20-year longitudinal follow-up of measured and estimated glomerular filtration rate in kidney transplant patients

BACKGROUND: The slopes of estimated glomerular filtration rate (eGFR) equations are used in the longitudinal follow-up of transplant patients. A 30% reduction in eGFR over 2 years is often used to predict the subsequent risk of mortality or end-stage renal disease. Whether, at the individual level, such changes in eGFR correspond to changes in measured GFR (mGFR) is actually unknown. METHODS: The performance of serum creatinine–based eGFR equations was compared with mGFR during the longitudinal follow-up of 20 years in a monocentric study of 417 transplanted patients. RESULTS: The accuracy within 30% for the eGFR equations varied between 70 and 75%. All eGFR equations showed a similar pattern, very like the mGFR time profiles. Individual changes (slopes) of mGFR or eGFR were predictive of graft loss in the next months or years, following the decline in GFR, with no evidence for a difference. However, although the tendency is the same as for mGFR, the percentage of transplant patients with a >30% GFR decrease in the last period before graft loss is significantly lower for eGFR than for mGFR, with discordant results from mGFR in ~25% of the cases. CONCLUSIONS: All eGFR equations showed similar trends as mGFR, but eGFR predictions may not be very useful at the individual patient level.