Diagnostic accuracy of the gamma-glutamyl transpeptidase to platelet ratio (GPR) using transient elastography as a reference

We read with great interest the letter from Stockdale et al 1 in which they concluded that the gamma-glutamyl transpeptidase to platelet ratio (GPR) and aspartate transaminase (AST)-to-platelet ratio index (APRI) would not be ideal for the diagnosis of liver fibrosis in patients with HIV–HBV coinfection from West Africa. In a relatively small cohort of HIV–HBV coinfected subjects (n=100) from Ghana, the authors reported poor sensitivity (57%–67%) and specificity (63%–79%) of GRP and APRI in diagnosing advanced fibrosis (≥F3) and cirrhosis (F4). These findings are interesting, but should be interpreted with caution with regards to the internal validity of using transient elastography as the reference, the study population itself and the cut-offs generated as a result. The GPR was originally developed for the assessment of liver fibrosis in HBV mono-infected individuals in a West African setting.2 It has been recently applied to patients predominately treated for HIV–HBV coinfection by a French team, reporting good diagnostic performance to diagnose cirrhosis (sensitivity 77%, specificity 87%).3 In both studies, the accuracy of GPR was assessed …