Implication of using estimated glomerular filtration rate (GFR) in a multi ethnic population of diabetes patients in general practice

Aim: To estimate the prevalence of chronic kidney disease (CKD) among diabetes patients in New Zealand, using estimated Glomerular filtration rate (eGFR); to measure the agreement between the Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault (CG) equations in identifying CKD among Europeans and Māonori; to review the metabolic control and treatment in patients with evidence of CKD. Method: Diabetes patients were identified though general practice records of diagnosis codes, diabetes annual reviews, prescriptions and laboratory results. The MDRD and CG equations were used to calculate the eGFR. Agreement between the two equations was expressed using Kappa statistics and was tested using McNemar's chi-square test. Logistic regression model was used to identify the predictors of CKD (eGFR<60 ml/min/1.73m2). Results: Overall prevalence of CKD among diabetes patients was 19.5% (MDRD) and 23.5% (CG). Maori were significantly more likely to have CKD [Odds-ratio 1.8(1.2-2.8)]. There were significant differences between the MDRD and the CG equations in identifying patients with CKD. While CG equation identifies more European of both genders, more Maori females were identified by MDRD. Conclusion: Patients with decreased eGFR who do not have proteinuria or microalbuminuria might benefit from more intensive management of blood pressure. MDRD equation may be overestimating CKD among Maori females. Each ethnic subpopulation may need to be validated separately, and by gender.