engleski

Preanalytical handling in active plasma renin concentration measurement

Background: Renin, a member of Renin-Angiotensin-Aldosterone System, is constitutively produced as an inactive precursor prorenin. It is well known that cryoactivation of prorenin may occur in low temperature range (2–8°C), giving false positive active plasma renin concentration (PRC). Thus, it is recommended to rapidly freeze and thaw samples avoiding low temperature. The aim of this study was to compare two preanalytical procedures in active PRC measurement in thawed plasma specimens. Methods: 30 EDTA plasma samples, with PRC ranging from 0.8 to 128 ng/mL were split into two aliquots, rapidly frozen and stored (20 days, -25°C). Split aliquots were processed on the same day by either rapidly thawing (37 °C, water bath) or left to thaw at the room temperature (RT, 25 °C) prior the analysis. PRC was determined on the same microplate with DRG Renin ELISA enzyme immunoassay (intra-assay CV = 4.5%). PRCs obtained by the two preanalytical procedures were compared by Bland and Altman analysis. The concordance between the two storage procedures was checked by interrater agreement (kappa). Results: Bland and Altman plot revealed an average positive bias of 11.9% (95% CI: 7.1-16.7) in RT-thawed aliquots compared to PRC in rapidly thawed aliquots. However, a very good agreement between the two preanalytical procedures in classifying patients as low, normal or high, according to the reference interval was observed (weighted kappa = 0.919). Conclusion: Despite a mild positive bias, thawing frozen plasma samples at room temperature is not-inferior to water-bath thawing procedure for active plasma renin concentration measurement, in providing clinically reliable information.

renin, plasma, freezing, thawing

nije evidentirano