title: Activity assays and immunoassays for plasma Renin and prorenin: information provided and precautions necessary for accurate measurement.
abstract: 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.
  
  
  BACKGROUND
  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.
authors.affiliation: Department of Medicine, St Vincent's Institute of Medical Research, University of Melbourne, St Vincent's Hospital, Fitzroy, Victoria, Australia. dcampbell@svi.edu.au
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Campbell
authors.forename: Juerg
authors.initials: J
authors.lastname: Nussberger
authors.forename: Michael
authors.initials: M
authors.lastname: Stowasser
authors.forename: A H Jan
authors.initials: AH
authors.lastname: Danser
authors.forename: Alberto
authors.initials: A
authors.lastname: Morganti
authors.forename: Erik
authors.initials: E
authors.lastname: Frandsen
authors.forename: Joël
authors.initials: J
authors.lastname: Ménard
mesh_terms: D006801:Humans; D006973:Hypertension / Q000097:blood / Q000175:diagnosis; D007118:Immunoassay / Q000379:methods*; D012083:Renin / Q000097:blood*
chemical_list: D012083:Renin