Assessment of prostate-specific antigen (PSA) stability in urine during immunochemical studies

Relevance. The increasing incidence and late diagnosis of prostate cancer make scientists search for new ways to diagnose this disease, including by analyzing prostate specific antigen (PSA) in various biological materials. Objective. The aim of this study is to compare the stability of PSA concentration in samples of blood serum and urine under different storage conditions. Materials and methods. PSA concentration was studied in parallel samples of blood serum and urine from men stored at different temperature conditions: at room temperature, at 4 °C, and in a freezer. PSA concentration was determined by enzyme immunoassay using PSA-IFA-BEST test system (T-8458) manufactured by JSC Vector-Best (Russia). Results. The stability of PSA content differed significantly between the biological fluids. PSA in urine showed lower stability compared to blood serum. At room temperature, a noticeable decrease in PSA levels (more than 5% from the initial level) was observed by day 2; at 4 °C, this occurred in all samples by day 3; and at –20 °C, after three weeks of storage. Discussion. The lower stability of PSA in urine limits the storage time of this biological material during which correct test results can be obtained. Fresh urine should be tested within an hour after collection, and if storage is necessary, urine should be frozen and stored at –20 °C for no more than 3 weeks.