title: Diagnosis of primary aldosteronism: value of different screening parameters and influence of antihypertensive medication.
abstract: OBJECTIVE
  The aim of this study was to investigate the utility of different screening techniques for primary aldosteronism (PA), including serum aldosterone (SA), plasma renin activity (PRA) and the SA/PRA ratio in hypertensive patients of a tertiary-care centre. Furthermore, the influence of antihypertensive medication on SA and the SA/PRA ratio were studied.
  
  
  METHODS
  Clinical records of 425 hypertensive patients who had SA and PRA measurements over a 27-month period were analysed retrospectively. Eighty patients were excluded from further analysis because of incomplete data. The remaining 345 patients were classified into the following groups: patients with essential hypertension (EH) (n=260, 75.4%), patients with PA (n=49, 14.2%) and patients with secondary hypertension other than PA (n=36, 10.4%). Diagnosis of PA was made in accordance with established laboratory criteria (including measurements of SA, PRA, urinary excretion of aldosterone and metabolites, imaging techniques and response to treatment).
  
  
  RESULTS
  Although mean serum potassium values were significantly lower (P<0.001) in the PA group compared with the EH group, 61% of PA subjects were normokalaemic (3.4-5.2 mmol/l). The SA/PRA ratio alone identified 94% of the patients with PA, but was false positive in 30% of the patients with EH. The SA/PRA ratio together with SA>150 g/ml increased the diagnostic accuracy, led to the correct identification of 84% of the patients with PA, and decreased the false-positive rate to 3%. A multivariate binary logistic regression analysis based on SA and PRA was performed, which identified PA with 90% sensitivity and 91% accuracy. The SA(2)/PRA or the SA(3)/PRA ratio was found useful for simplification of the regression analysis. Antihypertensive medication influenced SA, PRA and the SA/PRA ratio only in EH patients. In EH patients taking beta-adrenoceptor antagonists PRA tended to be lower, leading to a significantly higher SA/PRA ratio and therefore increasing the false-negative rate.
  
  
  CONCLUSIONS
  To reduce false-positive results in screening for PA, and thereby avoid unnecessary and cost-intensive diagnostic procedures, SA should be taken into account in addition to the SA/PRA ratio as a second screening criterion. Alternatively, the SA(2)/PRA or the SA(3)/PRA ratio is more accurate screening tests than the SA/PRA ratio. Beta-blockers should be avoided whilst screening for PA.
authors.affiliation: Division of Endocrinology, Medical Department II, Klinikum of the Albert-Ludwigs-University Freiburg, Germany. seiler@medizin.ukl.uni-freiburg.de
authors.forename: Lysann
authors.initials: L
authors.lastname: Seiler
authors.forename: Lars C
authors.initials: LC
authors.lastname: Rump
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schulte-Mönting
authors.forename: Marc
authors.initials: M
authors.lastname: Slawik
authors.forename: Katrin
authors.initials: K
authors.lastname: Borm
authors.forename: Hermann
authors.initials: H
authors.lastname: Pavenstädt
authors.forename: Felix
authors.initials: F
authors.lastname: Beuschlein
authors.forename: Martin
authors.initials: M
authors.lastname: Reincke
mesh_terms: D000450:Aldosterone / Q000097:blood* / Q000652:urine; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D005260:Female; D006801:Humans; D006929:Hyperaldosteronism / Q000097:blood* / Q000150:complications / Q000175:diagnosis; D006973:Hypertension / Q000097:blood* / Q000188:drug therapy / Q000209:etiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011188:Potassium / Q000097:blood; D011237:Predictive Value of Tests; D012083:Renin / Q000097:blood*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D000959:Antihypertensive Agents; D000450:Aldosterone; D012083:Renin; D011188:Potassium