Application of GFR estimation equations in elderly patients with measured GFR below 60 mL/min/1.73 m.

Background: Estimated glomerular filtration rate (eGFR) equations can be inaccurate when applied to elderly patients. Newly, the full-age-spectrum (FAS) equation was developed for use in elderly patients.

Aim: We compared the available eGFR equations in elderly Chinese patients with mGFRs < 60 mL/min/1.73 m.

Methods: Measured glomerular filtration rates (mGFRs) were obtained using Tc-DTPA (diethylene-triamine-pentaacetic acid) scans, 220 patients ≥ 80 years with mGFRs < 60 mL/min/1.73 m were enrolled. Serum creatinine (SCr) levels were measured simultaneously, and eGFRs based on SCr were calculated using four formulas: the modification of diet in renal disease (MDRD), chronic kidney disease epidemiology collaboration (CKD-EPI-SCr), Berlin initiative study (BIS1), and the FAS-SCr equations.

Results: All the equations tended to overestimate GFR. The FAS-SCr equation provided the least bias (1.84), the highest proportion of eGFR within 30% of mGFR (P30, 72.7%), the bias and P30 of the BIS1 equation were 3.45 and 72.3%, respectively. In patients with mGFRs of 30-60 mL/min/1.73 m, the BIS1 and FAS-SCr equations demonstrated better performances than the MDRD and CKD-EPI-SCr equations. While in patients with mGFR < 30 mL/min/1.73 m, the accuracy of all equations was poor.

Discussion: In older patients with mGFRs of 30-60 mL/min/1.73 m, the BIS1 and the FAS-SCr equations exhibited good performance, none of the equations based on SCr were suitable for older subjects with mGFRs < 30 mL/min/1.73 m.

Conclusions: The BIS1 and FAS-SCr equations may be optimal for older patients with moderately reduced kidney function.