γ-Glutamyl Transferase-to-Platelet Ratio in Liver Fibrosis: A Comprehensive Meta-Analysis of Diagnostic Accuracy and Cut-Off Points

Background Non-invasive tests (NITs) for liver fibrosis are accessible and affordable alternatives to liver biopsies. The γ-glutamyl-to-platelet ratio (GPR) has been proposed as a more reliable NIT than other markers; however, aggregate data regarding its performance are lacking. This review is the first comprehensive meta-analysis to assess the diagnostic performance of GPR versus liver biopsy across different diseases and cut-off points. Methods A systematic review was carried out of studies evaluating the use of GPR as a non-invasive test (NIT) for liver fibrosis in comparison to liver biopsy. Bivariate meta-regression analysis was employed to assess the predictive accuracy (sensitivity and specificity) of GPR at various stages of liver fibrosis and explore potential sources of variability. The optimal GPR threshold values for the diagnosis and exclusion of significant fibrosis and cirrhosis were identified. Results Thirty-three studies (N = 16,836 patients) were included in the quantitative analysis. The summary receiver operating characteristic curves (sROC) for F2, F3, and F4 were 0.76 (95% confidence interval (CI) 0.72; 0.78), 0.82 (95% CI 0.79; 0.85), and 0.80 (95% CI 0.72; 0.91), respectively. The pooled sensitivity and specificity of GPR in diagnosing significant fibrosis were 0.65 (95% CI, 0.59–0.71) and 0.74 (95% CI, 0.68–0.78), while for cirrhosis, they were 0.75 (95% CI, 0.68–0.81), and 0.75 (95% CI, 0.69–0.8), respectively. Cut-off points of 0.45 and 1.22 provided 80% sensitivity and 90% specificity for excluding and diagnosing cirrhosis, respectively. Conclusion GPR demonstrated highly reliable sensitivity in ruling out cirrhosis, outperforming existing NITs, while maintaining effectiveness across various liver conditions, underscoring its potential as a versatile non-invasive method for assessing liver fibrosis.