5-Hydroxyindoleacetic acid (5-HIAA) is measured by C18 solid phase extraction (SPE) of an aliquot from a 24-hour urine collection and liquid chromatography/tandem mass spectrometry analysis using an amide-C16 high performance liquid chromatography column at a flow rate of 1.0 mL/min. 5-HIAA elutes apart from the bulk of the specimen matrix at a retention time of approximately 1.5 minutes. 5-HIAA is quantitated using a custom synthesized stable isotope labeled internal standard (d6-5-HIAA) from calibration over a concentration range 0.5 to 150 mg/L.(Kroll CA, Magera MJ, Helgeson JK, et al: A liquid chromatography-tandem mass spectrometry method for the determination of 5-hydroxyindole-3-acetic acid in urine. Clin Chem 2002;48:2049-2051)
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2 days (not reported on Saturday or Sunday)