Estimation of glomerular filtration rate in patients with systemic lupus erythematosus

The objective of this study was to compare the limit of agreement of creatinine clearance (CrCl) estimated by different equations with the CrCl measured by 24-hour urine collection in Hong Kong Chinese patients with systemic lupus erythematosus (SLE). Forty-three SLE patients with mild to moderate renal impairment (serum creatinine concentration 80 mol/L to 300 mol/L for females; and 106 mol/L to 300 mol/L for males) and not requiring renal replacement therapy were assessed. The estimated clearances were calculated by the Cockcroft-Gault (CG) equation, the Modification of Diet in Renal Disease (MDRD) study equation and the abbreviated MDRD (aMDRD) study equation. The estimated clearances were compared against the measured CrCl by 24- hour urine collection for their limit of agreement. Forty-three patients with mean (SD) age of 41.6 (8.4) years were assessed. As compared to the measured CrCl in patients with SLE, the clearances by CG equation, MDRD and aMDRD equations predicted a mean difference of 0.8% (95% confidence interval, 43.9-42.3%); 8.6% (95% CI, 24.3-7.2%) and 4.7% (95% CI, 21.4-12%), respectively. There is a tendency for the MDRD and aMDRD study equations to underestimate CrCl. The MDRD and aMDRD study equations have better predictive value than the CG equation.