Screening for primary aldosteronism with a logistic multivariate discriminant analysis

OBJECTIVE Primary aldosteronism (PA) is the most common endocrine cause of curable hypertension, but no single test unequivocally identifies it, Accor dingly, we investigated the usefulness of a logistic multivariate discrimin ant analysis (MDA) approach for PA screening, DESIGN Generation of a logistic MDA function based on retrospective analysi s of biochemical tests in a large cohort of referred patients with/without confirmed Conn's adenoma (CA), followed by prospective validation of the mo del, PATIENTS We investigated 574 selected hypertensives: 206 (32 with and 174 w ithout CA) retrospectively, 48 (with a 13% prevalence of CA) prospectively for the validation of the model, and 320 referred hypertensives (with a 3.4 % prevalence of CA) similarly evaluated, Patients were referred to a specia lised centre for hypertension (4th Clinica Medica-University of Padua) and to a department of Internal Medicine of a regional hospital (Reggio Emilia) , MEASUREMENTS In all patients we measured several demographic and biochemica l variables and performed a captopril test, A stepwise analysis of variance , based on a model fitted with several different variables, identified base line (sALDO) and captopril-suppressed plasma aldosterone (cALDO), supine pl asma renin activity (sPRA) and K+ as the most informative. Therefore, two m odels of logistic MDA with sPRA, K+, and either sALDO (model A) or cALDO (m odel B) were developed and used. ROC analysis was also performed to assess the optimal cut-off values. RESULTS The model B of MDA provided the best performance and identified CA with 100% sensitivity and 81% accuracy. When used prospectively it showed 1 00% sensitivity, both in the Padua (88% accuracy) and in the Reggio Emilia series (90% accuracy), However, at both institutions most patients with idi opathic hyperaldosteronism (IHA) were also detected. CONCLUSIONS Thus, although developed from patients with confirmed Conn's ad enoma, a strategy based on multivariate discriminant analysis can be used p rospectively for accurate screening for primary aldosteronism. Furthermore, it was proven to be accurate and applicable to patients tested with simila r modalities at a different institution, Although this approach did not pro vide a clear-cut discrimination of Conn's adenoma from idiopathic hyperaldo steronism, it may avoid unnecessary and costly further testing in patients with a low probability of primary aldosteronism.