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Methylmalonic Acid and Homocysteine
Test Code91003
CPT Codes
83090, 83921
Preferred Specimen
2.7 mL serum
Minimum Volume
1.1 mL
Other Acceptable Specimens
Serum collected in: Trace metal-free (royal blue-top) tube • Plasma collected in: Sodium heparin (green-top) or sodium heparin trace element free (royal blue-top) tube
Instructions
Red top tubes: Place the specimen in a refrigerator or ice bath for 30 minutes after collection. Centrifuge the specimen as soon as possible after complete clot formation has taken place. Transfer the serum to a plastic screw-capped vial.
Barrier gel separator tubes: Place the specimen in a refrigerator for 30 minutes after collection. Centrifuge the specimen as soon as possible after complete clot formation has taken place. Do not place barrier tubes in an ice bath as freezing may prevent the barrier gel from adequately separating serum from cells.
EDTA or heparin tubes: Place the specimen in a refrigerator or ice bath until the specimen can be centrifuged. Centrifuge the specimen as soon as possible and transfer the plasma to a plastic screw-capped vial.
Barrier gel separator tubes: Place the specimen in a refrigerator for 30 minutes after collection. Centrifuge the specimen as soon as possible after complete clot formation has taken place. Do not place barrier tubes in an ice bath as freezing may prevent the barrier gel from adequately separating serum from cells.
EDTA or heparin tubes: Place the specimen in a refrigerator or ice bath until the specimen can be centrifuged. Centrifuge the specimen as soon as possible and transfer the plasma to a plastic screw-capped vial.
Transport Temperature
Refigerated (cold packs)
Specimen Stability
Room temperature: 4 days
Refrigerated: 7 days
Frozen: 6 months
Refrigerated: 7 days
Frozen: 6 months
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Whole blood • Unseparated serum or plasma
Methodology
Methylmalonic Acid: Mass Spectrometry (MS) • Homocysteine: Enzymatic
Setup Schedule
See indiviual assays
Clinical Significance
An elevated concentration of Homocysteine is an independent risk factor for cardiovascular disease. When used in conjunction with Methylmalonic Acid (MMA), these tests are useful to diagnose and monitor Vitamin B12 (cobalamin) and folic acid deficiency and are often useful in evaluating macrocytosis (an elevated MCV, an erythrocytic index).
