Agreement of Different Immunoassays for Urinary Albumin Measurement

Diagnosis of diabetic nephropathy (DN) is based on measurements of urinary albumin (UALB) by a sensitive analytical method with sufficient analytical precision (CV <15%) to detect changes in UALB concentration(1)(2)(3). We evaluated the comparative diagnostic accuracies of 4 UALB assays for DN.We used urine samples from 98 diabetic outpatients. UALB was measured by 4 immunoturbidimetric (IT) assays: the Urine Pack Immuno method (Bayer) as implemented on a Roche Cobas Mira Plus (method A), Malb Aptec Diagnostic (BioSys) (method B), Albumin Tina-quant (Roche) (method C), and Microalbumin (Randox) (method D). Methods B, C, and D were implemented on a Hitachi 917 analyzer (Roche). Method A was considered as the reference standard (comparison method) because it had been used in our laboratory since 1996 and validated in previous studies(2)(4)(5). Total urinary protein was measured before UALB, and the U/CSF Protein assay (Roche) on the Hitachi 917 analyzer (Roche) was used to estimate the contribution (%) of albumin to total protein for each sample(5). Based on this estimate, we prediluted samples to allow …