and high suspicion versus clinically unclear cases. Secondary objectives include the percentage of correct versus incorrect changes in management and reduction in treatment failures because of point-of-care ultrasonography.

Methods: PubMed, Scopus, Latin American and Caribbean Health Sciences Literature database, Cumulative Index of Nursing and Allied Health, Google Scholar, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials were assessed from inception to July 26, 2019, for all prospective studies assessing the diagnostic accuracy of point-of-care ultrasonography for evaluation of skin and soft tissue abscesses. Data were dual extracted into a predefined work sheet and quality analysis was performed with the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Diagnostic accuracy was reported as sensitivity, specificity, positive likelihood ratio (LR+), and negative likelihood ratio (LR-), with 95% confidence intervals (CIs).

Results: We identified 14 studies comprising 2,656 total patients. Point-of-care ultrasonography was 94.6% sensitive (95% CI 89.4% to 97.4%) and 85.4% specific (95% CI 78.9% to 90.2%), with an LR+ of 6.5 (95% CI 4.4 to 9.6) and LR- of 0.06 (95% CI 0.03 to 0.13). Among cases with a high pretest suspicion for abscess or cellulitis, point-of-care ultrasonography was 93.5% sensitive (95% CI 90.4% to 95.7%) and 89.1% specific (95% CI 78.3% to 94.9%), with an LR+ of 8.6 (95% CI 4.1 to 18.1) and LR- of 0.07 (95% CI 0.05 to 0.12). Among cases that were clinically unclear, point-of-care ultrasonography was 91.9% sensitive (95% CI 77.5% to 97.4%) and 76.9% specific (95% CI 65.3% to 85.5%), with an LR+ of 4.0 (95% CI 2.5 to 6.3) and LR- of 0.11 (95% CI 0.03 to 0.32). Among adults, point-of-care ultrasonography was 98.7% sensitive (95% CI 95.3% to 99.8%) and 91.0% specific (95% CI 84.4% to 95.4%), with an LR+ of 10.9 (95% CI 6.2 to 19.2) and LR- of 0.01 (95% CI 0.001 to 0.06). Among pediatric patients, point-of-care ultrasonography was 89.9% sensitive (95% CI 81.8% to 94.6%) and 79.9% specific (95% CI 71.5% to 86.3%), with an LR+ of 4.5 (95% CI 3.1 to 6.4) and LR- of 0.13 (95% CI 0.07 to 0.23). Point-of-care ultrasonography led to a correct change in management in 10.3% of cases (95% CI 8.9% to 11.8%) and led to an incorrect change in management in 0.7% of cases (95% CI 0.3% to 1.1%).

Conclusion: According to the current data, point-of-care ultrasonography has good diagnostic accuracy for differentiating abscesses from cellulitis and led to a correct change in management in 10% of cases. Future studies should determine the ideal training and image acquisition protocols.