Chronic kidney disease, cardiovascular risk markers and total mortality in older men: cystatin C versus creatinine.

Background: It remains uncertain whether cystatin C is a superior marker of renal function than creatinine in older adults. We have investigated the association between estimated glomerular filtration rate (eGFR) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations based on creatinine (CKD-EPIcr) and cystatin C (CKD-EPIcys), and cardiovascular risk markers and mortality in older adults.

Methods: This is a cross-sectional and prospective study of 1639 British men aged 71-92 years followed up for an average of 5 years for mortality. Cox survival model and receiving operating characteristic analysis were used to assess the associations.

Results: The prevalence of chronic kidney disease (CKD) was similar using the two CKD-EPI equations, although cystatin C reclassified 43.9% of those with stage 3a CKD (eGFR 45-59 mL/min/1.73, moderate damage) to no CKD. However, CKD stages assessed using both CKD-EPIcr and CKD-EPIcys were significantly associated with vascular risk markers and with all-cause and cardiovascular disease mortality. In all men with CKD (eGFR <60 mL/min/1.73), the HRs (95% CI) for all-cause mortality after adjustment for cardiovascular risk factors compared with those with no CKD were 1.53 (1.20 to 1.96) and 1.74 (1.35 to 2.23) using CKD-EPIcr and CKD-EPIcys, respectively. Comparisons of the two CKD equations showed no significant difference in their predictive ability for mortality (difference in area under the curve p=0.46).

Conclusion: Despite reclassification of CKD stages, assessment of CKD using CKD-EPIcys did not improve prediction of mortality in older British men >70 years. Our data do not support the routine use of CKD-EPIcys for identifying CKD in the elderly British male population.