When you have elevated homocysteine levels
A blood sample is obtained by inserting a needle into a vein in the arm.
No test preparation is needed
The methylenetetrahydrofolate reductase (MTHFR) gene oversees the production of the MTHFR enzyme. This enzyme changes one form of folate into another and is part of the process that converts homocysteine into methionine, an important building block for many proteins.
MTHFR testing detects two relatively common DNA sequence variants (single nucleotide polymorphisms, SNPs) in the MTHFR gene, C677T and A1298C. These SNPs result in changes in the DNA (or mutations) and are associated with increased homocysteine levels in the blood. Approximately 10% of the British population is homozygous for C677T. The prevalence is higher in those of Mediterranean and lower in those of African or Indian Asian descent. The rise in homocysteine within the bloodstream is worsened when the affected person is folate-deficient or if they have inherited multiple mutations.
How is it used?
The methylenetetrahydrofolate reductase (MTHFR) mutation test is used to detect two relatively common mutations in the MTHFR gene that are associated with elevated levels of homocysteine in the blood. It is not routinely performed within the UK.
An MTHFR test is not recommended, nor homocysteine, in diagnostic testing for inherited high clotting risk, thrombophilia. There is also no role for testing is cardiovascular risk assessment either.
Though the MTHFR test may be used to help determine the cause of elevated homocysteine, the value of measuring homocysteine levels outside of people presenting with homocystinuria is not clear. Homocystinuria is detected by the neonatal heel prick screen therefore most people born in the UK will have had homocystinuria excluded at birth.
When is it requested?
What does the test result mean?
If a person has two copies (homozygous) of MTHFR C677T, or has one copy of C677T and one of A1298C, then it is likely that elevated homocysteine levels in that person are due to these inherited mutations, or that the mutations are contributing to them. Other, rarer MTHFR genetic mutations will not be detected with typical testing.
Is there anything else I should know?
MTHFR mutations are a rare cause of homocystinuria, a condition caused by a defective enzyme that disrupts methionine metabolism, leads to greatly increased amounts of homocysteine in the blood and urine, and causes a variety of complications. The most common cause of this condition is a deficiency in the cystathionine B-synthase (CBS) enzyme. The MTHFR mutations that cause homocystinuria are typically not detected by this test.
Who performs MTHFR testing?
Can my MTHFR genes change?
If I have the same MTHFR gene mutations as a relative, why is my homocysteine level significantly different?
On This Site
Tests: Homocysteine, Factor V Leiden Mutation and PT 20210 Mutation,Vitamin B12 & Folate, Cardiac Risk Assessment, Methotrexate
Conditions: Heart Disease, Cardiovascular Disease, Hypercoagulable Disorders, Neural Tube Defects, Stroke
Elsewhere On The Web
Genetics Home Reference: MTHFR
NIH, Genetic and Rare Diseases Information Center: Homocysteinemia due to MTHFR deficiency
BIMDG : British Inherited Metabolic Disease Group TEMPLE Guides; Homocystinuria
GOV UK: Homocystinuria (HCU): detailed information
A British Society for Haematology guideline:Thrombophilia testing