11C-metomidate PET CT versus Adrenal Vein Sampling for diagnosing surgically curable primary aldosteronism: prospective test validation, and impact of somatic genotype and ethnicity on outcomes

Primary aldosteronism (PA) due to a unilateral aldosterone-producing adenoma (APA) is a common, curable cause of hypertension, but invasive methods of diagnosis and treatment contribute to <1% of patients being offered the chance of cure. The primary objective of our prospective within-patient study in 143 patients with PA was to compare accuracy of 11C-metomidate (MTO) PET-CT scanning with adrenal vein sampling (AVS) in predicting biochemical cure from PA and resolution of hypertension. Secondary outcomes addressed heterogeneity of underlying pathogenesis and prediction of patients most likely to achieve complete cure of hypertension. 128 patients reached 6-9 month follow-up. 77/78 surgical patients achieved one or more of the four hierarchically analysed Primary Aldosteronism Surgical Outcome (PASO) criteria for biochemical and clinical success. MTO was not superior to AVS but all four differences in accuracy favored MTO, with 95% CIs >-17%, the pre-specified margin of non-inferiority. The best univariate predictors of complete clinical cure were home systolic blood pressure (SBP) <135 mmHg after one month of spironolactone 100 mg daily (odds ratio 13.0 (3.72, 45.24) p<0.001) and KCNJ5 genotype of the APA (odds ratio 10.37 (2.50, 42.99) p=0.001). The latter remained significant in logistic regression on age, gender, ethnicity, and was itself predicted by elevated urine 18-hydroxycortisol:cortisol ratio. Our findings validate 11C-metomidate PET-CT for accurate, non-invasive detection of patients with unilateral PA, and identify patients most likely to benefit from adrenalectomy.