What are the most clinically useful cutoffs for the Alvarado and Pediatric Appendicitis Scores? A systematic review.

STUDY OBJECTIVE: The objective of this study is to systematically review the accuracy of the Alvarado score and Pediatric Appendicitis Score and to identify optimal cutoffs for low- and high-risk populations.

METHODS: We performed a systematic review of the literature and identified 26 studies of the accuracy of the Alvarado score and Pediatric Appendicitis Score. Data were abstracted in parallel, and only prospective, cohort studies that avoided verification bias were included. We calculated summary likelihood ratios for low-, moderate-, and high-risk groups, using all possible cutoffs based on available data, even if not reported in the original study.

RESULTS: The pretest probability of appendicitis was approximately 33% in studies of children and approximately 66% in studies of adults. Likelihood ratios at different cutoffs for the Alvarado score in adults were as follows: 0.03 (<4 points), 0.42 (4 to 6 points), and 3.4 (≥ 7 points); and 0.01 (<5 points), 0.98 (5 to 8 points), and 6.7 (≥ 9 points). Likelihood ratios for the Alvarado score in children were as follows: 0.02 (<4 points), 0.27 (4 to 6 points), and 4.2 (≥ 7 points); and 0.04 (<5 points), 1.2 (5 to 8 points), and 8.5 (≥ 9 points). For the Pediatric Appendicitis Score, likelihood ratios were 0.13 (<4 points), 0.70 (4 to 7 points), and 8.1 (≥ 8 points).

CONCLUSION: For children with a pretest probability of acute appendicitis of 60% or less, an Alvarado score below 4 rules out the diagnosis; this is also true for a score less than 5 if the pretest probability is up to approximately 40%. In adults with a pretest probability greater than or equal to 60%, an Alvarado score of 8 or higher rules in the diagnosis, whereas one of 9 or higher rules in the diagnosis at pretest probabilities greater than or equal to 40%. The Pediatric Appendicitis Score did not identify clinically useful low- or high-risk groups at typical pretest probabilities.