Comparison of Glomerular Filtration Rate Estimated by Three Methods in a Pakistani Community Cohort

Background: Estimated glomerular filtration rate (eGFR) has always been considered a better and more accurate method to assess kidney function as compared to serum creatinine. Various equations such as the Cockroft-Gault equation corrected for surface area (CG-CRTD), the four-variable Modification of Diet in Renal Disease equation (MDRD) and 2009 Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI) have been derived to estimate GFR. In the South Asian region, the CKD-EPI equation has not been validated or compared with other equations. This study compares eGFR in a Pakistani community cohort calculated by all three equations. Results: Serum creatinine was measured using Kinetic Colorimetric Assay in alkaline medium for 461 individuals age 15 and above. Less than half of the participants (47% by CG-CRTD, 40% by MDRD, 52% by CKD-EPI) had eGFR ³90 ml/min per 1.73 m2 and for participants with eGFR ³120 ml/min per 1.73 m2 , the percentages were even lower (15%, 12%, and 22% respectively). All the equations were linearly associated with each other, but the error estimation depicted that majority of the individual differences were ≥5 and ≤-5, and very few were within ±1 indicating less degree of agreement between the formulas. Age was significantly but negatively correlated with all the three formulas in their classification of patients as per eGFR Conclusion: Our study found that the values of estimated GFR are on lower side for Pakistanis as compared to the western population. The equations available for estimation of GFR even though associated linearly with each other have significant individual differences. Thirdly, using eGFR to classify CKD should have a better consideration of physiological age-related decline in GFR. All of these findings necessitate having an adequately funded randomized study measuring true GFR of this population and at the same time validating eGFR equations to find the normal GFR ranges of South Asians.