A retrospective evaluation of the Modified Alvarado Score for the diagnosis of acute appendicitis in HIV-infected patients

The aim of this study was to evaluate and compare the diagnostic value of a Modified Alvarado Score (MAS) >= 7 for acute appendicitis in both Human Immunodeficiency Virus (HIV)-negative (HIVneg) and positive (HIVpos) patientcohorts. This retrospective study included all HIV-tested patients undergoing appendectomy at a regional hospital from March 2010 to March 2011. The MAS was calculated for all patients, as well as for the HIVneg and HIVpos groups separately. Two subgroups were considered for each of these: MAS >= 7 (high likelihood of appendicitis) and MAS < 7 (low likelihood of appendicitis). These subgroups were then analysed against histopathological findings of the resected appendix. MAS specificities and sensitivities were determined by comparing Receiver Operator Characteristic (ROC) curves for the various scores. The study comprised 133 patients. Eighty-six (65%) were men and the median age was 20 years (range 4-64); 18 patients (14%) were HIVpos. Appendicitis was confirmed histologically in 113 patients, 100 in the HIVneg group and 13 in the HIVpos group. Specificity and sensitivity of a MAS >= 7 for HIVneg patients was 73 and 85% respectively. Based on the ROC curves, HIVpos patients only showed similar sensitivities (69%) and specificities (80%) at a MAS >= 8. A MAS >= 7 is a reliable predictor of acute appendicitis in HIVneg patients. In HIVpos patients, the MAS threshold required to accurately predict appendicitis is 8. The use of a MAS >= 7 in this group of patients will result in unnecessary surgical intervention.