Activities of blood transaminases, either aspartate (GOT) or alanine (GPT) aminotransferase, can serve as indications of a patient's vitamin B6 nutritional status. Enzymatic assays run before and after addition of pyridoxal phosphate can be used to generate an activity coefficient ratio. This represents the functional availability of erythrocyte vitamin B6 in its coenzyme form. Its value increases with vitamin B6 deficiency.
Specimen: Whole blood collected in EDTA. Hemolysate prepared which is stable for several weeks at -20 C and for up to 10 weeks at -70 C. Repeated freeze-thaw cycles should be avoided.
Analysis: Erythrocyte glutamate oxaloacetate transaminase (EGOT, aspartate transaminase) is measured in an erythrocyte hemolysate before and after stimulation with pyridoxal phosphate (25 µg/mL) for 20 minutes.
EGOT index =
= (GOT of hemolysate after stimulation with pyridoxal phosphate) / GOT of hemolysate before stimulation with pyridoxal phosphate
where:
• Units for erythrocyte GOT need to be clarified; probably units per gram hemoglobin (alternatives: units per 10^12 erythrocytes).
Interpretation:
• The criteria for interpreting results varies with the amount of pyridoxal phosphate added and with the method of testing.
• vitamin B6 deficiency: > 1.5
• acceptable B6 levels: < 1.5
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