title: Clinical validation for the aldosterone-to-renin ratio and aldosterone suppression testing using simultaneous fully automated chemiluminescence immunoassays.
abstract: BACKGROUND
  As larger numbers of hypertensive patients are screened for primary aldosteronism with the aldosterone-to-renin ratio (ARR), automated analyzers present a practical solution for many laboratories. We report the method-specific ARR cutoff determined with direct, automated chemiluminescence immunoassays allowing the simultaneous measurement of plasma aldosterone concentrations (PACs) and plasma renin concentrations (PRCs).
  
  
  METHODS
  Method comparisons to commonly employed assays and tandem mass spectrometry were undertaken. Patients were previously diagnosed based on the local ARR cutoff of 1.2 (ng/dl)/(μIU/ml) in samples collected in upright seated position. Lack of aldosterone suppression in response to salt load to less than 5 ng/dl confirmed primary aldosteronism. For the new assays, the optimal ARR cutoff was established in 152 patients with essential hypertension, 93 with primary aldosteronism and 147 normotensive patients. Aldosterone suppression was assessed in 73 essential hypertensive and 46 primary aldosteronism patients.
  
  
  RESULTS
  PAC and PRC were significantly correlated to values determined with currently available methods (P < 0.001). In patients with primary aldosteronism, patients with essential hypertension and controls, mean (95% confidence interval) PAC was 28.4 (25.4-31.8), 6.4 (5.9-6.9) and 6.2 (5.6-6.9) ng/dl, respectively. In the same groups, PRC was 6.6 (5.6-7.7), 12.9 (11.2-14.8) and 26.5 (22.2-31.5) μIU/ml. An ARR cutoff of 1.12 provided 98.9% sensitivity and 78.9% specificity. Employing the new assay aldosterone suppression confirmed the diagnosis of primary aldosteronism and essential hypertension using the cutoff of 5 ng/dl.
  
  
  CONCLUSIONS
  Our data demonstrate that the new assays present a convenient alternative for the measurement of PAC and PRC on a single automated analyzer. Availability of these simultaneous assays should facilitate screening and diagnosis of primary aldosteronism.
authors.affiliation: aImmunodiagnostic Systems Ltd, Boldon, Tyne and Wear, United Kingdom bMedizinische Klinik und Poliklinik IV, Klinikum der Ludwig Maximilians Universitaet, Munich cEndokrinologikum Berlin, Friedrichstr, Berlin, Germany dDepartment of Pathology and Laboratory Medicine, The University of British Columbia, Vancouver, British Columbia, Canada eCentro di Fisiologia Clinica e Ipertensione, Università di Milano, Ospedale Policlinico,Via Francesco Sforza, Milano, Italy.
authors.forename: Jenny
authors.initials: J
authors.lastname: Manolopoulou
authors.forename: Evelyn
authors.initials: E
authors.lastname: Fischer
authors.forename: Anna
authors.initials: A
authors.lastname: Dietz
authors.forename: Sven
authors.initials: S
authors.lastname: Diederich
authors.forename: Daniel
authors.initials: D
authors.lastname: Holmes
authors.forename: Riia
authors.initials: R
authors.lastname: Junnila
authors.forename: Philipp
authors.initials: P
authors.lastname: Grimminger
authors.forename: Martin
authors.initials: M
authors.lastname: Reincke
authors.forename: Alberto
authors.initials: A
authors.lastname: Morganti
authors.forename: Martin
authors.initials: M
authors.lastname: Bidlingmaier
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000450:Aldosterone / Q000097:blood*; D001794:Blood Pressure; D000075222:Essential Hypertension; D005260:Female; D006801:Humans; D006929:Hyperaldosteronism / Q000097:blood / Q000175:diagnosis*; D006973:Hypertension / Q000097:blood; D007118:Immunoassay / Q000379:methods; D049449:Luminescence; D008163:Luminescent Measurements / Q000379:methods; D008297:Male; D008875:Middle Aged; D012083:Renin / Q000097:blood*; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry
chemical_list: D000450:Aldosterone; D012083:Renin