Method(s): GC-MS/MS (1), LC-MS/MS (2).
What is measured: total cysteine (tCys), which includes cysteine mixed disulphide, free cysteine (fCys) and protein-bound homocysteine (bCys), 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, Cit, Orn, 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 homocysteine status.
Specimen, collection and processing
Patient/subject: Prandial status affects concentration, which increases slightly after a protein rich meal..
Matrix: Serum or EDTA plasma.
Volume: Minimum volume is 50 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: total cysteine is stable.
Transportation; for general instruction on transportation, click here.
Frozen, on dry ice.
Reported values, interpretation
Reported values: 150-350 µmol/L.
Reported value related to age and BMI.
Concentration increases in renal failure.
Intraclass correlation coefficient (ICC): 0.62.
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.