PS-BPC08-1: VALIDATION OF PRIMARY ALDOSTERONISM DIAGNOSIS DURING THE TRANSITIONAL PERIOD OF ALDOSTERONE ASSAY AND GUIDELINE CHANGES IN JAPAN

Abstract

Objectives and Methods: In Japan, the plasma aldosterone concentration (PAC) measurement method was changed from RIA to CLEIA method in April 2021. From then until August 2021, when the 2021 clinical practice guidelines for the diagnosis and management of primary aldosteronism (PA) were published, we diagnosed PA using the RIA-converted PAC value (conversion formula from CLEIA (X) to RIA (Y): Y = 1.174X + 42.3) and the conventional positive decision criteria of the screening and confirmatory tests in PA diagnosis. The new criteria were then used to re-determine and confirm the agreement. Results: PAC(CLEIA) and renin activity (PRA) or active renin concentration (ARC) were measured simultaneously for PA screening at our hospital from April to August 2021 in 122 patients (135 measurements in total). PAC values (CLEIA) were less than 4 pg/mL in 21 measurements (16%). This value was converted to PAC(RIA) at 47 pg/mL based on the formula. (i) PA screening tests: 10% of the measurements were found to be ‘not excluded’ by the conventional criteria and negative by the new criteria. This was due to the fact that the calculated PAC(RIA) values were higher than they should be when the conversion formula to RIA was applied to cases with low PAC(CLEIA) values, resulting in higher estimated ARR values (PAC(RIA)/PRA or PAC(RIA)/ARC ratio). (ii) PA confirmatory tests: In the captopril challenge test, one case was found to be positive by the conventional criteria and negative by the new criteria due to the same reason as that on point (i). In the saline infusion test, PAC(CLEIA) of 12–15 pg/mL was determined to be less than PAC(RIA) 60 pg/mL by the conversion formula, which was deemed negative by the conventional criteria but borderline by the new criteria. (iii) PA diagnosis using the confirmatory tests: In one case, the diagnosis did not match the positive (borderline) classification based on the new criteria, although the patient was deemed negative by the conventional criteria. This was due to discrepancies of the saline infusion test results. Conclusion: During the transition period of PA diagnosis from the RIA to CLEIA method, it was necessary to review the data and retest the patients according to their symptoms because of possible inconsistencies between the new and conventional criteria-based diagnostic results. PA diagnosis and treatment should be judged comprehensively on a case-by-case basis, without relying entirely on the values of the criteria.