Comparison of combined urea and creatinine clearance and prediction equations as measures of residual renal function when GFR is low

Abstract

The 4-variable MDRD formula is currently the best available prediction equation for GFR, but will nevertheless over estimate residual renal function when this is significantly impaired in up to 36% cases. Collection of 24 h urine samples may still have a role in the assessment of patients with stages 4 and 5 CKD.