Suitable Specimen Types
- EDTA Whole Blood
Sample Processing in Laboratory
Referring laboratories using the Vitamin B service should note that the sample must arrive at West Park deep frozen, therefore requiring transportation in sufficient dry ice to last 24 hours.
Sample Preparation
Light-protected unhaemolysed whole-blood samples can be stored at 4 degrees for up to 6 hours, however after 6 hours they must be stored at -20 degrees. Referring laboratories using the Vitamin B service should note that the sample must arrive at West Park deep frozen, therefore requiring transportation in sufficient dry ice to last 24 hours. Samples from very local centres can be sent over to West Park cooled on an ice pack provided they arrive within the 6 hour window
Sample stability: samples for Vitamin B1, B2 and B6 are stable for 6 months at -20 degrees.
Turnaround Time
NULLSample Stability
The sample required is EDTA-whole blood (i.e. unseparated) and it must be protected from light (ie wrap it in aluminium foil). Please avoid haemolysis during sample collection as the analytes are more succeptible to analyte degradation until deep froze
Thiamine, Vitamin B1, B2 and B6
General Information
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Patient Preparation
Patients should be fasted and the sample collected in the morning prior to any medication. Avoid measurement of B2 and B6 during a severe acute phase response eg surgery, allowing at least 14 days afterwards.
Notes
Thiamine diphosphate (TDP) also referred to as thiamine pyrophosphate is the physiologically active form of Vitamin B1 that is measured. Similarly Riboflavin, which is mainly converted to flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), is the physiologically active form of Vitamin B2 that is measured. Pyridoxil-5’-phosphate (PLP) is the active coenzyme form of Vitamin B6 that is measured.
Vitamin B1 measures TDP directly whilst the red-cell transketolase measures the increase in transketolase activity after addition of TDP cofactor. Both are equally diagnostic and can be used also for monitoring the disease recovery in such conditions as classic Vitamin B1 deficiency (beriberi), Wernicke’s encephalopathy, Korsakov’s syndrome and several forms of Landry’s paralysis. From June 2005 we have discouraged service users from requesting red-cell transketolase unless there is a particular requirement in which case this must be discussed with the Duty Biochemist. Note that transketolase activity is only stable for up to 2 weeks at -20 degrees.
Reference Range
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Specifications
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EQA Status:
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