Validation test of a urinary concentrator used for urinary protein electrophoresis

Abstract

Introduction: In clinical laboratory, urinary protein electrophoresis is used to define the excretion profile as an indicator of kidney damage in patients with proteinuria and to detect monoclonal components present in urine in patients with myeloma and amyloidosis. Prior to electrophoresis, urine must be concentrated by means of commercially available devices, whose performance must be validated according to the requirements of each laboratory. Objective: To validate a Sartorius Vivaspin6 centrifugal-type concentrator with a cut-off molecular weight of 10 kDa. Materials and methods: Eleven urine samples with protein content that ranged from physiological (200 mg / 24 h) to nephrotic were selected. Samples were concentrated for 30 minutes at 3500 RPM with an initial volume of 6 ml and then each concentrate was electrophoresed. In a second stage, three mixtures were prepared with concentrations of 25, 50 and 100 mg/dl of the kappa light chain obtained from a patient with known myelomatous-type proteinuria.
These were concentrated with the same protocol. Electrophoresis was performed by manual method in cellulose acetate, staining with amido black. Results: The concentrates ranged between 10 and 60x and the protein fractions of clinical interest were visualized in the electrophoresis. Conclusions: The proposed requirement was met. To standardize it, it was decided to work at variable times, leading to a final volume between 100 and 200 μl and concentration between 30 and 60x.