Quantitative determination of homocysteine from dried blood spot, serum, or plasma. Performed by high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS).
This method enables accurate quantification of total homocysteine, a key biomarker for cardiovascular risk assessment, B-vitamin status evaluation, and methylation pathway function.
Clinical indications include:
| Analyte / Group | Components | Clinical Significance |
|---|---|---|
| Homocysteine | Total homocysteine (tHcy) | Sulfur-containing amino acid; elevated levels (hyperhomocysteinaemia) are an independent risk factor for cardiovascular disease |
Total homocysteine includes free, protein-bound, and oxidised forms, all reduced during sample preparation to provide a single total concentration.
Homocysteine is a sulfur-containing amino acid formed during the metabolism of methionine. It sits at a critical metabolic junction where it can either be remethylated back to methionine (requiring folate and vitamin B12) or transsulfurated to cysteine (requiring vitamin B6). Disruption of either pathway leads to elevated homocysteine levels.
Generally considered the upper limit of normal
Key cofactors in homocysteine remethylation
Common genetic variant affecting homocysteine metabolism
Elevated homocysteine (hyperhomocysteinaemia) is an established independent risk factor for atherosclerotic cardiovascular disease, venous thromboembolism, and stroke. The relationship between homocysteine and vascular damage involves endothelial dysfunction, oxidative stress, and prothrombotic effects.
Homocysteine is also a sensitive functional marker of B-vitamin status. Elevated levels commonly indicate deficiency of folate, vitamin B12, or vitamin B6, even when serum levels of these vitamins appear normal. This makes homocysteine testing particularly valuable in populations at risk of B-vitamin deficiency, including the elderly, vegetarians, and patients with malabsorption.
The MTHFR C677T polymorphism is one of the most common genetic variants affecting homocysteine metabolism. Individuals homozygous for this variant (TT genotype) typically have 20–40% higher homocysteine levels and may require higher folate intake to maintain normal methylation function.
The test is performed using isotope-dilution high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Total homocysteine is measured following reduction of all disulfide bonds and protein precipitation, ensuring complete recovery of free, bound, and oxidised forms.
Available from DBS, serum, or plasma. DBS collection is particularly advantageous for remote sampling and population screening, while plasma/serum collection follows standard venepuncture protocols.
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