The Article: Becker BA, Kaminstein D, Secko M, Collin M, Kehrl T, Reardon L, Stahlman BA. A prospective, multicenter evaluation of point-of-care ultrasound for appendicitis in the emergency department. Acad Emerg Med. 2022 Feb;29(2):164-173. doi: 10.1111/acem.14378. Epub 2021 Sep 14. PMID: 34420255.
The Idea: Appendicitis is a common entity in the ED that often requires imaging to diagnose for eventual surgical management. POCUS diagnosis of appendicitis has become more popular given the safety and efficiency of ultrasound. Other single center studies have been conducted with wide variability in disease prevalence, making it difficult to discern the accuracy of the test.
The Study: This is a two-center, prospective, observational study aimed at determining the accuracy of POCUS performed by senior resident, ultrasound fellow, and attendings emergency physicians in diagnosing appendicitis. All participating sonographers received a 30-minute lecture on POCUS technique for appendicitis beforehand, POCUS became standard of care for credentialed providers during the study period, and a standardized checklist was required for each scan. Expert ultrasound trained reviewers additionally completed blind image interpretations for all scans.
Inclusion Criteria: A convenience sample of adult and pediatric ED patients presenting between July 2014 and February 2020 with suspicion for appendicitis who were identified by direct clinical contact by a member of the study team or referral by a provider in the ED.
Exclusion Criteria: Having previously undergone radiology imaging for suspicion of appendicitis, pregnant patients, incarcerated patients, non-English speaking patients.
Primary Outcome: Acute appendicitis as confirmed by pathology reports following appendectomy or, rarely, managed nonoperatively despite lack of pathologic confirmation. Negative cases were those without any diagnoses of appendicitis at the index visit or reported on follow up call two weeks later.
Sonographic impressions after utilizing the checklist were as follows: (1) normal, appendix not visualized; (2) normal, appendix visualized; (3) appendicitis; or (4) indeterminate.
The Results: Primary analysis of the 256 patients (median age 19) showed a sensitivity of 0.85, specificity 0.63, +LR 2.29, and -LR 0.24, all of which were statistically significant. Expert review was surprisingly (though not significantly) less sensitive and nearly equally specific, with a moderate kappa of 0.436. In subgroup analysis, POCUS was more accurate in pediatric patients and in adults with BMI < 30. Reclassifying indeterminate POCUS interpretations as negative decreased sensitivity to 0.60 and increased specificity to 0.88 for POC sonographers. Notably, all lost to follow up patients were considered as cases of missed appendicitis.
The Limitations: Over 80% of the patients were from one of the two study sites; predominately attending physicians performed scans and were more sensitive and specific in doing so which may make results less generalizable to residency institutions; three highly skilled physician sonographers made up 45% of the scans with extraordinary accuracy which may skew the generalizability of results; sample of convenience introduces potential biases
The Takeaway: POCUS performed by emergency physicians is moderately accurate for acute appendicitis after a brief departmental training but is not able to function as a definitive test. Data from high frequency scanners suggests that increased physician experience with scans may increase the diagnostic accuracy of the sonographic evaluation.
Author: Christopher Karousatos, MD