Assessment of Glomerular Filtration Rates by Cockcroft-Gault and Modification of Diet in Renal Disease Equations in a Cohort of Omani Patients

Objectives: Glomerular filtration rate (GFR) is the best index of renal function and is frequently assessed by corrected creatinine clearance (CCLcr). The limitations of CCLcr 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 CCLcr and estimated GFR (eGFR) by C-G, modified C-G and MDRD equations. Methods: From 2007 to 2011, 158 subjects were analysed for serum creatinine and CCLcr at Bowsher Polyclinic, Muscat, Oman. The C-G equation was used to obtain eGFRC-G which was adjusted to body surface area (BSA) to obtain eGFRmC-G, and the MDRD equation was used to obtain eGFRMDRD. The eGFRMDRD, eGFRmC-G and eGFRC-G were then compared to CCLcr. Results: The eGFRMDRD, eGFRmC-G and eGFRC-G significantly correlated with CCLcr, with a slightly stronger correlation with eGFRMDRD (r = 0.701, 0.658 and 0.605, respectively). A receiver operating characteristic curve analysis showed that the diagnostic accuracy of eGFRMDRD for diagnosing chronic kidney disease (CKD) was higher than that of eGFRmC-G, which in turn was higher than that of eGFRC-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). Conclusion: C-G and MDRD equations can be an alternative to the CCLcr 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