Post saline infusion test aldosterone levels indicate severity and outcome in primary aldosteronism

Introduction: The most widely used confirmatory test for primary aldosteronism (PA) in Germany is the saline infusion test (SIT). The SIT results are judged as follows: post-test aldosterone levels < 50 ng/l exclude whereas levels > 50 ng/l confirm PA. We hypothesize that the height of post SIT aldosterone levels indicates the severity of PA.

Patients and methods: 256 prospective PA patients of German Conn Registry underwent SIT, and were re-evaluated every 6 to 12 months thereafter. The data of 126 of 256 patients with complete follow up 1.15 ± 0.29 years after diagnosis were analyzed. Assessment included complete PA testing, metabolic and hormonal parameters, blood pressure, renal function, as well as documentation of comorbidities. Patients were divided into two groups with post-SIT aldosterone 50 – 100 ng/l (n = 38) and > 100 ng/l (n = 88).

Results: Patients with post-SIT aldosterone > 100 ng/l had significant shorter duration of hypertension (11.3 ± 11.4 vs. 16.4 ± 12.5 years, p = 0.014), higher systolic blood pressure (151 ± 16 vs. 143 ± 17 mmHg, p = 0.036), lower serum potassium (3.28 ± 0.56 vs. 3.53 ± 0.39 mmol/l, p = 0.006), higher 24h urine protein excretion (38 ± 91 vs. 18.7 ± 63 mg/dl, p = 0.012), and were more often female (p = 0.038). They showed more often unilateral disease (p < 0.005) with larger tumors (14 ± 10 vs. 7 ± 10 mm, p = 0.021), underwent more often adrenalectomy (75% vs. 36.8%, p < 0.005), had lower number of antihypertensive drugs at follow-up (1.2 ± 1.2 vs. 2.5 ± 1.4, p = 0.001) and faster normalization of urinary albumin excretion (p = 0.033) at follow-up. No differences were seen in frequency of comorbidities.

Conclusions: PA patients with post-SIT aldosterone > 100 ng/l seem to have a more rapid and progressive form of PA caused more frequently by unilateral disease with larger APAs.