Glomerular filtration rate estimation: performance of serum cystatin C-based prediction equations

Serum creatinine measurement is a mainstay in the routine laboratory evaluation of renal function, despite of having several disadvantages. Cystatin C, on the other hand, suffers less influence of gender and muscle mass and has been proposed as a more sensitive marker for glomerular filtration rate. However, serum endogenous markers should not be used alone to assess glomerular filtration rate. Creatinine-based equations such as the modification of diet in renal disease (MDRD) and Cockcroft-Gault are widely used despite their limitations. A large number of cystatin C-based prediction equations were developed in recent years, in diverse populations, with different laboratory assays and methods. Several studies demonstrated that cystatin C-based equations are reliable markers of glomerular filtration rate and can be used for diagnosis, evaluation and follow-up of kidney disease. They are simpler than creatinine-based equations and have at least the same accuracy and precision for glomerular filtration rate estimation. In conclusion, diabetes mellitus, cystic fibrosis, kidney transplantation, HIV-infection, and cirrhosis are clinical situations where cystatin C-based equations can be useful. Extremes of age such as childhood and advanced age have also been evaluated with favorable results.