COMPARISON OF PARTIAL SEATED SALINE INFUSION TEST AND SEATED SALINE INFUSION TEST FOR THE DIAGNOSIS OF PRIMARY ALDOSTERONISM

Abstract

Objective: Seated saline infusion test (SSIT) has proved to be much more sensitive to recumbent saline infusion test (RSIT) in confirmation of primary aldosteronism (PA), highly specific, much cheaper and less complicated than fludrocortisone suppression testing (FST). However, SSIT requires the subjects to keep sitting position for 4.5 h, which is not comfortable for all patients, especially for the elderly. The purpose of this study was to explore the diagnostic consistency between more free and comfortable partial seated saline infusion test (PSSIT) and SSIT. Design and method: The current study involved 89 hypertensive patients who had positive results in the screening test and underwent both PSSIT and SSST for the confirmation of PA. For SSIT, patients remained sitting posture for 4.5 hours (0.5 h before the basal measurement of PAC at 9am local time and during the whole process of saline infusion). For PSSIT, patients remained sitting posture for 0.5 h before the measurement of basal PAC and 0.5 h before the completion of saline infusion, for the rest of the time in the process of infusion, subjects were permitted to adopted more free and comfortable posture. Two liters of 0.9% NaCl was administered intravenously over 4 h during SSIT or PSSIT. The diagnostic consistency between PSSIT and SSIT was analyzed. Results: The plasma aldosterone concentration (PAC) after PSSIT was significantly lower than that of SSIT (6.06 vs 7.07ng/dL, P < 0.001). Eight patients (9%) who had post-PSSIT PAC less than 10ng/dl had post-SSIT PAC greater than 10ng/dl. The two saline infusion tests had lower correlation coefficient (r = 0.246, P = 0.02) and intra group correlation coefficient (ICC = 0.194, P = 0.015). ROC analysis predicted optimal cut-off aldosterone levels of 5.385 ng/dl for PSSIT with high sensitivity (80%) but low specificity (50%) when use 6 ng/dl for SSIT according to the Endocrine Society Guideline. Conclusions: The optimal cut-off values of PAC for PSSIT were lower than that of SSIT with high sensitivity but low specificity, which need to be noted in clinical application.