Background: The upright serum aldosterone/upright plasma renin activity ratio( ARR) has been recommended as a screening tool for the diagnosis of primary aldos teronism. Objective: We reviewed the data collected from hypertensive patients i n order to define retrospectively the cut-off values and evaluate the reliabili ty of the ARR and of the saline infusion test in the diagnosis of primary aldost eronism. Patients: In 157 patients referred to our unit with a suspicion of prim ary aldosteronism, 61 of whom had confirmed primary aldosteronism[26 aldosterone -producing adenoma(APA); 35 idiopathic hyperaldosteronism], the supine and upri ght ARR, and the ARR after the administration of captopril and losartan were cal culated, and the results of the saline infusion test were analysed. Results: Cho osing 40 as the cut-off value, the upright ARR had 100%sensitivity and 84.4%s pecificity. The post-captopril and post-losartan ARR were slightly more specif ic, but at the cost of a lower sensitivity. A cut-off value of 7 ng/dl for seru m aldosterone at the end of the saline infusion in patients with an upright ARR of 40, gave 100%specificity and a positive predictive value. Furthermore, APA p atients showed increased mean levels of aldosterone/ cortisol ratio after the sa line infusion test. Conclusion: Our data reinforce the superiority of a standard ized upright ARR as a screening test in the diagnosis of primary aldosteronism, identifying 40 as an ideal cut-off value. Saline infusion represents a useful t est to confirm such a diagnosis, with a serum aldosterone level of 7 ng/dl as a satisfactory cut-off value. Some more information is obtained when the aldoster one/cortisol ratio is considered.
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