FRI136 Adrenal Venous Sampling Criteria For Chemiluminescent Enzyme Immunoassay

Disclosure: K. Nakai: None. Y. Tsurutani: None. K. Irie: None. K. Teruyama: Employee; Self; Fujirebio Inc. J. Saito: None. M. Omura: None. T. Nishikawa: None. Objective: In primary aldosteronism (PA), plasma aldosterone concentration (PAC) was measured by radioimmunoassay (RIA), but the supply of the RIA kit was discontinued in March 2021 in Japan. The Japan Endocrine Society's 2021 Clinical Practice Guideline for the Diagnosis and Management of PA recommends that PAC measured by chemiluminescent enzyme immunoassay (CLEIA), which yields standardized LC-MS/MS compliant measurements, be used for clinical judgment. Because CLEIA shows a lower PAC than RIA, various cutoff values for PA need to be revised. Although conversion formulas for RIA and CLEIA for various kits have been provided, these conversions were studied mainly using samples representing aldosterone concentrations in peripheral blood; thus, it is unclear whether the same conversion formula can be used for samples obtained by adrenal venous sampling (AVS). In this study, we examined PAC conversion in AVS samples and the criteria for AVS when measured using CLEIA. Methods: PAC of 415 adrenal venous blood samples from AVS (including segmental AVS) from 63 patients with PA, were measured using RIA and CLEIA methods. The established conversion formula for PAC in peripheral blood samples was PAC (CLEIA) = 0.852 × PAC (RIA) − 36.0. PAC and aldosterone/cortisol ratio (A/C ratio) conversion formulas were determined between the two assays for AVS samples. Moreover, the CLEIA conversion value, which corresponds to the AVS criteria of conventional RIA, was obtained. Results: The median [interquartile range] PAC (CLEIA) in the samples was 9823.3 [3659.8-20600.5]. PAC measured using CLEIA was significantly correlated with RIA, and the correlation coefficient was 0.971. The PAC conversion formula determined was PAC (CLEIA) = PAC (RIA) × 0.7723 - 1199 pg/mL. PAC at 14,000 pg/mL in RIA was equivalent to 9,613 pg/mL in CLEIA. The correlation coefficient for the A/C ratio was 0.997, and the conversion formula was A/C (CLEIA) = A/C (RIA) × 0.7864 - 2.427. Discussion: Samples obtained from AVS had a much higher level of PAC than those obtained from peripheral blood. The PAC conversion formula for samples in AVS has a very large intercept compared with those in peripheral blood. Thus, the results of AVS tested by CLEIA should be interpreted with care because of the differences in the conversion formula. A different cut-off value may also be needed when evaluating the lateralization ratio because of the large intercept. Conclusion: PAC conversion formulas for AVS samples using CLEIA and RIA methods were obtained. The study outcomes are useful for interpreting AVS results using the CLEIA. Presentation: Friday, June 16, 2023