Vitamin B6 (pyridoxal-5’-phospate, PLP)

Description: 
PLP can be measured either in serum, plasma or whole blood. All are valid matrices for the assessment of B6 status in many patients. However, serum and plasma PLP concentrations are subject to changes in acute phase response. Because of this, it is preferable that PLP is measured in whole blood. A Gerstel Multi Purpose Sampler coupled with liquid chromatography and electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) is used for the analysis of pyridoxal-5’-phosphate.

This test is not currently included in the laboratory's UKAS scope of accreditation to ISO15189:2012
Clinical details: 
Vitamin B6 in food can be found mainly as the three 5’-phosphate ester forms with particularly high concentrations in yeast extract, wheat bran and liver. Once absorbed vitamin B6 is transported to the liver where the various forms are converted to the physiologically active form, pyridoxal-5’-phosphate (PLP), by pyridoxal kinase. The roles of vitamin B6 in the human body include; amino acid metabolism, homocysteine metabolism, porphyrin biosynthesis, nucleic acid biosynthesis, glycogenolysis, lipid metabolism, steroid hormone regulation and maintenance of the immune system. Symptoms of deficiency are thought to be gastrointestinal disturbances and epithelial changes. However as B6 is so widespread in foods it would be expected that deficiency in B6 would be accompanied by a concomitant deficiency in other water soluble vitamins thus making it difficult to differentiate between the symptoms of the various deficiencies. High vitamin B6 intake is known to be toxic.
Reference range: 

44-168 nmol/L

Synonyms or keywords: 
Pyridoxal; Pyridoxal-5'-phosphate
Units: 
nmol/L
Sample type and Volume required: 
200μL of EDTA whole blood or EDTA plasma/SST serum
Call in advance: 
No
Turnaround time: 
10 days
Special sample instructions: 

Protect specimens from light and store frozen at -20 degrees, transport on ice.

Storage and transport: 
Transport on ice
Contacts:
Nutristasis Unit at St Thomas'
020 7188 6815 / 89543
St Thomas' Hospital
North Wing - 4th Floor
Westminster Bridge Road
London SE1 7EH

Laboratory opening times
Monday - Friday 09.00 - 17.00
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

Print as a PDF

Last updated: 02/11/2023