FRI150 Individualized And Shorter Follow-up With Immunohistochemical Staining In Unilateral Primary Aldosteronism?

Disclosure: H. Gunnarsdottir: None. B.A. Agnarsson: None. S. Jonasdottir: None. J. Gudmundsson: None. G. Birgisson: None. H.Á. Sigurjónsdóttir: None. Indroduction: Clinical significance of specific antibody staining (SAS) for unilateral primary aldosteronism (PA) has been unclear. Individualized follow-up of PA patients could be in sight. Long-term outcome of patients, classified based on immunohistochemical staining, needs further investigation. Aims: We aimed to assess long-term clinical outcome (using PASO criteria) for unilateral PA, classifying patients based on SAS. Methods: The study was a nationwide observational study, with up to 11 years follow-up, executed in 2007-2016 at Landspitali National University Hospital of Iceland, tertiary referral center. Patients were diagnosed and treated in line with the current guidelines. All unilateral PA patients, ( n=26) age 28-73 years, who underwent adrenalectomy in Iceland during the study period were included. H&E stained tissue slides were stained using specific CYP11B1 and -B2 antibodies. All cases were re-evaluated and classified as adenoma (APA) or non-adenoma (adrenal hyperplasia, unilateral adrenal micronodules (UMN) or aldosterone producing cell clusters (APCC)). Data collection consisted of aldosterone, renin and cortisol values, antihypertensive drug count, potassium supplementation, blood pressure and serum potassium pre-intervention and throughout follow-up and histopathology results post-adrenalectomy. Results: Following SAS, APA was seen in 21 adrenals, APCC in three and UMN in two. Immunohistochemical staining altered histopathological diagnosis in 27% of the patients. Around 80% of each subgroup had partial clinical success. No APA patient with complete clinical success at 12 months (n=4) relapsed during follow-up. Conclusions: We found SAS mandatory for accurate histopathological diagnosis of PA. Our results indicate that a subgroup of APA patients can be discharged safely early. Presentation: Friday, June 16, 2023