Cysteine, total

cys

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.
Method(s): GC-MS/MS (1), LC-MS/MS (2).

Indication(s)

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

Frozen, on dry ice. (for general instruction on transportation, click here)

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.

Literature

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.

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