Short-term saline infusion test for subtype classification in primary aldosteronism

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 723-757-Renin-Angiotensin-Aldosterone System/Endocrine Hypertension
Bench to Bedside
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-731
Mika Tsuiki*1, Kazutaka Nanba1, Aya Tsumagari1, Kanako Nakao1, Rieko Nakatani1, Maiko Kakita1, Youhei Ueda1, Takeshi Usui1, Tetsuya Tagami1, Akira Shimatsu1, Akiyo Tanabe2 and Mitsuhide Naruse1
1National Hospital Organization Kyoto Medical Center, Kyoto, Japan, 2Tokyo Women's Med Univ, Tokyo, Japan
Objectives: Saline infusion test (SIT) is one of the most representative confirmatory tests for the diagnosis of primary aldosteronism (PA) and has been demonstrated to be useful in the subtype testing as well. It should however be indicated with caution in patients with uncontrolled hypertension or congestive heart failure.

Aims of the study were to investigate 1) the diagnostic criteria for subtype classification and 2) whether SIT is reliable when carried out with a shorter infusion period.

Subjects and methods: Forty three patients with PA were studied. Twenty eight were diagnosed as bilateral PA (Bil-PA) and 15 were diagnosed as unilateral PA (Unil-PA) by CT, adrenal venous sampling and histopathological analysis after surgery. SIT was performed by infusing 2 liters of saline over 4 hrs. Blood samples for PAC were obtained at 2hrs (PAC2h) and 4hrs (PAC4h). Distinguishing Unil-PA from Bil-PA criteria of SIT were assessed using ROC curve analysis.

Results: PAC2h and PAC4h in patients with Unil-PA were significantly higher than those with Bil-PA (289±114 vs. 88±44 pg/ml; 301±132 vs. 72±31pg/m) (p<0.01). Using the ROC curve analysis, the optimal cutoff value of PAC2hr for distinguishing Unil-PA from Bil-PA was 120pg/ml (sensitivity 100%, specificity 85.7%) and that of PAC4h was 135pg/ml (sensitivity 93.3%, specificity 96.4%). AUC of both of them were not significantly different (0.971 for PAC2h vs. 0.974 for PAC4h).

Conclusions: The SIT is useful for subtype classification of PA. In addition, the test can be shortened to 1litter infusion of saline over 2hrs with 120pg/ml as the best cutoff limit. The present study therefore suggest that short-term SIT could be used as confirmatory and subtype testing.

Nothing to Disclose: MT, KN, AT, KN, RN, MK, YU, TU, TT, AS, AT, MN

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