[Evaluation of cystatin C-based glomerular filtration rate estimation formulae in chronic kidney disease]

To evaluate the validity of the simplified Modification of Diet in Renal Disease formula (MDRD) and the formulae based upon cystain C (Cys-C) for estimation of glomerular filtration rate (GFR) in Chinese patients with chronic kidney disease(CKD).

Serum creatinine and serum Cys-C were measured in 412 patients admitted in our hospital for determining the GFR by 99mTc-DTPA plasma clearance (sGFR) method between January 2008 to November 2009, and the difference, limits of agreement, precision and accuracy were calculated.

The estimated GFRs by all the formulae were significantly correlated to the sGFR (P<0.001). The Cys-C formulae 4 and 5 showed better consistence with sGFR than the other formulae. The Cys-C formulae 4 had greater diagnostic precision and accuracy for predicting the renal function. Compared with the other formulae, the Cys-C formulae 4 and 5 had better accuracy in stages 1 to 5 CKD (P<0.001). However, Bland-altman analysis demonstrated that only the Cys-C formulae 5 was well consistent with sGFR, for the limits of agreement was within the professional agreement of 60 ml x min(-1) x 1.73 m(-2).

Compared with the MDRD equation, the Cys-C formulae 4 and 5 has greater advantages in predicting the GFR in Chinese CKD patients. However, the limits of agreement of the formula should be improved by large-sample clinical trials.