title: Active renin versus plasma renin activity to define aldosterone-to-renin ratio for primary aldosteronism.
abstract: BACKGROUND
  In recent years, the assessment of the plasma aldosterone-to-renin ratio (ARR) has become an established screening method for the diagnosis of primary aldosteronism. Plasma renin activity (PRA) is usually measured to define ARR although, increasingly, renin concentration alone is often measured in clinical routine.
  
  
  OBJECTIVE
  To determine the threshold of ARR using active renin concentration to screen for primary aldosteronism.
  
  
  METHODS
  To determine the ARR threshold based on plasma immunoreactive renin concentration (irR), we measured plasma aldosterone concentration (PAC), irR and PRA in 36 hypertensive patients, nine thereof with adrenal adenoma, and compared ARRs calculated from irR and PRA, respectively.
  
  
  METHODS
  Single-centre, hypertension clinic in a tertiary care hospital.
  
  
  RESULTS
  PRA ranged from 0.41-14.9 ng/ml per h and irR from 1.1-72 ng/l. There was an excellent correlation between PRA and irR (r = 0.98, P < 0.0001) and between ARRPRA and ARRirR (r = 0.96, P < 0.0001). An ARRPRA > 750 pmol/l per ng/ml per h was previously found to be highly predictive of primary aldosteronism because 90% of the corresponding patients failed to suppress PAC upon saline infusion or fludrocortisone. The corresponding threshold value for ARRirR was 150 pmol/ng in our patients. Using these cut-offs, nine subjects had both increased ARRPRA and ARRirR while, in three patients, either ARRPRA or ARRirR were increased. The nine patients with increased ARRPRA and ARRirR also had PAC > 650 pmol/l. Only these patients had adrenal adenomas.
  
  
  CONCLUSIONS
  The ARR threshold to screen for primary aldosteronism may be based on measurement of irR. An ARRirR > 150 pmol/ng may indicate primary aldosteronism.
authors.affiliation: Department of Nephrology, Fremantle Hospital, University of Western Australia, Fremantle, Australia. paolo.ferrari@health.wa.gov.au
authors.forename: Paolo
authors.initials: P
authors.lastname: Ferrari
authors.forename: Sidney G
authors.initials: SG
authors.lastname: Shaw
authors.forename: Jérôme
authors.initials: J
authors.lastname: Nicod
authors.forename: Esther
authors.initials: E
authors.lastname: Saner
authors.forename: Jürg
authors.initials: J
authors.lastname: Nussberger
mesh_terms: D000236:Adenoma / Q000097:blood / Q000378:metabolism; D000310:Adrenal Gland Neoplasms / Q000097:blood / Q000378:metabolism; D000328:Adult; D000368:Aged; D000450:Aldosterone / Q000096:biosynthesis / Q000097:blood*; D004056:Differential Threshold; D005260:Female; D006801:Humans; D006929:Hyperaldosteronism / Q000097:blood* / Q000175:diagnosis*; D006973:Hypertension / Q000097:blood; D015592:Immunoradiometric Assay; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D012083:Renin / Q000097:blood*
chemical_list: D000450:Aldosterone; D012083:Renin