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|Methodology:||High Performance Liquid Chromatography (HPLC)|
|Released:||1-4 days after setup at PeaceHealth Laboratories’ reference lab.|
|Specimen Collection Details|
|Collection:||NOTE: Collect after an overnight fast. One 4 mL green top tube (heparin). Also acceptable: One 5 mL red top tube. Protect from light during collection, storage, and transport.|
|Handling:||Allow to clot, centrifuge and immediately separate serum or plasma into a plastic vial. Protect from light during storage and transport. Freeze immediately. Critical frozen. Allow no more than one freeze/thaw cycle. If multiple tests are ordered, send separate specimen for this test.|
|Stability:||After separation from cells specimen stable 4 hours refrigerated or 2 months frozen. Unstable ambient.|
|Standard Volume:||1 mL serum or plasma.|
|Minimum Volume:||0.5 mL serum or plasma.|
|Transport:||Frozen on dry ice.|
|Comments:||EDTA is not acceptable as a specimen collected in EDTA yields a higher pyridoxal 5-phosphate concentration.
Vitamin B6 deficiency causes an increase in xanthurenic acid in individuals ingesting sufficient tryptophan.
|Rejection Criteria:||Specimen frozen and thawed more than once; specimen not frozen within 4 hours of collection; EDTA; whole blood.|
|Adult: 5.0-30.0 ng/mL|