Significance of adrenocorticotropin stimulation test in the diagnosis of an aldosterone-producing adenoma.

CONTEXT

Adrenal venous sampling is the "gold standard" test in the diagnosis of an aldosterone-producing adenoma (APA) among patients with primary aldosteronism (PA) but is available only in specialized medical centers. Meanwhile, an APA is reported to be generally more sensitive to ACTH than idiopathic hyperaldosteronism.

OBJECTIVE

The aim was to evaluate the diagnostic accuracy of the ACTH stimulation test in the diagnosis of an APA among those with suspicion of PA.

PATIENTS AND SETTING

Fifty-nine patients admitted to Kyoto University Hospital on suspicion of PA were included in the study.

INTERVENTIONS

ACTH stimulation tests with 1-mg dexamethasone suppression were performed.

MAIN OUTCOME MEASURE

Plasma aldosterone concentrations (PAC) were examined every 30 min after ACTH stimulation. Receiver-operated characteristics curve analysis was used to evaluate the diagnostic accuracy.

RESULTS

PAC after ACTH stimulations were significantly higher in patients with an APA than in patients with idiopathic hyperaldosteronism or non-PA. Receiver-operated characteristics curve analyses showed that the PAC after ACTH stimulation was effective for the diagnosis of an APA among patients suspected of PA. The diagnostic accuracy was highest at 90 min after ACTH injection, with the optimal cutoff value greater than 37.9 ng/dl corresponding with sensitivity and specificity of 91.3 and 80.6% for the diagnosis of an APA.

CONCLUSIONS

Our study indicates that the ACTH stimulation test is useful in the diagnosis of an APA among patients suspected of PA. This test can be used to select patients who are highly suspected of an APA and definitely require adrenal venous sampling.