The influence of aging on the diagnosis of primary aldosteronism.

Primary aldosteronism (PA) is common in young or middle-aged hypertensive patients, but PA among the elderly has recently become more common. As salt sensitivity increases with age, plasma renin activity (PRA) tends to decrease, whereas the aldosterone-to-renin ratio (ARR) tends to increase in the elderly. The aim of this study was to clarify the influence of aging on the diagnosis of PA. We retrospectively evaluated 155 consecutively admitted patients who were not taking antihypertensive medications or calcium channel blockers and α blockers that underwent PRA and plasma aldosterone concentration (PAC) measurements. The study subjects included 13 PA and 69 essential hypertensive (EHT) patients aged over 65 years, and 32 PA and 41 EHT patients under aged 65 years. Our study clarified the influence of aging through screening and confirmatory tests for the diagnosis of PA. Our results showed the ARR cutoff value for a screening test to be 556 (area under the curve: AUC=0.906), its sensitivity and specificity to be 84.6% and 89.9%, respectively, and the likelihood ratio to be 8.34 in the elderly, whereas the ARR cutoff value was 272 in the non-elderly. In the saline infusion test, the mean PAC was 86.6 ± 41.8 pg ml(-1) in the elderly and 158.1 ± 116.5 pg ml(-1) in the non-elderly (P = 0.04). There was no influence from age in both the captopril challenge test and the furosemide upright test. Aging may influence PA screening and saline infusion tests; thus, we should consider the influence of aging in the diagnosis of elderly subjects with PA.