Accuracy of cystatin C-based estimates of glomerular filtration rate in kidney transplant recipients: a systematic review

As with creatinine, cystatin C can be incorporated into a formula to estimate the glomerular filtration rate (GFR). The overall performance of cystatin C-based equations in kidney transplantation is unclear with conflicting results between studies. Systematic review of adult kidney transplant recipients. Studies that reported mean bias (mean difference between the measured and estimated GFRs) or accuracy of the cystatin C-based GFR estimation equation (e.g. percentage of estimates within 30 of the measured GFR) against the measured GFR using renal or plasma clearance of contrast agents, radioisotopes or inulin were included. The search identified 10 studies that examined 14 different cystatin C-based estimating equations (n 5 equations evaluated in more than one study). The Le Bricon equation had the best performance with a bias that ranged from 6.4 to 2.8 mL/min/1.73 m(2); 85 (95 CI, 8288) of estimates were within 30 of the measured GFR. For the other equations, 6682 of estimates were within 30 of the measured GFR. For the modification of diet in renal disease (MDRD) equation, 68 (95 CI, 6572) of estimates were within 30 of the measured GFR. The cystatin C-based Le Bricon equation was the most accurate, and most of the cystatin C-based equations showed improvements in 30 and 50 accuracy compared with the creatinine-based MDRD equation. Cystatin C-based equations may offer an advantage over the MDRD equation in kidney transplant recipients. Estimating equations re-expressed with standardized cystatin C have been developed and their accuracy needs to be tested in the kidney transplant population.