Contralateral Suppression Index as a Surrogate Marker for Aldosterone Lateralization in Simulated Incomplete Adrenal...

To evaluate the contralateral suppression index (CSI) as a diagnostic tool for predicting aldosterone lateralization under simulated incomplete adrenal vein sampling (AVS) and to assess the impact of adrenal nodules and age on its performance.

This study retrospectively reviewed consecutive patients who underwent AVS for primary aldosteronism between January 1, 2016, and June 30, 2024. A total of 362 patients were analyzed. Bilaterally selective studies were reanalyzed by masking 1 adrenal side to simulate incomplete sampling. CSI was calculated from the available adrenal vein and inferior vena cava samples and tested across 3 thresholds (≥1.0, ≥0.5, and ≥0.2) using lateralization index (LI) ≥4.0 as the reference. Performance metrics included positive predictive value (PPV), sensitivity, and specificity, overall and stratified by adrenal nodules and age (<35 vs ≥35 years).

Mean CSI was 0.33 in lateralized cases (LI ≥ 4.0) and 3.16 in nonlateralized cases (P < .001). Without a concordant nodule, CSI ≤1 supported lateralization (PPV, 70%; sensitivity, 88%; specificity, 94%); stricter thresholds increased certainty, with CSI ≤0.5 yielding a PPV of 98% and specificity of 99% (sensitivity, 61%) and CSI ≤0.2 achieving a PPV and specificity of 100% (sensitivity, 28%). With a concordant nodule, PPVs were 94%, 99%, and 100% at CSIs ≤1, ≤0.5, and ≤0.2, respectively, with sensitivity of 98%-64% . Results were consistent across age groups.

CSI reliably predicted aldosterone lateralization under simulated incomplete AVS. Thresholds of ≤0.5 and ≤0.2 provided confirmatory accuracy, particularly when combined with concordant imaging.