PS-BPR01-3: DISSOCIATION OF SERUM ALDOSTERONE CONCENTRATIONS BETWEEN THE MEASUREMENT METHODS: A CASE REPORT

Abstract

A 89-year-old woman was admitted to our hospital for syncope in 20XX-13. During the hospitalization, hypertension was pointed out. Despite 4 cm left adrenal mass suggestive of myelolipoma in contrast-enhanced magnetic resonance imaging (MRI), the serum and urine hormone levels in relation to secondary hypertension was within normal limits. Diagnosis of essential hypertension was made and treatment with olmesartan and azelnidipine was begun. In 20XX-5, her blood pressure was well controlled, and serum aldosterone level and active renin concentration (ARC) were 167 pg/ml and 6.8 pg/ml, respectively. Annual computed tomography (CT) scans showed virtually the same size of the adrenal tumor over 5 years. The trend toward increase in her blood pressure prompted us to repeat a blood test in 20XX, which turned out that serum aldosterone concentration was extremely high (1144 pg/ml), while ARC was suppressed to 1.7 pg/ml. In light of positive captopril challenge test, primary aldosteronism was suspected, and she was admitted to our hospital. However, systolic blood pressure was only mildly elevated (130 mmHg), though blood pressure medication had not been changed for 5 years. In addition, serum potassium value was 4.7 mEq/L and 24-hr urinary aldosterone was merely 3.4 μg/day under the salt-loaded state, which was inconsistent with exceedingly high serum aldosterone concentration and argued against the diagnosis of primary aldosteronism. Hence, validity of the method to quantitate serum aldosterone levels was questioned. To determine serum aldosterone concentration, radioimmunoassay (RIA) was applied in 20XX-5, yet chemiluminescent enzyme immunoassay (CLEIA) has been introduced since 20XX. Strikingly, reexamination of the same serum sample discovered that serum aldosterone value of 770 pg/ml in CLEIA was equivalent to 59 pg/ml by RIA method. As such, marked dissociation seems present between the two types of assays in this particular patient. Although tendency of correlation with regard to serum aldosterone levels between the two methods have been clarified, attention needs to be paid for the exception as in this case. Thus, it is fundamental to thoroughly evaluate patients with suspected primary aldosteronism as to whether the clinical course and serum aldosterone levels are compatible, and if not, it may be necessary to change the measurement method.