48 hours after setup at PeaceHealth Laboratories’ reference lab.
CPT Code:
83921-90
Specimen Collection Details
Collection:
One 7.5 mL serum separator tube (SST). Also acceptable: One 4 mL lavender top tube (EDTA), 4 mL green top tube (sodium heparin), 4.5 light blue top tube (sodium citrate), or 4 mL grey top tube (sodium fluoride/potassium oxalate).
Handling:
Allow to clot, centrifuge and separate serum or plasma from cells into a plastic vial. Freeze. Keep cold if there is more than one freeze/thaw cycle. If multiple tests are ordered, send separate specimen for this test.
Stability:
18 hours ambient, 4 days refrigerated, or 1 month frozen. NOTE: Ambient stability cited from Hitchcox, K. et al. Stability of Biochemical Analytes in Blood Specimens Subjected to Delayed Processing. The FASEB Journal 2008 22:1102,3.
Standard Volume:
3 mL serum or plasma.
Minimum Volume:
1.5 mL serum or plasma.
Transport:
Frozen on dry ice.
Comments:
Serum methylmalonic acid is elevated in most patients with cobalamin deficiency. Methylmalonic acid and homocysteine are substrates for the two cobalamin-dependent enzymes, methyl-malonyl-CoA mutase and N5-methyltetrahydro-folate: homocysteine transferase. Methylmalonate accumulates in man when a cobalamin deficiency state exists which is identified by low normal concentrations of vitamin B12. Quantitation of serum methylmalonate provides a functional test for adequacy of vitamin B12. In a patient with low normal vitamin B12 levels that are due to vitamin B12 deficiency, serum methylmalonate is usually >0.4 µmol/L in the fasting state.
Rejection Criteria:
Thawed or ambient specimen; gross hemolysis or lipemia.
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