Ma. Brown et al., PRIMARY HYPERALDOSTERONISM - A MISSED DIAGNOSIS IN ESSENTIAL HYPERTENSIVES, Australian and New Zealand Journal of Medicine, 26(4), 1996, pp. 533-538
Background: It has been recognised recently that primary hyperaldoster
onism may be more common than previously thought, the frequency of dia
gnosis being improved by screening using a plasma aldosterone concentr
ation to renin activity ratio. Aims: To determine the frequency of pri
mary hyperaldosteronism, screening with both plasma aldosterone to ren
in concentration (PRC) and activity (PRA) ratios, in normokalaemic sub
jects previously diagnosed as having essential hypertension. Methods:
Plasma potassium, aldosterone and PRCs and PRA and blood pressure (BP)
were measured in 74 hypertensive subjects previously diagnosed by one
physician as having essential hypertension. A normal range for plasma
aldosterone/renin ratios was determined in 147 control subjects. Hype
rtensive subjects with elevated aldosterone/renin ratios were further
assessed for primary hyperaldosteronism using saline loading and fludr
ocortisone suppression. Those in whom plasma aldosterone concentration
exceeded 140 pmol/L after suppression tests underwent adrenal vein sa
mpling for measurement of aldosterone and cortisol concentrations as w
ell as adrenal CT scanning to diagnose the cause of primary hyperaldos
teronism. The main outcome measures were a diagnosis of aldosterone pr
oducing adenoma or bilateral adrenal hyperplasia based upon adrenal ve
in sampling. Results: Four subjects (5%) had an elevated plasma aldost
erone to renin ratio using PRC and six (8%) using PRA. Two subjects (2
.7%) in this selected population had primary hyperaldosteronism, both
of whom had BP > 160/110 mmHg at the time of testing. Conclusions: The
frequency of normokalaemic primary hyperaldosteronism appears to be g
reater than previously thought, though the true incidence in the gener
al population of hypertensive subjects remains unknown. The sensitivit
y of diagnosis (but not specificity) may be improved by measurement of
the plasma aldosterone/renin ratio and PRC is at least as adequate as
PRA for this process.