Longitudinal assessment of measured and estimated glomerular filtration-rate in autosomal dominant polycystic kidney disease: Real practice experience.

Background: Equations for estimation glomerular filtration rate (eGFR) have been associated with poor clinical performance and their clinical accuracy and reliability have been called into question.

Aim: To assess the longitudinal changes in measured glomerular filtration rate (mGFR) in patients with autosomal dominant polycystic kidney disease (ADPKD).

Methods: Analysis of an ambispective data base conducted on consecutive patients diagnosed with ADPKD. The mGFR was assessed by iohexol clearance; while eGFR was calculated by three different formulas: (1) The chronic kidney disease epidemiology collaboration (CKD-EPI); (2) Modification of diet in renal disease (MDRD); and (3) The 24-hour urine creatinine clearance (CrCl). The primary end-points were the mean change in mGFR between the baseline and final visit, as well as the comparison of the mean change in mGFR with the change estimated by the different formulas.

Results: Thirty-seven patients were included in the study. As compared to baseline, month-6 mGFR was significantly decrease by -4.4 mL/minute ± 10.3 mL/minute (P = 0.0132). However, the CKD-EPI, MDRD, and CrCl formulas underestimated this change by 48.3%, 89.0%, and 45.8% respectively, though none of these differences reached statistical significance (P = 0.3647; P = 0.0505; and P = 0.736, respectively). The discrepancies between measured and estimated glomerular filtration rate values, as evaluated by CKD-EPI (r = 0.29, P = 0.086); MDRD (r = 0.19, P = 0.272); and CrCl (r = 0.09, P = 0.683), were not correlated with baseline mGFR values.

Conclusion: This study indicated that eGFR inaccurately reflects the decline in mGFR and cannot reliably track changes over time. This poses significant challenges for clinical decision-making, particularly in treatment strategies.