Primary aldosteronism (PA) is the most common cause of endocrine hypertension, with a prevalence rate of 6-12% in hypertensive patients. Aldosterone/renin ratio (ARR) is the screening test of choice for PA. Because of the variable cut-off points of ARR, reference values related to the populations and methods considered are recommended. (i)To optimize the ARR cut-off points for PA screening with current methods; (ii)to assess the correlation and diagnostic sensitivity of the plasma aldosterone concentration/plasma renin activity (ARR) ratio and the aldosterone concentration/renin concentration (ARC) ratios for PA screening, and (iii)to determine the prevalence of PA in our population. Plasma aldosterone concentration and plasma renin activity levels were measured using radioimmunoassays (RIAZENco Zentech and RIA DiaSorin respectively), while a chemiluminescence assay (Liaison Diasorin) was used to test renin concentration. ARR and ARC ratios were calculated in 345 subjects (136 healthy subjects and 209 hypertensive patients). Prevalence of PA was 5.9% after diagnostic confirmation. ROC curve analysis suggested an ARR threshold of 48.9(ng/dL)/(ng/mL/h) (100% sensitivity, 93.6% specificity) and an ARC threshold of 2.3(ng/dL)/(μIU/mL) (100% sensitivity, 90.9% specificity). Good correlation was seen between ARR and ARC (ρ=.83, P<.0001), with a presumptive diagnostic concordance of 96.6%. New cut-off values of ARR and ARC for screening of PA, with high sensitivity and good diagnostic concordance, were determined in the study population. It is important to have valid normal ranges to avoid diagnostic errors. Copyright © 2019 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.