Diagnostic Value of ACTH Stimulation Test in Determining the Subtypes of Primary Aldosteronism

Background: Adrenal venous sampling is recommended as the golden standard for subtyping primary aldosteronism (PA). However, it is invasive and inconvenient, and seeking a better way to make differential diagnosis of PA is necessary. Objective: The objective of the study was to evaluate the diagnostic value of ACTH stimulation test under 1 mg dexamethasone suppression test (DST) in determining the subtypes of PA. Methods: Ninety-five patients with PA confirmed by saline infusion test were included in this study. According to adrenal venous sampling and histopathology, 39 patients were diagnosed as bilateral adrenal hyperplasia (BAH), 37 as aldosterone-producing adenoma (APA), and 19 as unilateral adrenal hyperplasia (UAH). An ACTH stimulation test under 1mgDST was performed in all patients. Plasma aldosterone and cortisol levels were measured every 30 minutes until 120 minutes after the iv injection of 50 IU ACTH. Results: During the ACTH stimulation test, aldosterone levels in APA and UAH were similar (P > .05) but higher than those in BAH (P < .001). Furthermore, stimulated aldosterone levels of unilateral PA (APA and UAH) were significantly higher than bilateral PA (BAH) (P < .001). Receiver-operated characteristics curve analyses showed the aldosterone after ACTH stimulation was effective for distinguishing between unilateral PA and bilateral PA. The diagnostic accuracy was highest at 120 minutes after ACTH stimulation, and the optimal cutoff value of the aldosterone was 77.90 ng/dL, with a sensitivity of 76.8%, a specificity of 87.2%, a positive predictive value of 89.6%, and a negative predictive value of 72.3%. Conclusions: The ACTH stimulation test under 1mg DST is useful to determine the subtypes of PA, especially in unilateral and bilateral PA, and may guide further treatment in PA patients.