Impaired selective renal filtration captured by eGFR(cysC)/eGFR(crea) ratio is associated with mortality in a population based cohort of older women

Deranged renal filtration of mid-sized (5–30 kDa) compared to smaller molecules (< 0.9 kDa) results in increased plasma levels of cystatin C (cysC) compared to creatinine resulting in a low eGFR(cysC)/eGFR(crea) ratio. A ratio below 0.6 or 0.7, is termed shrunken pore syndrome (SPS), which in patient based studies is associated with mortality. Reference values for eGFR(cysC)/eGFR(crea) ratio, the prevalence of SPS and the consequence of low eGFR(cysC)/eGFR(crea) ratio in the general, elderly population are unknown. 75-yr old women (n = 849) from the population-based OPRA cohort, followed for 10-years had eGFR calculated with CKD-EPI study equation, and eGFR(cysC)/eGFR(crea) ratio calculated. Mortality risk (HR [95% CI]) was estimated. Women with sarcopenia or on glucocorticoids were excluded. Almost 1 in 10 women (9%) had eGFR(cysC)/eGFR(crea) ratio < 0.6 at age 75 and this did not increase appreciably with age. Women with ratio < 0.6 had higher 10-yr mortality risk compared with ratios > 0.9 (HR(adj) 1.6 [95% CI 1.1–2.5]). In elderly women eGFR(cysC)/eGFR(crea) ratio < 0.6 is common and associated with increased mortality. Our results confirm patient-based findings, suggesting that identifying individuals with SPS may be clinically relevant to assessing mortality risk in the elderly.