9B.07

Abstract

Objective: The aldosterone to renin ratio(ARR)is currently the most reliable available means of screening for Primary aldosteronism. It could be measured in the supine, seating or upright positions. The Endocrine Society and recent French guidelines recommended screening primary aldosteronism by the measurement of ARR in the seating position. The aim of this work is to study the influence of postural changes on ARR in patients with suspected secondary hypertension & to evaluate sensitivity and specificity of seated ARR compared to supine and upright ARR.Design and method: 43 patients were prospectively hospitalized for secondary hypertension exploration (age 51 ± 16,5; SBP/DBP:139 ± 12/85 ± 9mmHg, number of antihypertensive drugs:2 ± 1). After a conventional washout of drugs interfering with renin angiotensin aldosterone system, plasma aldosterone concentration was measured by RIA method(Normal values: 40–175ng/l)and direct renin concentration(DRC)with CLIA method (Normal values: 4,2–59.7 μUI/l). Aldosterone and renin samples were collected in the morning, at bed after an overnight supine position, then out of bed after 1 hour of upright position and finally 2 hours later after 15 minutes in seating position. When DRC was <5 μUI/l it was counted 5 μUI/l as recommended. Results: Referring to ARR cut-off value of 23pg/μUI, the sensitivity of seated ARR was 50% with a specificity of 96.5%. The negative predictive value was 80% and the positive predictive value was 87.5%. Compared to these results, a cut-off value of 19pg/μUI improved sensitivity to 85.7% with a specificity of 89.6%. Negative predictive value and positive predictive value were 92.8%and80% respectively. Seated ARR mean value(17 ± 15pg/μUI/l) was lower than supine and upright ARR, respectively measured at 23 ± 20pg/μUI and 24 ± 20pg/μUI. This could be explained by an overall increase in DRC at seating compared to the supine position with a mean increase by factor 2.2 (53 μUI/l vs 24 μUI/l), whereas at the same time, aldosterone just slightly increased by a factor 1.05(235ng/l vs 223ng/l). Seated ARR correlated to supine and upright ARR with correlation coefficients (r)of 0.89 and 0.93 respectively (p < 0,0001). Conclusions: Current recommended measurement of ARR in the seating position is fairly correlated to ARR in supine and upright positions. However, even if the recommended cut-off value of 23pg/μUI offers a good specificity, a suggested cut-off value of 19pg/μUI increases the discriminating power of this test.