The Triene/Tetraene (T/T) ratio is another marker for essential fatty acid status. It is calculated as the ratio of Mead acid to arachidonic acid. This ratio, combined with measurements of the essential fatty acids and Mead acid, gives a more complete picture of the degree and nature of fatty acid deficiency. An elevated ratio shows a relative excess of triene (3 double bonds) compared to tetraene (4 double bonds), which results from essential fatty acid deficiency.
What is an "Essential fatty acid deficiency"?
Essential fatty acid (EFA) deficiency is rare, occurring most often in infants fed diets deficient in EFAs. Signs include scaly dermatitis, alopecia, thrombocytopenia, and, in children, intellectual disability. Diagnosis is clinical. Dietary replenishment of EFAs reverses the deficiency.
For EFA deficiency to develop, dietary intake must be very low. Even small amounts of EFAs can prevent EFA deficiency. Total fat intake of people in many developing countries may be very low, but the fat is often vegetable based, with large amounts of linoleic acid and enough linolenic acid to prevent EFA deficiency.
Babies fed a formula low in linoleic acid, such as a skim-milk formula, can develop EFA deficiency. EFA deficiency used to result from long-term total parenteral nutrition (TPN) if fat was not included. But now, most TPN solutions include fat emulsions to prevent EFA deficiency. In patients with fat malabsorption or increased metabolic needs (eg, because of surgery, multiple trauma, or burns), laboratory evidence of EFA deficiency may be present without clinical signs.
General Biochemical and Physical Signs and Symptoms of Essential Fatty Acid Deficiency:
- Elevated Triene/Tetraene (T/T) ratio
- Elevated liver function tests
- Altered platelet aggregation
- Dry, scaly rash
- Hair loss
- Hair depigmentation
- Poor wound healing
- Growth restriction in children
- Increased susceptibility to infection
< or = 31 days: 0.017-0.083
32 days - 17 years: 0.013-0.050
> or = 18 years: 0.010-0.038
- An elevated ratio shows a relative excess of triene (3 double bonds) compared to tetraene (4 double bonds), which results from essential fatty acid deficiency (=EFAD).
- An elevated triene:tetraene ratio will manifest before any other signs or symptoms of EFAD
- Dietary replenishment of EFAs reverses the deficiency.
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