The cutoff value of aldosterone-to-renin ratio for the diagnosis of primary aldosteronism in patients taking antihypertensive medicine

Background. Primary aldosteronism (PA) may account for as much as 6-20% of cases of refractory hypertension referred to hypertension clinics. Because antihypertensive agents affect the physiologic renin-angiotensin-aldosterone system, screening diagnostic tests for PA are generally performed after antihypertensive agents are discontinued. However, such tests can be dangerous for patients with severe hypertension or other cardiovascular complications. However, a reliable cutoff value for the aldosterone-to-renin ratio (ARR) has not been established, especially for Asians, including the Japanese. Method. Fifty-five consecutive patients with clinically suspected PA were evaluated from July 10, 2001, to March 1, 2005, at the National Cardiovascular Center in Japan. Every referred patient was screened prospectively for PA with the ARR at the outpatient clinic. The patients tested continued to be treated with a variety of antihypertensive agents. We reviewed the sensitivity, specificity, and accuracy of the ARR without modifying the antihypertensive agents. The diagnosis of PA was established with the results of both abdominal computed tomography and adrenal scintigraphy. Results. Of the 55 patients, 27 were found to have PA, including adrenal adenoma (n = 18) and bilateral adrenal hyperplasia (n = 9). The mean ARR of patients with PA was significantly higher than that of patients without PA. By assuming a cutoff value of the ARR >= 69 calculated from the receiver operating characteristics curve, the highest sensitivity (81%), specificity (82%), positive-predictive value (81%), and negative-predictive value (81%) were obtained. Conclusion. The data suggest that an ARR >= 69 strongly indicates PA in Japanese patients with hypertension being treated with antihypertensive agents.