Validation of a simple model for predicting liver fibrosis in HIV/hepatitis C virus-coinfected patients

Objectives Recently, several models incorporating laboratory measurements have been validated for use as surrogate markers for liver fibrosis in hepatitis C virus (HCV) mono-infection, the simplest of these being the aspartate aminotransferase (AST) to platelet ratio index (APRI). We evaluated how well the APRI predicts significant hepatic fibrosis in patients with HIV/HCV coinfection. Methods Forty-six HIV/HCV-coinfected patients who underwent liver biopsy and had concomitant laboratory measurements ( 3 months) were included in the study. Significant fibrosis was defined as F2-F4 using Batt and Ludwig scoring (=3 Ishak). APRI = [(AST/upper limit of normal)/platelet count (10(9)/L)] x 100. We used SAS PROC LOGISTIC (SAS Institute, Cary, NC) to calculate the area under the receiver operating curve (ROC) (AUC). Sensitivities, specificities, positive predictive value (PPV) and negative predictive value (NPV) were compared using cut-offs previously identified in the literature. Results Thirty-three of 46 patients (72%) had significant fibrosis on biopsy. For significant fibrosis, the area under the ROC for the APRI was 0.847 +/- 0.057. APRI scores > 1.5 (the higher cut-off) were 100% specific and 52% sensitive; PPV was 100% and NPV 45%. Scores < 0.5 (the lower cut-off) were 82% sensitive and 46% specific in ruling out significant fibrosis (PPV 79%; NPV 50%). Conclusions A simple model incorporating readily available laboratory data is highly predictive of significant fibrosis in HIV/HCV coinfection and could serve as a biopsy-sparing measure, thus making treatment more accessible for this population.