Estimated glomerular filtration rate equations and their impact on risk prediction - a tertiary centre experience

Abstract Background In 2021 use of the Kidney Failure Risk Equation (KFRE) was recommended by NICE to guide referrals from primary care. KFRE was developed using the CKD-EPI (2009) equation. We assessed the potential impact of use of multiple different estimating equations for GFR upon KRFE referral thresholds. Methods We searched our local research collection for patients with paired uPCR, serum creatinine and serum cystatin C. The proportions of patients meeting the five-year KFRE > 5% and two-year KFRE > 20% thresholds were then determined, both within and across specific CKD aetiologies. Results Moving to updated equations meant fewer women met the threshold for referral from primary to secondary care. For men an increase in the number crossing the same threshold was seen using CKD-EPI (2009) and CKD-EPI (2021) (combined), with a fall seen using CKD-EPI (2021) (creatinine). With regards to planning for dialysis or transplantation a fall was once again seen when using updated equations, excepting in men when the CKD-EPI (2009) and CKD-EPI (2021) (combined) equations were used. A fall was seen within CKD subgroups crossing both thresholds when using CKD-EPI (2021). Use of CKD-EPI (2021) (combined) and CKD EPI (2009) resulted in more mixed results, with both increases and reductions seen at each referral threshold across CKD subgroups. Conclusions There is likely to be an impact upon referrals made from primary to secondary care following adoption of any new estimating equation for GFR. Consensus around standardization of equations for GFR estimation and their use in risk stratification calculators is needed in the future.