Background: Because no systematic study on the comparison of the stability of plasma renin activity (PRA) and renin concentration (REN) under different preanalytical conditions has been reported, we examined the impact of several sampling and storage conditions.
Methods: Blood samples were collected into prechilled tubes and into tubes at room temperature and processed within 30 min or kept at room temperature or at 0-5 degrees C for 2 h. The stability of PRA and REN after storage at - 20 degrees C was also analysed. PRA and REN were determined with radioimmunoassay (DiaSorin) and chemiluminescent immunometric method (LIAISON, DiaSorin), respectively.
Results: When blood samples were kept at room temperature for 2 h, the PRA and REN decreased significantly (p < 0.001), but both remained unchanged if samples were placed at 0-5 degrees C for the same time period. The REN was significantly higher in samples collected in prechilled tubes and refrigerated within 30 min at 0-5 degrees C compared to samples processed at room temperature (p < 0.05). During storage at -20 degrees C for 7 weeks the PRA decreased by 31.9 +/- 4.7%, while the change in REN remained below 5%.
Conclusion: Different sampling and storage conditions differentially influence the PRA and REN, which makes it necessary to apply well-defined preanalytical procedures for PRA and REN measurements.