The estimation of kidney function with different formulas in overall population

Background. The limitations of the laboratory evaluations of kidney function (KF) are well recognized. Therefore, in clinical practice, various mathematical formulas are applied for the bedside estimation of KF. Aim. The aim of this study was to compare the calculated KF function derived from two different formulas i.e. the Cockcroft-Gault (CG) formula and the shorten version of Modification of Diet in Renal Disease (MDRD) formula, in patients at different ages. Material and methods. The study involved three groups of patients at different ages. In all of them serum creatinine was within the reference values. Group A was composed of 40 healthy subjects aged 20-35 years (25.6  4.2 years), group B of 50 elderly subjects at 65-92 years of age (mean age: 74.8  8.2 years), and group C of 50 centenarians aged 100-111 (mean age: 101.7  2.0 years). In all subjects, KF (ml/min/1.73 m2) was estimated based on the CG and the shortened version of the MDRD formula (MDRDs). Results. The comparison of the results obtained with both formulas showed that those calculated using CG were higher in group A (96.0  22.1 vs. 82.0  23.0; p < 0.0001). In contrast, this equation gave significantly lower values in subjects from groups B and C (58.4  16.9 vs. 70.0  24.4; p < 0.0001 and 33.7  9.0 vs. 82.1  24.1, p < 0.0001, respectively). Conclusion. Thus, our results show that the CG formula gives significantly different results than the MDRDs equation and that the difference in the estimated KF is related to the age of the subjects. In the absence of an accurate reference method we cannot say which method gives more reliable results. Until such comparison is made, investigators should be aware of the differences existing. Geriatria 2013; 7: 137-141.