Performance Verification of Alternative Quality Control Materials for Urine Albumin Assessment

Accurate detection of urine albumin is important for evaluating the progression of diabetic kidney disease. However, two levels of daily quality control may not be practically feasible in some small clinical laboratories owing to a small number of patient samples and high costs. We aimed to prepare homemade quality control material (HQM) to measure urine albumin and then verify its performance.

Normal saline solution and fresh mixed urine samples from five donors with serious kidney disease were used to prepare two levels of HQM (HQM1 and HQM2). Anhydrous ethylene glycol and sodium azide were used as antifreeze and as a preservative, respectively.

Before being separated into Eppendorf tubes, 20 tests for HQM1 and HQM2 were performed, resulting in mean ± SD of 19.52 ± 0.91 mg/L and 105.28 ± 3.71 mg/L, respectively. After having been divided, the vial-to-vial variations of HQM1 and HQM2 were small (4.93% and 3.70%, respectively). The stability of HQM1 and HQM2 stored at 2 - 8°C was about 2 months and 80 days, respectively, and when stored at -20°C, remained stable for more than 8 months. After 1 - 8 months of cryopreservation at -20°C, once opened, the HQM in every Eppendorf tube could be kept for at least five days (CV < 6.1%).

Our HQM stored at -20°C remained stable for a long time, and so could be considered as an alternative to standard QMs in the clinical laboratory.