Diagnostic accuracy of computed tomography and ultrasound for the diagnosis of acute appendicitis: A systematic review and meta-analysis

Introduction: The diagnosis of acute appendicitis remains challenging. This review determined the current diagnostic accuracy of CT and ultrasound for suspected acute appendicitis in adults. 

Methods: This systematic review adhered to the PRISMA for diagnostic test accuracy guidelines. A systematic search was undertaken in appropriate databases. Screening of potential titles and abstracts, full-text retrieval, methodological quality assessment using QUADAS, and data extraction was performed. Meta-analyses were performed for relevant subgroups, and sensitivity analysis was completed to account for outliers. GRADE was utilized to assess the certainty of findings. 

Results: 31 studies evaluating CT, 10 evaluating US, and six evaluating both were included. Pooled sensitivity and specificity for CT was 0.972 [0.958, 0.981] and 0.956 [0.941, 0.967] respectively, and 0.821 [0.738, 0.882] and 0.859 [0.727, 0.933] for US, respectively. When analyzing subgroups based on the use of contrast enhancement, sensitivity and specificity was highest for CT with intravenous and oral contrast (0.992 [0.965, 0.998], 0.974 [0.936, 0.99]), compared to CT with intravenous contrast (0.955 [0.922, 0.974], 0.942 [0.916, 0.960]). Low-Dose CT produced comparable values (0.934 [0.885,0.963], 0.937 [0.911, 0.955]) relative to these subgroups and standard dose non-contrast CT (0.877 [0.774,0.937], 0.914 [0.827, 0.959]). US studies which excluded equivocal findings demonstrated significantly greater values than the remainder of US studies (p < 0.0001). 

Conclusion: The updated diagnostic test accuracies of CT, US and relevant subgroups should be implemented in light of factors such as dose, cost, and timing. Implications for practice: For diagnosis of adult acute appendicitis: • CT with intravenous plus oral contrast enhancement yields statistically significantly greater diagnostic accuracy than CT with intravenous contrast alone. • Low-dose CT yields comparable sensitivity and specificity to standard-dose CT. • Ultrasound studies which exclude equivocal results may overinflate sensitivity and specificity.