Proteinuria Determined by Automated Analyzer

A rapid, accurate, and cost-effective method for their detection of protein in urine has been developed for the autoanalyzer.

The method is a two-reagent system consists of a buffer solution and surfactants, and a second one consists of a dye solution of Erythrosin B being added to a urine sample, and the dye bound protein is measured by a spectrophotometer.

At the Juntendo University (Tokyo, Japan) nephrologists enrolled 70 outpatients who were screened for proteinuria by the dipstick test. Spot urine samples from the patients and 79 healthy volunteers were examined. Urine samples were stored at -80 °C. A solution containing a buffer agent with a pH 2.3 and surfactants and a solution of Erythrosin B are added to each urine sample. After letting the mixture stand for five minutes at 37 °C, the dye-bound protein is measured by a spectrophotometer at 546 nm using an automated analyzer.

The calibration curve was linear with human serum albumin concentration in the range of 2.4-200 mg/L. The detection limit, 2.4 mg/L was superior to conventional dye-binding methods by one order of magnitude and comparable to the turbidimetric immunoassay (TIA), which is quite expensive. There was an excellent correlation between the results given by the Erythrosin B (Wako Pure Chemical Industries Ltd., Tokyo, Japan) method and those by the TIA.

The authors concluded that the method is equal to the dipstick test in terms of time and cost savings. The reaction was completed within 5 minutes at 37 °C after mixing the test solution, and could be coupled with the 7170S automated analyzer (Hitachi, Tokyo, Japan) for rapid detection. The method was capable of determining actual samples without being influenced by foreign substances in urine such as urea, creatinine, and glucose. This method is sufficiently sensitive for the detection of trace proteinuria in early-stage of chronic kidney disease, and is directly applicable to actual samples. The study was published in the July 2012 issue of the journal Clinica Chimica Acta.

Related Links:
Juntendo University
Wako Pure Chemical Industries Ltd.
Hitachi