• Daniel J Kim, Justin E Burton, Abdullah Hammad, Vikram Sabhaney, Jason Freder, Jeffrey N Bone, and Justin S Ahn.
• Department of Emergency Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
• Acad Emerg Med. 2023 Aug 1; 30 (8): 859869859-869.

BackgroundDistinguishing peritonsillar abscess (PTA) from peritonsillar cellulitis using clinical assessment is challenging as many features overlap for both conditions, and physical examination is only about 75% sensitive and 50% specific for diagnosing PTA. The primary objective of this systematic review was to determine the test characteristics of ultrasound for diagnosing PTA when compared to a reference standard of computed tomography or acquisition of pus via needle aspiration or incision and drainage.MethodsThis systematic review was performed in accordance with the Preferred Reporting Items for a Systematic Review and Meta-analysis of Diagnostic Test Accuracy (PRISMA-DTA) guidelines. We searched seven databases from 1960 to November 2022. Two independent reviewers completed study selection, data extraction, and QUADAS-2 risk-of-bias assessment. We used a bivariate random-effects model to calculate pooled sensitivity, specificity, positive likelihood ratio (LR+), and negative likelihood ratio (LR-). We also conducted subgroup analyses on radiology ultrasound compared to point-of-care ultrasound (POCUS) and intraoral compared to transcervical scanning techniques.ResultsFrom 339 citations, we identified 18 studies for inclusion. Because one study only reported positive cases of PTA (thereby preventing the calculation of specificity), it was excluded from the analysis, so the analysis included a total of 17 studies with 812 patients, of whom 541 had PTA. Pooled bivariate sensitivity was 86% (95% confidence interval [CI] 78%-91%), specificity 76% (95% CI 67%-82%), LR+ 3.51 (95% CI 2.59-4.89), and LR- 0.19 (95% CI 0.12-0.30). On subgroup analysis, radiology-performed ultrasound had a sensitivity and specificity of 89% and 71%, compared to POCUS, which had a sensitivity and specificity of 74% and 79%. Comparing the two different techniques, intraoral had a sensitivity and specificity of 91% and 75% while transcervical had a sensitivity and specificity of 80% and 81%.ConclusionsUltrasound demonstrates high sensitivity for ruling out PTA, but it only has moderate specificity for ruling in the diagnosis.© 2023 The Authors. Academic Emergency Medicine published by Wiley Periodicals LLC on behalf of Society for Academic Emergency Medicine.

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