Poor sensitivity of a modified alvarado score in adults with suspected appendicitis

Study objective: A clinical decision rule that identifies patients at low risk for appendicitis may reduce the reliance on computed tomography (CT) for diagnosis. We seek to prospectively evaluate the accuracy of a low modified Alvarado score in emergency department (ED) patients with suspected appendicitis and compare the score to clinical judgment. We hypothesize that a low modified Alvarado score will have a sufficiently high sensitivity to rule out acute appendicitis. Methods: We performed a prospective observational study of adult patients with suspected appendicitis at 2 academic urban EDs. A low modified Alvarado score was defined as less than 4. The sensitivity and specificity were calculated with 95% confidence interval (CI) for a low modified Alvarado score, and a final diagnosis of appendicitis was confirmed by CT, laparotomy, or 7-day follow-up. Results: Two hundred sixty-one patients were included for analysis (mean age 35 years [range 18 to 89 years], 68% female patients, 52% white). Fifty-three patients (20%) had acute appendicitis. The modified Alvarado score test characteristics demonstrated a sensitivity and specificity of 72% (95% CI 58% to 84%) and 54% (95% CI 47% to 61%), respectively. Unstructured clinical judgment that appendicitis was either the most likely or second most likely diagnosis demonstrated a sensitivity and specificity of 93% (95% CI 82% to 98%) and 33% (95% CI 27% to 40%), respectively. Conclusion: With a sensitivity of 72%, a low modified Alvarado score is less sensitive than clinical judgment in excluding acute appendicitis.