Systematic Review: Computed Tomography and Ultrasonography To Detect Acute Appendicitis in Adults and Adolescents

BACKGROUND: Although clinicians commonly use computed tomography or ultrasonography to diagnose acute appendicitis, the accuracy of these imaging tests remains unclear. PURPOSE: To review the diagnostic accuracy of computed tomography and ultrasonography in adults and adolescents with suspected acute appendicitis. DATA SOURCES: The authors used MEDLINE, EMBASE, bibliographies, review articles, textbooks, and expert opinion to retrieve English- and non-English-language articles published from 1966 to December 2003. STUDY SELECTION: The authors included prospective studies evaluating computed tomography or ultrasonography followed by surgical confirmation or clinical follow-up in patients at least 14 years of age with suspected appendicitis. DATA EXTRACTION: One assessor (for non-English-language studies) or 2 assessors (for English-language studies) independently reviewed each article to abstract relevant study characteristics and results. DATA SYNTHESIS: Twelve computed tomography studies and 14 ultrasonography studies met inclusion criteria. Computed tomography had an overall sensitivity of 0.94 (95% CI, 0.91 to 0.95), a specificity of 0.95 (CI, 0.93 to 0.96), a positive likelihood ratio of 13.3 (CI, 9.9 to 17.9), and a negative likelihood ratio of 0.09 (CI, 0.07 to 0.12). Ultrasonography had an overall sensitivity of 0.86 (CI, 0.83 to 0.88), a specificity of 0.81 (CI, 0.78 to 0.84), a positive likelihood ratio of 5.8 (CI, 3.5 to 9.5), and a negative likelihood ratio of 0.19 (CI, 0.13 to 0.27). Verification bias and inappropriate blinding of reference standards were noted in all of the included studies. LIMITATIONS: The summary assessment of the diagnostic accuracy for both tests was limited by the small number of studies, heterogeneity among study samples, and poor methodologic quality in the original studies. CONCLUSIONS: Computed tomography is probably more accurate than ultrasonography for diagnosing appendicitis in adults and adolescents. Prospective studies that apply gold standard diagnostic testing to all study participants would more reliably estimate the true diagnostic accuracy of these tests.