Vitamin A, serum
Clinical Background:
Vitamin A (retinol)
Vitamin A (Retinol) is a fat soluble vitamin present in meat and fish (especially liver). In addition many plant carotenoids such as beta-carotene can be converted to vitmain A ...
Vitamin A (retinol)
Vitamin A (Retinol) is a fat soluble vitamin present in meat and fish (especially liver). In addition many plant carotenoids such as beta-carotene can be converted to vitmain A by an oxygenase in the gut
After absorption in the small intestine vitamin A is transported via chylomicrons to the liver where it is either stored as retinyl estres or exported from the liver bound to retinol binding protein (RBP)
As retinal, vitamin A forms an important part of the visual pigment system. It exists combined with opsin to form rhodopsin . Light causes a change in retinal from the cis to the trans conformation which results in the generation of an electrical signal. As retinoic acid vitamin A interacts with nuclear receptors to modulate gene expression. Vitmain A plays a role in embryogenesis and in modulating the immune response.
Deficiency is usually due to dietary lack, malabsorption or liver disease and may lead to xerophthalmia and permanent eye damage. Blood measurements for vitamin A deficiency are limited as decreses are seen only with severe deficiency when hepatic reserves have fallen; additionally, infection depresses blood retinol, a negative acute phase response (check CRP), however, if Vitamin A <0.5umol/L, check for clinical deficiency.
Vitmain A tends to bioaccumulate so care is required in the dermatological use of retinoids due tot he possibility of teratogenicity, liver disease, musculoskeletal problems, reaised intracranial pressure, hypercalcaemia and renal insufficiency.
Test Details
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Discipline:
Biochemistry
Biochemistry
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Specimen Container Adult:
Serum (Gold/SST) or
Plasma (Purple/EDTA or Green/Lithium Heparin)
Serum (Gold/SST) or
Plasma (Purple/EDTA or Green/Lithium Heparin)
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Specimen Container Paediatric:
Serum (Gold/SST) or
Plasma (Purple/EDTA or Green/Lithium Heparin)
Serum (Gold/SST) or
Plasma (Purple/EDTA or Green/Lithium Heparin)
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Minimum Volume Adult:
1.0 mL
1.0 mL
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Minimum Volume Paediatric:
1.0 mL
1.0 mL
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Special Requirement:
Protect samples from light.
Protect samples from light.
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Sample Stability:
Stable for 6 hours unseparated.
Once separated freeze within 1 hour.Stable for 6 hours unseparated.
Once separated freeze within 1 hour. -
Transport Requirements:
Ambient temperature.
Ambient temperature.
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Add On Test:
No
No
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Quality Assurance:
NEQAS
NEQAS
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Reference Ranges:
Serum/plasma
<1 year 0 - 2.0 umol/L 1-11 years 1.0 - 2.0 umol/L 11-16 years 1.0 - 2.0 umol/L 16-19 years 1.0 - 3.0 umol/L Adult 1.05 - 2.8 umol/L Serum/plasma
<1 year 0 - 2.0 umol/L 1-11 years 1.0 - 2.0 umol/L 11-16 years 1.0 - 2.0 umol/L 16-19 years 1.0 - 3.0 umol/L Adult 1.05 - 2.8 umol/L -
Other Info:
Assay performed by HPLC with UV detection
Assay performed by HPLC with UV detection
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Routine Contact Name:
Duty Biochemist
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Routine Telephone:
Freeman: 0191 244 8889
RVI: 0191 282 9719
Freeman: 0191 244 8889
RVI: 0191 282 9719
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Routine Email:
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Specialist Test:
Yes
Yes