External validation of P2/MS and comparison with other simple non-invasive indices for predicting liver fibrosis in HBV-infected patients

Background: To optimize management strategies and predict the long-term clinical course in patients with chronic hepatitis B (CHB), non-invasive tests to determine the degree of hepatic fibrosis have been developed. Aims: We aimed to conduct a large-scale external validation of a simple, non-invasive test called P2/MS using CHB patients and to compare it to other non-invasive tests for the prediction of histological cirrhosis. Methods: From 2006 to 2009, we enrolled a total of 521 consecutive CHB patients who underwent liver biopsy. Fibrosis stage was assessed according to the Metavir scoring system by a single pathologist who was unaware of the patients' histories. Results: For predictions of significant (p ≥ 2) and severe (p ≥ 3) fibrosis and cirrhosis (p = 4), the areas under the receiver operating characteristic curves were 0.801, 0.856, and 0.906, respectively. In predicting cirrhosis, we found that diagnostic values were comparable to age-spleen platelet ratio index (0.931, p = 0.063), spleen-platelet ratio index (0.923, p = 0.145), age-platelet index (0.914, p = 0.670), and FIB-4 (0.898. p = 0.597) and had better outcomes than the aspartate aminotransferase (AST)-platelet ratio index (0.780, p < 0.001), and AST-alanine aminotransferase ratio index (0.729, p < 0.001). The cut-off points of P2/MS >83 and P2/MS <30 provided 91.1% of negative predictive value and 91.3% of positive predictive value, respectively. Based on these results, liver biopsies could be avoided in 67.0% of the population. These cut-offs were validated internally using bootstrap resampling methods, which showed good agreement. Conclusions: P2/MS is a simple, accurate, and inexpensive method with comparable outcomes to other non-invasive tests and may reduce the need for liver biopsy in the majority of CHB patients.