Classification of chronic kidney disease by estimated glomerular filtration rate.

ABSTRACT

BACKGROUND: Serum creatinine concentration alone as a marker of kidney function is inadequate. Thus several equations for estimating glomerular filtration rate (eGFR) have been proposed within the last years. PATIENTS AND METHODS: In our study we compared three frequently used equations, the abbreviated modification of diet in renal disease (MDRD) formula, the extended MDRD formula and the recently proposed Mayo clinic equation in a large patient cohort. RESULTS: A total of 244 507 patients attending the Vienna General Hospital were evaluated for their kidney function and three equations for eGFR were compared. The median age of the patients was 51 years (ranging from 18.0 to 102.6 years) with 44.3% males (n = 108 527). We observed a significant increase of patients with eGFR classes four and five (according to Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines) with advanced age. Whereas approximately 1% of patients < 30 years presented with eGFR classes four and five (defined as eGFR < 30 mL min(-1) 1.73 m(-2)), this prevalence increased up to approximately 12% in patients at the age of 80 years or older. All three equations showed comparable results for eGFR classes four and five. The proportion of patients with mild to moderate impairment of kidney function is higher using both MDRD equations. CONCLUSIONS: The MDRD equations (particularly the abbreviated MDRD formula) result in considerably higher rates of eGFR classes two and three compared to the Mayo Clinic equation, while all three were comparable in classes four and five. This should be considered when eGFR is used in the diagnosis of chronic kidney disease.