Method(s): GC-MS/MS (1), LC-MS/MS (2).
What is measured: Total homocysteine (tHcy), which includes homocysteine-cysteine mixed disulphide (Hcy-Cys), free homocysteine (fHcy) and bound homocysteine (bHcy), after quantitative reductive cleavage of all disulphide bonds.
Platform C: Chol, (tChol), TMAO, Bet, DMG, tHcy, Creat, Crn, Met, MetSo, Cysta, tCys, His, 3-MH, 1-MH, Arg, ADMA, SDMA, hArg, TML
Performance of the assay (GC-MS/MS)
Lower limit of detection (LOD): 0.1 µmol/L.
Within-day CV: 1 %; between-day CV: 2 %.
Assessment of folate and cobalamin status; risk factor for cardiovascular disease. Total homocysteine is the preferred metabolic marker of cobalamin status in infants (3).
Specimen, collection and processing
Patient/subject: Prandial status affects concentration, which increases slightly after a protein rich meal..
Matrix: Serum or plasma.
Volume: Minimum volume is 50 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: Homocysteine is released from the blood cells, and the resulting artificial increase is inhibited at low temperature. The plasma/serum fraction must be separated from the blood cells, preferentially within 30-60 minutes. After such separation, total homocysteine is stable.
Transportation; for general instruction on transportation, click here.
Frozen, on dry ice.
Reported values, interpretation
Reported values: <15 µmol/L. The upper reference limit is lower in in infants (< 6.5 µmol/L) and in pregnant women. Concentration increases in renal failure.
Intraclass correlation coefficient (ICC): 0.72.
1. Midttun, Ø., McCann, A., Aarseth, O., Krokeide, M., Kvalheim, G., Meyer, K., and Ueland, P.M. (2016). Combined measurement of 6 fat-soluble vitamins and 26 water-soluble functional vitamin markers and amino acids in 50 μL of serum or plasma by high-throughput mass spectrometry. Anal Chem 88, 10427-436.
2. Midttun, O., Kvalheim, G., and Ueland, P.M. (2013). High-throughput, low-volume, multianalyte quantification of plasma metabolites related to one-carbon metabolism using HPLC-MS/MS. Anal Bioanal Chem 405, 2009-017.
3. Bjorke-Monsen, A.L., Torsvik, I., Saetran, H., Markestad, T., and Ueland, P.M. (2008). Common metabolic profile in infants indicating impaired cobalamin status responds to cobalamin supplementation. Pediatrics 122, 83-91.