Kidney function estimated with the different formulas in centenarians
Wieczorowska-Tobis K, Niemir ZI, Guzik P, Mossakowska M

Purpose: There are growing doubts about the accuracy of Cockcroft-Gault formula (CG) used for the estimation of creatinine clearance, especially in elderly. Recently, the authors of the multicenter trial of the Modification of Diet in Renal Diseases (MDRD) have proposed a new equation. Moreover, Baracskay et al. (B), proposed the special formula for the estimation of kidney function (KF) in elderly. The aim of our study was to compare the results of KF calculated with these three formulas in centenarians. 
Material and methods: The study involved 50 centenarian subjects aged 100-111 years (41 females and 9 males) who participated in Polish Centenarians Program. In all of them KF was estimated with the CG, B and MDRD formulas. 
Results: In the whole population examined, the mean KF according to CG was lower in comparison to both others (p<0.001 vs both B and MDRD). Also, in females CG results were the lowest (p<0.001 vs both B and MDRD). In contrast, KF calculated according to CG and B did not differ in males. The results of the MDRD formula significantly exceeded the two others also in males (p<0.001 vs CG and B). No impact of gender on the obtained results could be found when CG and MDRD were used. However, according to B, the mean values for females were higher (p<0.01). 
Conclusions: KF calculated with the CG, B and MDRD formulas significantly differed in the centenarians examined. Thus, further studies, which include a reference standard, are necessary to answer the question which of these mathematical formulas is the most reliable for the calculation of KF in the elderly. 

Key words:   centenarians, kidney function, mathematical formulas.