Diagnostic values of ultrasound and the Modified Alvarado Scoring System in acute appendicitis

Abstract

Background: Making the diagnosis of acute appendicitis is difficult, and is important for preventing perforation of the appendix and negative appendectomy results. Ultrasound and clinical scoring systems are very helpful in making the diagnosis. Ultrasound is non-invasive, available and cost-effective, and can accomplish more than CT scans. However, there is no certainty about its effect on the clinical outcomes of patients, and it is operator dependent. Counting the neutrophils as a parameter of the Alvarado Scale is not routine in many laboratories, so we decided to evaluate the diagnostic value of the Modified Alvarado Scaling System (MASS) by omitting the neutrophil count and ultrasonography.

Methods: After ethical approval of methodology in Tehran University of Medical Sciences ethical committee, we collected the data. During 9 months, 75 patients with right lower quadrant pain were enrolled in the study, and underwent abdominal ultrasonography and appendectomy, with pathological evaluation of the appendix. The MASS score was calculated for these patients and compared with pathology results.

Results: Fifty-five male and 20 female patients were assessed. Of these patients 89.3% had acute appendicitis. The sensitivity, specificity, PPV, NPV and accuracy rate of ultrasonography was 71.2%, 83.3%, 97.4%, 25% and 72.4%, respectively. By taking a cutoff point of 7 for the MASS score, a sensitivity of 65.7%, specificity of 37.5%, PPV of 89.8%, NPV of 11.5% and accuracy of 62.7% were calculated. Using the cutoff point of 6, a sensitivity of 85.1%, specificity of 25%, PPV of 90.5%, NPV of 16.7% and accuracy of 78.7% were obtained.

Conclusion: Ultrasound provides reliable findings for helping to diagnose acute appendicitis in our hospital. A cutoff point of 6 for the MASS score will yield more sensitivity and a better diagnosis of appendicitis, though with an increase in negative appendectomy.

Figure 1

Modified Alvarado Scoring System with cutoff points of 6 and 7.

Figure 2

ROC curve for diagnosis of acute appendicitis according to the Modified Alvarado Scoring System. The area under the curve is 0.837 with a standard error of 0.67 and confidence interval of 0.705 to 0.968.