Performance of the cockcroft-gault and modification of diet in renal disease equations compared to 24 hour creatinine clearance in Africans with chronic kidney disease at Kenyatta National Hospital

Abstract

The worldwide rise in the number of patients with chronic kidney disease and end-stage renal failure is threatening to reach epidemic proportions over the next decade. The Glomerular Filtration Rate (GFR) is traditionally considered the best overall index of kidney function in health and disease. Early detection of Chronic kidney disease (CKD) requires identification of individuals with reduced GFR.GFR has been estimated by measurement of Serum creatinine and creatinine excretion in a 24-h urine sample and computation of creatinine clearance. More than 25 different formulas have been derived for estimating GFR using plasma creatinine corrected for a combination of factors like gender, body size, race and age. The most widely used GFR prediction equations for adults are those proposed by Cockcroft and Gault and Modification of Dietin Renal disease equations i.e MDRD original study equation and more recently the MDRD abbreviated equation. These three equations have been validated in heterogeneous populations with various stages of CKD where they have demonstrated greater accuracy and consistency in estimating GFR by incorporating other known demographic and clinical variables other than serum creatinine alone. 2.2 Objectives To determine the performance of the Cockcroft-Gault and Modification Of Diet in Renal Disease equations(MDRD original and MDRD abbreviated) compared to the 24 hour Creatinine Clearance in Africans with chronic kidney disease at Kenyatta National Hospital. 2.3 Methods Across-sectional analysis of the measured 24hr creatinine clearance and estimated GFR using MDRD original,MDRD abbreviated and Cockcroft-Gault equations was carried out on 115 native Africans with CKD to assess the performance of these three commonly used formulas.Data collected included demographic variables,history of hypertension,history of diabetes, and serum biochemistryindices.Data was analysed using SPSS version 12.0 2 2.4 Outcome Measures Outcome measures included determining the GFR of the study population as calculated by Cockcroft-Gault equation and MDRD equation 7(original equation) and abbreviated MDRD equation(equation4) GFR estimating equations, comparing them with the 24 hour creatinine clearance.Indicators of the performances of these equations were derived from precision, bias and accuracy calculating equations. 2.5 Results Comparison was made between 24 hour creatinine clearance, Cockcroft & Gault and MDRD predictionequations on 115 African adult patients with CKD aged between 18 and 87 years old. Theirmean age was 48.1 years. Sixty-four males (55.7%) and 51 female (44.3%) subjects were studied.Thirty-nine (33.9%) were hypertensive patients,6 (5.2%) had diabetes, 36 (31.3%) had diabetes with hypertension and 34 patients (29.6%) were neither hypertensives nor diabetics. MDRD original equation had better correlation with 24 hour creatinine clearance as compared with Cockcroft-Gault and MDRD abbreviated equations. Statistical correlation was r = 0.815 for MDRDoriginalequation, r =0.794 for MDRD4 equations and r = 0.781 for Cockcroft-Gault equation.MDRD abbreviated equation had the least bias compared to MDRD original and Cockcroft-Gaultequations. The accuracy was greatest using MDRD original equation with 78.3% of calculated GFR values falling within 30% and 93% being within 50% of the measured 24hrcreatinine clearance. 2.6 Conclusion The3 GFR estimating equations MDRD original equation, MDRD abbreviated and Cockcroft- Gaultformulae had good agreement with the measured 24 hour creatinine clearance in stage 3, 4 and 5 of Chronic Kidney Disease. This means that the values of GFR as measured by creatinine clearance that classifies patients into stage 3, 4 and 5 of CKD will be in agreement with GFR values as calculated using the 3 GFR estimating equations in that they will also classify these same patients into CKD stage 3, 4 and 5.Patients with CKD stages 1 and 2 were not studied.