Impact of Adoption of European Kidney Consortium Equation (EKFC) on CKD Prevalence and CKD Staging in Older Irish Adults

Background The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation tends to overestimate glomerular filtration rate (GFR) and has limitation in younger and older age groups, while the European Kidney Function Consortium (EKFC) full-age spectrum (FAS) correct for these problems and provide better performance in estimating GFR. We compared the 2017 EKFC- FAS(Scr-CysC) equation with 2012 CKD-EPI(Scr-CysC) for estimating CKD prevalence and staging in a national representative sample of older Irish adults. Methods We utilised data from The Irish Longitudinal Study on Ageing (2009-2011), for participants aged 50 to 79 years with complete measurement of serum creatinine (Scr) and Cystatin-C (CysC). Using 2017 EKFC- FAS(Scr-CysC) and 2012 CKD-EPI(Scr-CysC), equations eGFR was calculated. CKD was defined as eGFR below 60 ml/min/1.73 m². Median eGFR, CKD prevalence, concordance correlation coefficient (CCC), and impact of EKFC equation on GFR category reclassification was examined. Results A total of 5,092 participants (53.3% women), median age 61 years were included. CKD prevalence varied significantly from 10.8% (9.9% – 11.8%) using 2021 CKD-EPI (Scr -CysC) to 16.7 % (15.5-17.9%) with the 2017 EKFC- FAS(Scr-CysC) equation. The corresponding numbers of CKD increased from 114,867 to 176,439 individuals respectively. The median eGFR for 2021 CKD-EPI (Scr -CysC) was 82.1 ml/min/1.73m2 and 2017 EKFC- FAS(Scr-CysC) was 74.5 ml/min/1.73m2, P<0.001). The net reclassification was 23.1 % based on 2017 EKFC- FAS (Scr-CysC) equation compared to CKD-EPI 2012 (Scr -CysC) and was towards more worsening CKD stage. The CCC between 2012 CKD-EPI(Scr-CysC) and 2017 EKFC- FAS(Scr-CysC) was 0.88 (95% CI, 0.88-0.89). Conclusion CKD prevalence varies according to eGFR equation with substantially higher numbers of CKD predicted by the European Kidney Function Consortium than CKD-EPI equations. This has direct implications on healthcare planning, resource allocation, and rates of referral to specialist nephrology services in Ireland.