Specimen Collection Manual and Test Catalog

0.5 mL serum; minimum 0.25 mL.

Do not collect in serum separator tube.

Collect specimen in a non-additive red top tube. Spin down immediately and pour off into a 13 x 75 mm plastic transport tube.

Frozen.

Room temperature: 7 days. Refrigerated: 7 days. Frozen: 28 days.

Gross hemolysis • Moderate hemolysis • Grossly lipemic • Grossly icteric • Serum separator tube

This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the U.S. Food and Drug Administration. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

Quest test code 94621, 18-Hydroxyco, 18-OH Corticosterone

Primary aldosteronism should be suspected whenever a patient has the triad of hypertension, hypokalemia, and inappropriate renal potassium wasting. The biggest challenge is the differential diagnosis between the more common adrenal adenoma and bilateral hyperplasia. Because adrenal adenomas increase the circulating levels of 18-hydroxycorticosterone (18-OH B), serum levels of 18-OH B may be useful to differentiate them from bilateral adrenal hyperplasia. The cutoff point appears to be about 50 ng/dL of serum. Most values are around 100 ng/dL. The higher the level of this precursor, the greater the possibility that an adrenal adenoma is present. J Clin Endocrinol Metab. 97: 881-9, 2012.