Total choline esters (as opposed to free choline), after liberation of choline from phospholipids (mainly phosphatidylcholine) in the presence of phospholipase D (PLD) and calcium.
The concentrations of the other metabolites in serum/plasma obtained from platform C are not affected by PLD treatment, and are simultaneously measured by this modified assay.
Method(s): LC-MS/MS (1).
Assessment of one-carbon status. Choline deficiency.
Patient/subject: Prandial status affects the concentration, which increases after a meal. The subjects should be fasting.
Matrix: Serum or plasma. Total choline concentration (as opposed to the concentration of free choline) is not affected by the preanalytical conversion of phospholipids to free choline in serum.
Volume: Minimum volume is 50 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: Stable in frozen stored serum/plasma for years.
Reported values: 2-3 mmol/L.
Intraclass correlation coefficient (ICC): na.
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