Reassessment of postural stimulation testing as a simple tool to identify a subgroup of patients with unilateral primary aldosteronism.

Context Adrenal vein sampling (AVS) represents the current diagnostic gold standard for differentiation between unilateral and bilateral primary aldosteronism (PA). Postural stimulation testing (PST) has been used to provide additional diagnostic information. Objective To evaluate diagnostic utility of PST in the differential diagnosis of PA. Design Cohort study. Setting Single tertiary reference center. Patients We analyzed 106 PST performed between 2008 and 2020. Diagnosis of PA and cause of PA were determined according to the Endocrine Society Clinical Practice Guideline, taking into account results of saline infusion testing, AVS, preoperative imaging and outcome after medical or surgical treatment. Main outcome measures The suggested cut-offs for the diagnosis of unilateral PA were revisited and optimized for high specificity using receiver operating characteristics (ROC)-analysis. Results 106 patients had confirmed PA (unilateral PA: n=55, bilateral PA: n=29, AVS unsuccessful/declined by patients: n=22). Based on decreased aldosterone plasma concentration of ≥ 28% after 4 hours in the upright position, the PST showed a sensitivity of 36.4% at a specificity of 100% to identify unilateral disease (AUC=0.72, 95% CI=0.62-0.83, p=0.001). In patients with valid testing (drop of cortisol ≥ 10% after 4 hours, n=53) sensitivity of PST rose to 51.4% at a specificity of 100% (AUC=0.77, 95% CI=0.65-0.90, p=0.001). Conclusion The high specificity of 100% for the detection of unilateral PA in patients with decreased aldosterone by at least 28% after 4 hours, makes PST a simple, non-invasive contribution to subtype differentiation in PA.