Received on September 29, 2008
Accepted on January 22, 2009

Reviews

Activity Assays and Immunoassays for Plasma Renin and Prorenin: Information Provided and Precautions Necessary for Accurate Measurement

¹ St. Vincent's Institute of Medical Research and Department of Medicine, University of Melbourne, St. Vincent's Hospital, Fitzroy, Victoria, Australia
² Division of Angiology and Hypertension, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland
³ Endocrine Hypertension Research Centre, University of Queensland School of Medicine, Greenslopes and Princess Alexandra Hospitals, Brisbane, Queensland, Australia
⁴ Division of Pharmacology, Vascular and Metabolic Diseases, Department of Internal Medicine, Erasmus MC, Rotterdam, the Netherlands
⁵ Department of Internal Medicine, Hypertension Unit, Ospedale San Giuseppe and Centro Fisiologia Clinica e Ipertensione, University of Milan, Milan, Italy
⁶ Biolab, Department of Clinical Physiology and Nuclear Medicine, Glostrup University Hospital, Glostrup, Denmark
⁷ Faculté de Médecine Paris Descartes, University Paris 5, Paris, France

^* To whom correspondence should be addressed. E-mail: dcampbell{at}svi.edu.au.

BACKGROUND: Measurement of plasma renin is important for the clinical assessment of hypertensive patients. The most common methods for measuring plasma renin are the plasma renin activity (PRA) assay and the renin immunoassay. The clinical application of renin inhibitor therapy has thrown into focus the differences in information provided by activity assays and immunoassays for renin and prorenin measurement and has drawn attention to the need for precautions to ensure their accurate measurement.

CONTENT: Renin activity assays and immunoassays provide related but different information. Whereas activity assays measure only active renin, immunoassays measure both active and inhibited renin. Particular care must be taken in the collection and processing of blood samples and in the performance of these assays to avoid errors in renin measurement. Both activity assays and immunoassays are susceptible to renin overestimation due to prorenin activation. In addition, activity assays performed with peptidase inhibitors may overestimate the degree of inhibition of PRA by renin inhibitor therapy. Moreover, immunoassays may overestimate the reactive increase in plasma renin concentration in response to renin inhibitor therapy, owing to the inhibitor promoting conversion of prorenin to an open conformation that is recognized by renin immunoassays.

CONCLUSIONS: The successful application of renin assays to patient care requires that the clinician and the clinical chemist understand the information provided by these assays and of the precautions necessary to ensure their accuracy.