Method(s): LC-MS/MS (1).
What is measured: Free choline (as opposed to choline esters).
Performance of the assay
Lower limit of detection (LOD): 0.5 µmol/L.
Within-day CV: 5-8 %; between-day CV: 4-7 %.
Assessment of one-carbon status. Choline deficiency.
Specimen, collection and processing
Patient/subject: Prandial status affects the concentration, which increases 10-15 % after a meal. The subjects should be fasting.
Matrix: EDTA plasma. The concentration increases in a time- and temperature-dependent manner in serum, due to formation from choline esters, the concentrations of which are 100 fold higher. This conversion is inhibited by EDTA.
Volume: Minimum volume is 50 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: The blood sample must be immediately centrifuged and the plasma/serum fraction put on ice, and frozen. This is particularly important for serum samples.
Transportation; for general instruction on transportation, click here.
Frozen, on dry ice.
Reported values, interpretation
Reported values: 5-12 µmol/L.
Intraclass correlation coefficient (ICC) : 0.36.
1. 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.