Diagnostic Accuracy of the Modified Alvarado Score and Serum C-reactive Protein in Acute Appendicitis.

Background The Alvarado score is a diagnostic tool to stratify patients on the likelihood of acute appendicitis based on signs, symptoms, and laboratory values. The validity of this score as compared to other diagnostic measures for acute appendicitis is questionable. The current study addresses the use of a modified Alvarado score (MAS) in conjunction with the widely used acute phase reactant biomarker serum C-reactive protein (CRP) for diagnostic accuracy. Objective To determine the diagnostic accuracy in terms of specificity, sensitivity, negative predictive value (NPV), and positive predictive value (PPV) of the combined MAS/CRP keeping histopathological diagnosis of acute appendicitis as a gold standard. Methods This is a cross-sectional validation study carried out in the Department of Surgery, Pakistan Institute of Medical Sciences, Islamabad. A total of 230 patients undergoing appendicectomy for appendicitis were included in the study through non-probability consecutive sampling, with positive histology undetermined. Prior to surgery, the preoperative Alvarado score was calculated and CRP was determined. The appendix removed at surgery was subjected to histopathological examination and on the basis of its report patients were postoperatively diagnosed either as positive or negative for acute appendicitis. Results The mean age of the patients was 22.66±7.48 years. There were 137 (59.6%) males and 93 (40.4%) females. One hundred eighty-three (79.6%) patients had a positive CRP and 47 (20.4%) had a negative CRP. Alvarado scores were calculated and there were 28 (12.1%) patients with a score of ≤ 6, and 202 with a score of 7-9. The appendix removed at surgery was subjected to histopathological examination. One hundred ninety-five (84.7%) patients were positive for acute appendicitis on histopathology and 35 (15.2%) had normal appendix on histopathology. Among the 195 patients with acute appendicitis 178 (91.3%) had positive CRP/MAS and 17 (87.17%) had negative CRP/MAS. Among the 182 patients with positive CRP/MAS; 178 (97.8%) had acute appendicitis and 4 (2.2%) had normal appendix. Among the 48 patients with negative CRP/MAS; 17 (35.4%) had acute appendicitis and 31 (64.3%) had normal appendix. The calculated sensitivity, specificity, PPV, and NPV were 91.2%, 88.5%. 91.8%, and 64.5%, respectively. Conclusion MAS used in combination with CRP is a highly sensitive tool for use in the diagnosis of acute appendicitis and is especially useful in resource-limited healthcare settings and for assistance in decision-making for doctors with less clinical experience.