Diagnostic value of saline infusion test-derived biochemical parameters for primary aldosteronism subtyping.
Öztürk Yusuf Y, Karakurt Feridun F
Current clinical practice guidelines recommend adrenal venous sampling (AVS) for subtype classification in patients with primary aldosteronism (PA) who are candidates for adrenalectomy; however, AVS may be considered unnecessary in selected young patients with a high probability of unilateral disease. The additional diagnostic information provided by baseline and saline infusion test (SIT)-derived biochemical parameters when evaluated alongside clinical and radiological features remains uncertain. We aimed to compare the diagnostic performance of baseline and SIT-derived biochemical parameters for predicting unilateral PA and to evaluate the additional diagnostic information provided by each parameter when individually added to a common clinical-radiological framework. This retrospective study included 73 patients with PA (41 unilateral and 32 bilateral) who underwent successful AVS for subtype classification. Baseline plasma aldosterone concentration (PAC), baseline aldosterone-to-potassium ratio (APR), post-SIT PAC, SIT-derived APR, and the suppression index were evaluated. Diagnostic performance was assessed using receiver operating characteristic (ROC) curve analysis, while their associations within a common clinical-radiological model were evaluated using multivariable logistic regression analysis. Post-SIT PAC and SIT-derived APR showed the highest numerical discriminative performance among the evaluated biochemical parameters for predicting unilateral PA (AUC = 0.817 and 0.837, respectively). Adding either parameter individually to the common clinical-radiological model significantly improved model fit (likelihood-ratio p = 0.014 and p = 0.028, respectively); however, the increases in AUC were not statistically significant (ΔAUC = 0.022, p = 0.185 and ΔAUC = 0.017, p = 0.107, respectively). Post-SIT PAC and SIT-derived APR were strongly correlated (Spearman's ρ = 0.983, p < 0.001), and their ROC-derived thresholds yielded concordant classifications in 97.3% of patients. Our findings suggest that post-SIT PAC shows useful discriminative performance for predicting unilateral PA and may contribute to subtype assessment when considered alongside clinical and radiological features. These findings require validation in independent cohorts.