Is single oral administration of captopril beneficial in screening for primary aldosteronism?

Plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were measured in 19 cases with primary aldosteronism (PA) and in 72 with essential hypertension (EHT) to differentiate the two disorders during the following conditions on normal salt diet: after overnight recumbency (basal state) and 2 hours after oral administration of 25 mg of captopril. Screening criteria were determined so that all PA patients were diagnosed as positive, and their specificities were compared with those of other conventional screening methods for PA. After captopril administration, the specificity of a criterion based on a combination of PAC and PAC/PRA ratio was 93% and positive predictive value was 79%. This criterion was superior to blood pressure response to angiotension II analog infusion, PRA on salt depletion, and to PAC on salt loading. However, higher specificity (97%) and positive predictive value (90%) were obtained from a criterion based on a combination of basal PAC and PAC/PRA ratio. Therefore, the use of a combination criterion based on PAC and PAC/PRA ratio at basal state rather than after captopril administration may give a satisfactory result in the screening for PA.