The Influence Of Storage Conditions On The Plasma Renin Concentration And Plasma Aldosterone Concentration

Objective: To investigate the influence of plasma sample storage conditions of temperature and time on plasma renin concentration(PRC)and plasma aldosterone concentration(PAC).Methods: Plasma samples from 43 subjects were apportioned into 11 parts.One sample was used instantly to measure baseline PAC and PRC.The remaining samples were used for PRC and PAC measurements after storage at different temperature and time,at room temperature for 3 hours(h),6h,24 h;at 4°C for 3 h,6 h,24 h;at-20°C for 24 h,1 month,3 months;and at-80°C for 3 months.According to baseline PRC and PAC,the data from samples were divided into three tertiles of low,intermediate and high concentration for further analyses.Results: When samples were stored at room temperature for 24 h,PRC showed a significant decline(P<0.001,F=24.3),the decline was most significant in the intermediate and high tertiles after 6h(P<0.05).At 4°C the PRC level increased significantly at 24h(P<0.001,F=33.6).Further analysis showed that in the low and intermediate tertiles,PRC increased significantly at 3h(P<0.05),while in the high tertile a significant increase was seen at 24h(P=0.042).PRC was not significantly affected by temperature at-20°C and-80°C when samples were stored for 3 months.PAC was not influenced by temperature as no significant changes were seen when samples were stored at room temperature for 24 h,4°C for 24 h,-20°C for 3 months and-80°C for 3 months.Conclusion: PRC levels decrease when samples are stored at room temperature but an increase is seen when samples are stored at 4°C.The storage temperature does not influence PAC levels when samples are stored for 24 h.