A Highly Sensitive and Specific Combined Clinical and Sonographic Score to Diagnose Appendicitis.

Background: CT scanning reduces the negative appendectomy rate however it exposes the patient to ionizing radiation. Ultrasound (US) does not carry this risk but may be non-diagnostic. We hypothesized that a clinical-ultrasound scoring system would improve diagnostic accuracy. Methods: We conducted a retrospective review of all patients (>15 yo) who presented through the emergency department with suspected appendicitis and underwent initial US. An ultrasound score was developed using odds ratios for appendicitis given appendiceal diameter, compressibility, hyperemia, free fluid and focal or diffuse tenderness. The ultrasound score was then combined with the Alvarado score. Final diagnosis of appendicitis was assigned by pathology reports. Results: Three hundred patients who underwent US as initial imaging were identified. Thirty-two patients with evident non-appendiceal pathology on US were excluded. In 114 (38%) the appendix was not visualized and partially visualized in 36 (12%). 57 (21.3%) had an appendectomy with 1 (1.7%) negative. Six non-visualized appendicies underwent appendectomy, with no negative cases. Sensitivity and specificity for the sonographic score were 86% and 90% respectively at a score of 1.5. The combined score demonstrated 98% sensitivity and 82% specificity at 6.5 and 95% sensitivity and 87% specificity at a score of 7.5. Sensitivity and specificity were confirmed by bootstrap resampling for validation. Area under receiver operating characteristic (ROC) curves for our new US score were similar to the ROC curve for the Alvarado score (91.9 and 91.1, p=0.8). The combined US and Alvarado score yielded an AUC of 97.1, significantly better than either score alone (p =0.017 and P

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