Quantitative methylmalonic acid analysis in plasma and urine is used to monitor the treatment of patients with methylmalonic acidemia due to either a defect in methylmalonyl-CoA mutase or cobalamin (B12) metabolism. Methylmalonic acid levels are also assessed as part of a comprehensive risk assessment for B12 deficiency in adults. Methylmalonic acid is measured by liquid chromatography and tandem mass spectrometry (LC-MS/MS) method.
- Plasma: 1-2 mL of blood in sodium heparin tube (green top) or EDTA tube (lavender top). A minimum of 0.5 mL blood (0.2 mL plasma) is required
- Urine: 5 mL (random or preferably morning first void) in a clean container without preservatives; freeze
- Ship overnight frozen on dry ice
- 3-5 days