Preferred Sample Type
Suitable Specimen Types
- EDTA Plasma
Sample Processing in Laboratory
Immediately
Sample Preparation
Plasma must be spun down and frozen within 1 hour of venesection
Turnaround Time
2-3 weeksSample Stability
Plasma is stored on receipt at -20°C until analysis. It is acceptable to receive unfrozen samples from other laboratories in the post and then freeze samples on arrival.
Homocysteine/ Homocystine (HCYS)
General Information
Homocysteine (HCYS) has been linked to the occurrence of atherosclerosis and may cause deep venous thrombosis, coronary and peripheral vascular disease, stroke (CVA) and neural tube defects in pregnancy. HCYS levels increase with age and can be reduced by vitamin B supplements - particularly folic acid.
Homocysteine is a non-protein amino acid with the formula HSCH2CH2CH(NH2)CO2H.
Homocysteine is not obtained from the diet. Instead, it is biosynthesized from methionine via a multi-step process. First, methionine receives an adenosine group from ATP, a reaction catalyzed by S-adenosyl-methionine synthetase, to give S-adenosyl methionine (SAM). SAM then transfers the methyl group to an acceptor molecule, (i.e., norepinephrine as an acceptor during epinephrine synthesis, DNA methyltransferase as an intermediate acceptor in the process of DNA methylation). The adenosine is then hydrolyzed to yield L-homocysteine. L-Homocysteine has two primary fates: conversion via tetrahydrofolate (THF) back into L-methionine or conversion to L-cysteine.
Patient Preparation
Must be fasted overnight
Reference Range
Deficiencies of the vitamins folic acid (B9), pyridoxine (B6), or B12 (cobalamin) can lead to high homocysteine levels. Supplementation with pyridoxine, folic acid, B12 or trimethylglycine (betaine) reduces the concentration of homocysteine in the bloodstream.
Elevations of homocysteine also occur in the rare hereditary disease homocystinuria and in the methylene-tetrahydrofolate-reductase polymorphism genetic traits. The latter is quite common (about 10% of the world population) and it is linked to an increased incidence of thrombosis and cardiovascular disease.
Sample analysed by tandem mass spectrometry. Please note new reference range as of March 2013.
6.7 - 15.2 µmol/L
Specifications
- EQA Scheme?: Yes
- EQA Status: UK NEQAS