Endocrine Abstracts

Background: Primary aldosteronism (PA), the most common cause of secondary hypertension, often goes under-diagnosed due to limitations in current screening and confirmatory tests. With laboratories shifting to liquid chromatography–mass spectrometry (LC-MS) over immunoassays for measuring aldosterone, the improved accuracy has initiated a re-evaluation of diagnostic criteria, particularly regarding the saline infusion test (SIT). Despite the shift, LC-MS-specific cut-offs have not been sufficiently defined. This study aimed to establish and validate LC-MS-derived SIT thresholds to enhance diagnostic accuracy for PA.

Methods: This was a retrospective study, analysing patients investigated for PA between January 2019 and March 2025. Patients completed SIT, captopril challenge test (CCT), and/or adrenal vein sampling (AVS). Receiver operating characteristic (ROC) curve analysis was used to identify the optimal SIT cut-off, with PA diagnosis established by AVS and/or CCT.

Results: Of the 46 patients initially screened, 41 completed the SIT and were included in the analysis. PA was confirmed in 36 patients, while 5 were excluded based on negative confirmatory testing with CCT or AVS. Mean age was 49.6 ± 9.6 years, with 58.5% male and 41.5% female. Average BMI was 31.6 ± 7.7 kg/m². Relevant comorbidities included cardiac disease (7.3%), stroke (2.4%), diabetes (14.6%), and chronic kidney disease (CKD; 12.2%). Post-SIT aldosterone measured by LC-MS showed excellent diagnostic performance, with an area under the curve of 0.978. The optimal diagnostic threshold was 165 pmol/l (Youden Index), yielding 91.2% sensitivity and 100% sensitivity (PPV=100%; NPV=57%). Interestingly, all patients with CKD (n = 5) were diagnosed with PA.

Conclusion: A post-SIT plasma aldosterone threshold of 165 pmol/l, measured via LC-MS, demonstrated strong diagnostic performance for PA and has practical relevance for clinical application.