Newer glomerular filtration rate estimating equations for the full age spectrum based on serum creatinine and cystatin C in predicting mortality in patients with ischemic stroke

Background: Renal dysfunction is associated with increased risk of mortality. The novel Full Age Spectrum (FAS) equations estimating the glomerular filtration rate (GFR) based on serum creatinine (FAScrea) and cystatin C (FAScysC) are validated across the entire age spectrum and are superior markers of renal function compared to other equations. Possible association of these equations with mortality in patients with ischemic stroke is not known. Patients and methods: We included 390 patients (207 men, 183 women) in our observational cohort study who had suffered from an ischemic stroke and followed-up on for 3 years. Serum creatinine and cystatin C were measured at admission; GFR was estimated according to the FAScrea, CKD-EPlcrea, FAScysC and CKD-EPIcysC equations. The values of estimated GFRs were divided into quintiles. Results: During the follow-up period, 173 (44.4%) patients died. The association of hazard ratios for FAScrea and CKD-EPlcrea with all-cause mortality was J-shaped and only significantly higher when comparing the fifth quintile hazard ratio for mortality with the first quintile (P < 0.001). For FAScysC and CKD-EPIcysC, hazard ratios increased from the first to the fifth quintile linearly. In an adjusted analysis, FAScrea and CKD-EPlcrea were not associated with all-cause mortality and the hazard ratios of the fifth quintile of FAScysC (P = 0.008) and CKD-EPIcysC (P = 0.042) were significantly associated with mortality compared to the first quintile. Conclusions: In patients with an ischemic stroke, estimated GFR based on serum cystatin (FAScysC and CKDEPIcysC) was a better predictor of all-cause and cardiovascular mortality than estimated GFR based on serum creatinine.