RESUMEN
Glomerular filtration rate [GFR] is the best index of renal function and is frequently assessed by corrected creatinine clearance [CCL[cr]]. The limitations of CCL[cr] have inspired researchers to derive easy formulas to estimate GFR, with Cockcroft-Gault [C-G] and the modification of diet in renal disease [MDRD] being the most widely used. This study aimed to evaluate the validity of these equations by finding the relation between CCL[cr] and estimated GFR [eGFR] by C-G, modified C-G and MDRD equations. From 2007 to 2011, 158 subjects were analysed for serum creatinine and CCL[cr] at Bowsher Polyclinic, Muscat, Oman. The C-G equation was used to obtain eGFR[C-G] which was adjusted to body surface area [BSA] to obtain eGFR[mC-G], and the MDRD equation was used to obtain eGFR[MDRD]. The eGFR[MDRD], eGFR[mC-G] and eGFR[C-G] were then compared to CCL[cr]. The eGFR[MDRD], eGFR[mC-G] and eGFR[C-G] significantly correlated with CCL[cr], with a slightly stronger correlation with eGFR[MDRD] [r = 0.701, 0.658 and 0.605, respectively]. A receiver operating characteristic curve analysis showed that the diagnostic accuracy of eGFR[MDRD] for diagnosing chronic kidney disease [CKD] was higher than that of eGFR[mC-G], which in turn was higher than that of eGFR[C-G] [area under the curve was 0.846, 0.831, and 0.791; cut-off limits were 61.9, 58.3 and 59.5, respectively]. C-G and MDRD equations can be an alternative to the CCL[cr] test for assessing GFR, thus avoiding the need for the cumbersome and expensive GFR test. The MDRD formula had greater validity than the C-G equation and the C-G equation validity was improved by an adjustment to BSA