Pheochromocytoma and paragangliomas (PPGLs) are catecholamine producing neoplasms, originating from the chromaffin cells of the adrenal medulla or from extra-adrenal sympathetic ganglia, respectively. 1 PPGL prevalence in the hypertensive population is estimated between 0.2% and 0.6%. 2 If left untreated, PPGLs are associated with an increased risk for cardiovascular morbidity and mortality; thus, early diagnosis and treatment are imperative. 3,4
Objective:
Saline infusion test (SIT) for confirmation of primary aldosteronism (PA) traditionally requires two liters of normal saline and is 240 minutes long. Previous studies have raised concerns regarding increased blood pressure (BP) and worsening hypokalemia during and after SIT. Therefore, we aim to evaluate the diagnostic applicability of a shorter, one liter 120-minute-long SIT.
Design and method:
A cross-sectional study, including all consecutive patients with suspected PA who underwent SIT from 1st January 2015 to 31st December 2022 in a large, tertiary medical center in Israel. Blood samples were drawn for renin and aldosterone at baseline (t = 0), after 2 hours (t = 120 min), and after 4 hours (t = 240 min) of saline infusion. Receiver-operator curve (ROC) analysis was used to evaluate the sensitivity and specificity of various aldosterone cutoff values at t = 120 for the confirmation of PA. Logistic regression was performed to analyze the association of baseline variables and aldosterone levels after 120 minutes and after 240 minutes.
Results:
The final analysis included 55 patients. ROC analysis with an area under the curve (AUC) of 0.97 (95% CI [0.93, 1.00], P < 0.001) demonstrated 90% specificity and 92% sensitivity for an aldosterone cutoff value of 342 pmol/L at t = 120 to confirm PA. 45% (25/55) of patients did not suppress aldosterone levels after 240 minutes, of them 92% (23/25) did not suppress aldosterone at t = 120 according to the 342 pmol/L cutoff. Univariate analysis showed that male sex, hypokalemia, and elevated systolic BP were all associated with failure to suppress aldosterone levels below the traditional threshold for PA confirmation at t = 240 (i.e. <276 pmol/L), as well as below 342 pmol/L at t = 120. Mean systolic BP (SBP) at t = 0 was 139.9±21.2 mm/Hg and increased to 146.2±14.1 mm/Hg (p = 0.016) during the SIT.
Conclusions:
We present data showing that an aldosterone cutoff of 342 pmol/l at t = 120 has both high sensitivity and specificity for PA diagnosis confirmation.
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