Background: The saline suppression test (SST) serves to confirm the diagnosis of primary aldosteronism (PA) while adrenal vein sampling (AVS) is used to determine whether the aldosterone hypersecretion is unilateral or bilateral. An accurate prediction of bilateral PA based on SST results could reduce the need for AVS.
Aim: We sought to identify SST parameters that reliably predict bilateral PA.
Methods: The results from 121 patients undergoing SSTs at Monash Health from January 2010 to January 2018 including screening blood tests, imaging, AVS and histopathology results were evaluated. Patients were subtyped into unilateral or bilateral PA based on AVS and surgical outcomes.
Results: Of 113 patients with confirmed PA, 33 had unilateral disease while 42 had bilateral disease. In those with bilateral disease, plasma aldosterone concentration (PAC) was significantly lower post-SST, together with a significant fall in the aldosterone-renin ratio (ARR). The combination of PAC <300 pmol/L and a reduction in ARR post-SST provided 96.8% specificity in predicting bilateral disease. Eighteen out of 39 patients (49%) with bilateral PA could have avoided AVS using these criteria.
Conclusion: A combination of PAC <300 pmol/L and a fall in ARR post-saline infusion predicts bilateral PA with high specificity in patients undergoing the recumbent SST and may spare a significant number of patients from undergoing AVS. This will simplify the PA diagnostic process and reduce the demand for a costly and invasive procedure. This finding may be centre-specific, and therefore should be validated in an independent cohort.