Aldosterone Levels Post-IV Saline Suppression Using Commercial Reference Laboratory Liquid Chromatography-Tandem Mass...

Diagnostic cutoffs for primary aldosteronism (PA) post-intravenous (IV) saline suppression have not been well established. These cutoffs are based on old immunoassays and, more recently, on liquid chromatography tandem mass spectrometry (LC-MS/MS) assays performed in research settings. Aldosterone levels associated with PA post-IV saline suppression using commercially available reference laboratory LC-MS/MS assays are unknown. Our objective was to report our experience measuring aldosterone levels postsaline infusion using a commercial reference laboratory LC-MS/MS assay.

A retrospective chart review was conducted. A total of 35 patients who underwent a saline suppression test with aldosterone levels measured using a commercial reference laboratory LC-MS/MS assay were included. Patients were classified into 2 groups: no PA (n = 9) and confirmed PA (n = 26) based on postsurgical outcomes (histopathology and PA surgical outcome criteria) and, for those on medical treatment, clinical and biochemical response to therapy. Aldosterone levels at baseline and after 2 L of IV normal saline infusion over 4 hours were analyzed and compared between the groups.

Median baseline aldosterone levels were higher in patients with confirmed PA, 16.0 ng/dl (IQR: 14.0, 26.0) versus 11.0 ng/dl (IQR: 6.0, 13.0), P = 0.016. The median aldosterone levels postsaline infusion in the confirmed PA group were 11.5 ng/dl (IQR: 8.0, 18.0) compared to 1.0 ng/dl (IQR: 1.0, 2.0) in the no PA group. In the latter, none of the patients had an aldosterone level >3.0 ng/dl.

Using an LC-MS/MS aldosterone assay from a commercial reference laboratory, we report that saline suppression in patients with confirmed PA can detect aldosterone levels as low as 4.0 ng/dl. These results need to be confirmed with larger studies.