Increased Serum Fibroblast Growth Factor 23 Predicts Mortality in People With HIV/HCV Coinfection.

BACKGROUND

People with HIV and hepatitis C virus (HCV) coinfection experience excess mortality because of multiple causes. Identification of biomarkers associated with mortality beyond that attributable to liver fibrosis may be relevant for prognostication. Fibroblast growth factor 23 (FGF23), a phosphotropic hormone, predicts adverse outcomes in several chronic conditions. We aimed to investigate whether elevated FGF23 predicts all-cause mortality in patients with HIV/HCV coinfection.

METHODS

We included patients with HIV/HCV coinfection from the Canadian Coinfection Cohort with available serum FGF23, fibrosis biomarker fibrosis-4 (FIB-4), and at least 1-year follow-up. Elevated FGF23 and advanced liver fibrosis were defined as FGF23 > 241 reference unit/mL and FIB-4 > 3.25, respectively. All-cause mortality was analyzed using survival analysis. The effect of advanced liver fibrosis as a mediator on mortality was estimated by mediation analysis.

RESULTS

Three hundred twenty-one patients were included (24% with elevated FGF23, 19% with advanced liver fibrosis). During a mean follow-up period of 8.4 years, 34% of the cohort died. The incidence rate of all-cause mortality was higher in patients with elevated FGF23 (66.1 per 1000 person-years, 95% confidence interval 45.8 to 92.3) relative to patients without elevated FGF23 (37.5 per 1000 person-years, 95% confidence interval 29.6 to 46.9). After adjusting for potential confounders, elevated FGF23 was associated with significant direct and indirect effects (mediated through advanced liver fibrosis) on all-cause mortality, with 57% of deaths not mediated through advanced fibrosis.

CONCLUSIONS

In patients with HIV/HCV coinfection, FGF23 may be used as prognostic biomarker for risk stratification accounting also for death causes other than those attributable to liver fibrosis.