Endocrine Abstracts

Introduction: The estimation of urinary aldosterone is one of the recommended confirmatory tests when diagnosing primary aldosteronism (PA). The study assessed the interpretation of the urinary aldosterone secretion (UA).

Subjects and methods:: The study enrolled both healthy volunteers and patients with suspected PA. Estimation of UA in 24-hour urine specimen was performed in enrolled individuals. Increased oral salt intake was recommended before and during urine collection. The data of healthy volunteers were intended to facilitate the interpretation of the data of patients with suspected PA. In patients with suspected PA, saline infusion testing (SIT) was performed twice in order to definitely confirm or exclude PA diagnosis. Both SITs were performed under identical conditions, i.e. after the drugs interfering with renin-angiotensin-aldosterone system were withdrawn. The individuals who exhibited discordant SIT results were excluded from the study.

Results: Based on the data of 30 healthy volunteers, upper UA reference value was determined: 43 nmol/day when urinary sodium exceeded 200 mmol/day.

Eighty-five urine samples from 45 patients with suspected PA were used to analyze the UA interpretation. In respect to PA diagnosis based on SIT, UA >19 nmol/day was characterized by 96% sensitivity and UA > 92 nmol/day was associated with 96% specificity. Upper reference value based on the data from healthy volunteers was characterized by 77% sensitivity and 60% specificity.

Conclusions: Urinary aldosterone can reliably confirm or exclude the diagnosis of primary aldosteronism. However, this approach is applicable only in a limited number of individuals who exhibit very low or very high urinary aldosterone secretion.