Obtaining suitable results unaffected by preanalytical factors is crucial for laboratory test results. Measurement of parathyroid hormone (PTH) is essential in the evaluation and management of calcium metabolism disorders. The aim of the present study is to evaluate the effects of preanalytical factors such as sample type, storage time and temperature on PTH measurement in the same protocol. Blood samples were collected from 30 healthy volunteers into Serum Separator Tubes (SST), Barricor plasma tubes and EDTA aprotinine tubes. Serum and plasma were analysed immediately after collection simultaneously in the same batch and stored at room temperature RT (250C) and at (40C) for 24 and 48 hours until reanalysis for PTH on DXI800 autoanalyser (Beckman Coulter, USA). Changes in different tubes under different storage conditions were recorded and compared to each other. Clinical decision levels were estimated using analytical desirable bias and reference change value(RCV). No difference was found between tubes in terms of intact PTH levels. From a statistical standpoint, intact PTH level was no longer stable after storage for 24, and 48, hours at 4 C° and 25 C° in both serum tubes and barricor tubes. However, the variations especially in barricor tubes were under analytical desirable bias limits at 4 C0 for 24 hours (-10.48%), and 48 hours (-15.42%) hours and the changes were also not clinically significant. Our results have shown that Barricor tubes are stable at 4 C° up to 48 hours.The stability of the measurements were both analytically and clinically acceptable.
Key words: Barricor tube; Preanalytical phase; Parathyroid hormone; Reference change value; Storage conditons; Serum separator tube
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