Comparison of four commercial urinary albumin (microalbumin) methods: implications for detecting diabetic nephropathy using random urine specimens.

The results of four urinary albumin methods used to identify patients with early diabetic renal disease were compared using random urine samples from healthy and diabetic patients. These methods were the Beckman Array and Behring BNAI immunonephelometric methods, the Dade aca particle-enhanced turbidimetric inhibition immunoassay method, and the INCSTAR SPQ immunoturbidimetric method. The albumin/creatinine ratio reference interval was found to be 2-20 mg albumin/g creatinine (mg/g) for the Array and 3.5-27.5 mg/g for the aca method. All four methods were compared using urines from a group of diabetic and nondiabetic patients. The BNAI, SPQ and Array methods compared well with one another while the aca demonstrated a positive bias of almost 60% at the 30 mg/g and 300 mg/g levels with certain lots of reagent and calibrator. Calibrator cross-over experiments demonstrated that some of the positive bias of the aca method could be accounted for by calibrator differences.