Estimating ADPKD GFR: Which Method Is Best?
The CKD-EPI equation is the most reliable equation for measuring glomerular filtration rate (GFR) in patients with autosomal dominant polycystic kidney disease (ADPKD), regardless of CKD severity.
Previous research has not examined the reliability of various equations for estimating GFR in patients with ADPKD, or the influence of tolvaptan on the resulting estimates when GFR is calculated on the basis of insulin clearance, the researchers wrote.
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For their study, the researchers measured on-tolvaptan and baseline GFRs, calculated on the basis of insulin clearance, in 114 patients with ADPKD (stages 1-5), compared with eGFRs calculated according to 4 basic equations: the MDRD, CKD-EPI, and JSN-CKDI equations and the Cockcroft-Gault formula. The influence of tolvaptan and the inclusion of cystatin C on accuracy of the results were also measured. Accuracy of the resulting 7 equations was evaluated on the basis of the percentage of eGFR values within mGFR ± 30% (P30).
Regardless of CKD stage, P30s of the MDRD, CKD-EPI, and JSN-CKDI equations did not differ significantly between baseline and on-tolvaptan. In CKD 1-2 patients, P30 of the CKD-EPI equation was 100.0%, regardless of tolvaptan status. In CKD 3-5 patients, P30s of the MDRD, CKD-EPI, and JSN-CKDI equations were similar.
For all 4 equations, regression coefficients and intercepts did not differ significantly between baseline and on-tolvaptan values, but accuracy of the Cockcroft-Gault formula was inferior to the other 3 equations. Inclusion of serum cystatin C reduced accuracy.
“The CKD-EPI equation is most reliable, regardless of the severity of CKD. Tolvaptain intake has minimal influence and cystatin C incorporation does not improve accuracy.”
—Michael Potts
Reference:
Yamaguchi T, Higashihara E, Okegawa T, et al. Optimal equation for estimation of glomerular filtration rate in autosomal dominant polycystic kidney disease: influence of tolvaptan [published online May 22, 2018]. Clin Exp Nephrol. doi: 10.1007/s10157-018-1574-2.