Formula-based estimates of the GFR: equations variable and uncertain.

Regarding the prevalence of chronic kidney disease in the population, estimation of glomerular filtration rate is of importance. Creatinine-based formulas are thus useful as the first step of a prevention strategy. Several creatinine-based formulas have been published. Among these, the Cockcroft-Gault formula and the Modification of Diet in Renal Disease (MDRD) study equation are the most used by physicians. The latter may be automatically reported by laboratories and has thus great success. However, these formulas have limitations. First, the MDRD formulas are not applicable to all populations, notably the healthy one and the patients with abnormal weight (anorectic or obese). Second, we evoke the limitations in the precision of the formulas linked to analytical aspects. Indeed, these analytical limitations remain significant even if they are improved by creatinine standardization. Lastly, we briefly mention the potential impact of these limitations on the epidemiology and the staging of chronic kidney disease.