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Clin Chim Acta. 2009 Dec;410(1-2):90-2. doi: 10.1016/j.cca.2009.09.018. Epub 2009 Sep 18.

Pre-analytical and analytical considerations for the determination of plasma renin activity.

Author information

1
Department of Nuclear Medicine, University Hospital and University of Bordeaux, France. julie.brossaud@u-bordeaux2.fr

Abstract

BACKGROUND:

Primary hyperaldosteronism diagnosis is helped by assaying renin concentrations either by immunodetection (active renin) or by enzymatic reaction followed by angiotensin I immunoassay (plasma renin activity). We investigated the impact of pre-analytical and analytical conditions on a PRA assay.

METHODS:

PRA was assayed using a commercial kit. Firstly, a retrospective analysis of PRA results from 1yr was performed. Secondly, the impact of pre-analytical temperature conveyance/storage of samples was tested (4 and 25 degrees C). Thirdly, 2 durations of enzymatic reaction 1.5 and 18h were tested.

RESULTS:

Retrospectively, 9.5% samples displayed elevated "blanks": calculating PRA with or without "blank" subtraction elicited a difference of >10% in 1/3 samples. There was a significant decrease of PRA values in samples left at 25 degrees C vs 4 degrees C (50% "blank" increase). Finally, the longer the enzymatic reaction (1.5 vs 18h), the higher the production of angiotensin I and the better the PRA assay sensitivity.

CONCLUSION:

We propose a 2 step procedure: a brief 1.5h enzymatic reaction time followed by a prolonged reaction (18h) only if PRA is <0.2ng mL(-1) h(-1). We would recommend performing "blank" samples for the brief enzymatic reaction time. Finally, conveyance/storage temperature does modify PRA results albeit in our hands this had little clinical impact.

PMID:
19766575
DOI:
10.1016/j.cca.2009.09.018
[Indexed for MEDLINE]
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