Thank you for the interest and positive response to our article on the FIB-4 index, a simple, noninvasive model of readily available data to predict advanced fibrosis in patients coinfected with HIV and hepatitis C virus (HCV).1 As concluded in a recent review by Donald Rockey, “The development of safe, inexpensive, and reliable noninvasive fibrosis measurement tools remains a research priority in clinical hepatology.”2 Although several models to achieve this goal have been developed, some require additional tests that are not routine3 while others, like the FIB-4 index, use readily available tests.4 A recent study comparing several noninvasive models in patients with chronic HCV found similar performance between FibroTest, Fibroscan, and AST:Platelet ratio index (APRI).5 Similarly, Sebastiani observed similar overall performance comparing FibroTest and APRI.6
Although our model was not developed in patients with HCV alone, we have no reason to think it would not work equally as well as it did in those with coinfection.7–9 We are happy to see that the FIB-4 index performed extremely well with an area under receiver operating characteristics curve (AUROC) of 0.85 in this large cohort of patients with HCV alone. Similar to our study in coinfected patients,1 approximately 70% of the 919 biopsies were correctly classified, and the FIB-4 showed excellent concordance with the FibroTest. Although we did not show our data, we found that the FIB-4 index outperformed APRI in our coinfected population to predict significant fibrosis (AUROC 0.76 versus 0.70; P = .039). On the basis of these corroborative results, the simplicity of our model, and the ability to calculate this index at the bedside with readily available data, we agree that there is little reason to obtain more expensive tests to predict hepatic fibrosis in the majority of patients with chronic HCV with or without HIV coinfection.