Endocrine Abstracts

Introduction: The posture test (PT), developed to distinguish idiopathic adrenal hyperplasia (IAH) from aldosterone producing adenoma (APA), has been postulated as inaccurate. In 2007, standardized diagnostic methods, including PT for subclassification, were introduced in Landspitali University Hospital (LUH), housing the only endocrine department in Iceland. The aim of this study is to review the results of PT performed in LUH in 2007–2016.

Methods: Charts for all patients ≥18 years old, diagnosed with primary aldosteronism (PA) during 2007–2016 in LUH, were retrospectively reviewed. After screening, verification of PA was made with saline infusion test. During PT, s-aldosterone, s-renin and s-potassium were measured after a 10-h bed-rest and again after subsequent 4-h upright-position. If s-aldosterone increased by >50%, the test was considered positive. Thereafter, patients underwent a CT-scan and adrenal venous sampling (AVS). Adrenalectomy was offered if PA was found unilateral by AVS.

Results: Out of 49 PA-patients undergoing PT during the period, 22 had unilateral disease and 27 bilateral. The unilateral group (UG) consisted of 14 patients with APA and 4 with IAH. Three are awaiting surgery and one histopathological examination was inconclusive. Average increase of s-aldosterone during PT in the bilateral group (BG) was 217±127%, significantly higher than 88±26% in the UG (P=0.008). A greater proportion of the BG had a positive PT, 81% (22/27) versus 55% (12/22) of the UG, P=0.04. Positive predictive value of the PT with regards to bilateral disease was 0.65 (22/34), sensitivity 0.81 (22/27) and specificity 0.45 (10/22).

Conclusions: In this nationwide study we found the PT to have fairly high sensitivity but low specificity in subclassifying PA, supporting previous reports of inaccuracy. Although the PT is not conclusive, it could be informative in addition to CT-scan for treatment decision if a patient is unable to undergo AVS for practical reasons.