Vitamin E (α-Tocopherol).

What does this test assess?

This method quantifies α-tocopherol (the most biologically active form of vitamin E) from a dried blood spot. Vitamin E is the body's principal lipid-soluble antioxidant, and its measurement is critical in evaluating oxidative stress status and diagnosing deficiency-related neuromuscular disease.

Clinical indications include:

• Diagnosis and monitoring of vitamin E deficiency, particularly in fat malabsorption disorders
• Assessment of neurological symptoms including ataxia, peripheral neuropathy, and myopathy
• Monitoring in cholestatic liver disease and abetalipoproteinaemia (Bassen-Kornzweig syndrome)
• Evaluation in cystic fibrosis and short bowel syndrome where fat-soluble vitamin absorption is impaired
• Premature infant monitoring — neonates are born with low tocopherol stores and are vulnerable to haemolytic anaemia
• Supplementation efficacy monitoring in clinical and research settings

About Vitamin E

Vitamin E encompasses a group of eight naturally occurring compounds — four tocopherols and four tocotrienols — of which α-tocopherol is the most abundant and biologically active form in human tissues. It is preferentially retained in the body via hepatic α-tocopherol transfer protein (α-TTP).

α-Tocopherol functions primarily as a chain-breaking antioxidant, intercepting lipid peroxyl radicals within polyunsaturated fatty acid-rich cell membranes. This protective role is particularly important in tissues with high metabolic rates and oxygen exposure, including the brain, retina, and skeletal muscle.

Deficiency is rare in the general population but clinically significant in patients with fat malabsorption, genetic defects in α-TTP (causing ataxia with vitamin E deficiency, AVED), or cholestatic liver disease. Progressive spinocerebellar ataxia, peripheral neuropathy, and retinitis pigmentosa are hallmark features of prolonged deficiency. In premature neonates, low vitamin E stores contribute to haemolytic anaemia and retinopathy of prematurity.

Vitamin E status is best interpreted in the context of circulating lipid levels, as tocopherol is transported in lipoproteins. The α-tocopherol:total lipid ratio may provide a more accurate assessment than absolute tocopherol concentration alone, particularly in patients with dyslipidaemia.

Analytical technique

α-Tocopherol is extracted from a dried blood spot and quantified by isotope-dilution LC-MS/MS using a deuterium-labelled internal standard (d6-α-tocopherol). The method provides high specificity, distinguishing α-tocopherol from γ-tocopherol and other tocopherol isoforms without chromatographic co-elution.

LC-MS/MS overcomes the limitations of older HPLC-UV and fluorescence methods, which are susceptible to interference from structurally similar compounds including γ-tocopherol and oxidation products.

Literature

1. Traber MG. “Vitamin E inadequacy in humans: causes and consequences.” Advances in Nutrition, 2014, 5(5):503–514. 10.3945/an.114.006254
2. Brigelius-Flohé R, Traber MG. “Vitamin E: function and metabolism.” FASEB Journal, 1999, 13(10):1145–1155. 10.1096/fasebj.13.10.1145
3. Ouahchi K et al. “Ataxia with isolated vitamin E deficiency is caused by mutations in the α-tocopherol transfer protein.” Nature Genetics, 1995, 9(2):141–145. 10.1038/ng0295-141
4. Niki E, Traber MG. “A history of vitamin E.” Annals of Nutrition and Metabolism, 2012, 61(3):207–212. 10.1159/000343106
5. Zhong G et al. “Determination of retinol and α-tocopherol in dried blood spots by LC-MS/MS.” Journal of Chromatography B, 2020, 1159:122363. 10.1016/j.jchromb.2020.122363