P053 Angiotensin Ii Receptor Type 1 (At1) Autoantibodies in Patients With Primary Aldosteronism

Background: Primary aldosteronism (PA) is a common cause of hypertension and is characterized by excessive aldosterone secretion. Determination of PA subtype (i.e., unilateral vs. bilateral) is clinically important to inform treatment. Immune mechanisms may have a role in the pathogenesis of PA. The aim of this study was to examine whether angiotensin receptor type 1 (AT1) autoantibodies predict the underlying subtype of PA. Methods: We conducted a cross-sectional study of patients with PA who were referred for adrenal vein sampling (AVS). Patients had AT1 autoantibody titres measured. AT1 antibodies were defined as present when >17 U/mL, negative if <10 U/mL, and indeterminate if between 10-17 U/mL. AVS was used as a standard to determine PA subtype. The frequency of AT1 autoantibodies was determined according to PA subtype and major clinical predictors of lateralization. Results: 54 patients with successful AVS were included (mean age, 52.7 years; 46.3% male). Positive AT1 antibodies were detected in 14 (25.9%), negative antibodies in 32 (59.3%), and indeterminate antibodies in 8 (14.8%) patients. There was no significant association detected between AT1 antibody status and lateralization (p=0.39). There were no associations found between AT1 autoantibody status and any of the major clinical factors traditionally predictive of PA severity or prognosis, including sex (p=0.94), age (p=0.76), hypokalemia (p=0.91), estimated glomerular filtration rate (p=0.46), or aldosterone-to-renin ratio (p=0.58). Conclusion: AT1 autoantibodies are common in patients with PA; over a quarter of patients who underwent AVS in our study. However, AT1 autoantibodies were not predictive of PA subtype.