Seated Saline Suppression Test for Lateralizing Primary Aldosteronism

BACKGROUND: Confirmatory testing to identify lateralizing primary aldosteronism (PA) is of uncertain benefit. METHODS: Blinded clinical trial where patients with high-risk features for PA underwent the seated saline suppression test (SSST). All patients received adrenal vein sampling, where lateralization was defined by an aldosterone/cortisol ratio ≥3:1 comparing the dominant versus the nondominant sides. The primary outcome was the overall diagnostic accuracy of the SSST in identifying lateralizing PA using postinfusion aldosterone concentrations of ≥140 pmol/L (5.0 ng/dL) and ≥280 pmol/L (10.1 ng/dL) with immunoassay, and ≥162 pmol/L (5.8 ng/dL) with liquid chromatography/tandem mass spectrometry. RESULTS: A total of 160 patients completed the trial. Lateralizing PA was diagnosed in 98 patients (61.3%). The overall diagnostic accuracy of the SSST using an aldosterone cutoff of ≥140 pmol/L (5.0 ng/dL) and ≥280 pmol/L (10.1 ng/dL) was 64.4% (95% CI, 56.4-71.8) and 67.5% (95% CI, 59.7-74.7), respectively. A positive result was equivocal at the lower cutoff of ≥140 pmol/L (5.0 ng/dL; positive likelihood ratio, 1.1 [95% CI, 1.0-1.3]) and minimally informative at the higher cutoff of ≥280 pmol/L (10.1 ng/dL; positive likelihood ratio, 1.9 [95% CI, 1.3-2.7]). Negative results modestly ruled against lateralization using cutoffs of ≥140 pmol/L (5.0 ng/dL) and ≥280 pmol/L (10.1 ng/dL; negative likelihood ratio, 0.3 [95% CI, 0.1-0.9]; and 0.5 [95% CI, 0.3-0.7], respectively). The SSST properties were similar with liquid chromatography/tandem mass spectrometry. CONCLUSIONS: Aldosterone suppression testing is unreliable for anticipating adrenal vein sampling outcomes. The SSST may misinform diagnostic-treatment decisions. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04422756.