ABSTRACT
This study aimed to determine the correlation between the GFR estimates from plasma-derived formulas (Cockroft-Gault, MDRD, AASK, Nankivell) and the GFR estimates from the clinically conventional 24-hour creatinine clearance method and identify which formula could become a potential substitute for the creatinine clearance method. Another aim was to propose adjusted plasma-derived formulae that apply to the Filipino populationOne hundred and nine volunteers were asked to undergo 24-hour urine collection and blood extraction. The urine and blood samples were then examined by the PGH laboratories, where serum BUN. serum albumin, and serum and urine creatinine were determined. These values, in addition to age, weight, sex, and body surface area, were used to calculate GFR via the Cockroft-Gault, MDRD7, AASK, and Nankivell formulas, as well as via the creatinine clearance method. Subjects whose calculated total creatinine was lower than normal were excluded. A total of 44 subjects were included in the data analysisRegressional analysis was used to measure correlation. The null hypothesis is a=alpha and b=beta or the y-intercept and slope of the formulas and creatinine clearance are equal. A paired t-test with 42 degrees of freedom was used to calculate significance with the critical values t -2.0289 and t2.0189. Among the formulas evaluated, both the AASK formula (r=0.8836, a=0.0056, b=-0.4994) and the MDRD formula for African-Americans (r=0.8589, a=2.4514, b=-0.5998) consistently overestimate the creatinine clearance values. However, the overestimation of the AASK formula is statistically insignificant, while that of the MDRD for African Americans is significant. However, upon the addition of -21.3 for MDRD-African American and -12.99 for AASK equations, respectively, yielded a closer approximation of creatinine clearance values in the sample population (MDRD r=0.8545, a=-0.0004, b=0.1995; AASK: r=0.8589, a=-0.0001 , b=-0.5998), thus formula effectiveness studies on other populations are recommended. Both the Nankivell formula (r=0.8462, a=4.3836, b=-6.2810) and standard MDRD (r=0.8589, a=2.4514, b=-2.6643) formula do not closely correlate with creatinine clearance. The Cockroft-Gault equation (r=0.8836, a=0.0056, b=-0.4994) shows the highest correlation, unadjusted, with corrected creatinine clearance in the selected population and could be recommended as a substitute for creatinine clearance. (Author)