USEFULNESS OF SHORTENED SALINE INFUSION TEST FOR PRIMARY ALDOSTERONISM DIAGNOSTICS

Abstract

Objective: Primary aldosteronism (PA) is a frequent and remediable cause of endocrine hypertension. Saline infusion test (SIT) is one of the most widely-accepted confirmatory tests for PA, but some patients may not tolerate the standard loading volume of 2 L saline over 4 h. Shortened SIT, loading only 1 L saline over 2 h, has been suggested to be useful and would be more acceptable across wider population if the diagnostic utility proves to be comparable to the standard SIT. Therefore, we compared the diagnostic values of plasma aldosterone concentration after 2 hours of 1 L saline loading (2 h PAC) and those after 4 hours of 2 L saline loading (4 h PAC) for the prediction of unilateral aldosterone hypersecretion and postoperative outcome. Design and method: The retrospective, single-center study involved 555 PA-suspected patients who underwent recumbent SIT, 153 of whom subsequently underwent adrenal vein sampling (AVS). Postoperative blood pressure outcome was also examined in 37 patients. We calculated the defined daily doses (DDD) of anti-hypertensive drugs according to those set by the World Health Organization, and compared the values between before and 1 year after the surgery. Results: The Youden Index of 2 h PAC for receiver operating characteristic (ROC) curves of 4 h PAC > 60 pg/mL (The SIT was considered positive if 4 h PAC was over 60 pg/mL according to the Japan Endocrine Society 2009 guidelines) was 66 pg/mL. The areas under the ROC curves of 2 h and 4 h PAC were comparable (0.80 vs.0.85, 95% CI -0.1035 – 0.0109, P = 0.11) for unilateral aldosterone hypersecretion defined as lateralization index >4. Postoperative reduction of anti-hypertensive drug use and 2 h PAC was significantly correlated (P = 0.04). The areas under the ROC curves of 2 h and 4 h PAC were comparable (0.82 vs.0.78, 95% CI -0.0949 – 0.1706, P = 0.58) for postoperative reduction of anti-hypertensive drug use. Conclusions: Shortened SIT may be similarly useful as standard SIT to select PA patients for AVS and also to predict postoperative blood pressure outcome with reduced burden on patients.