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Test ID B6PRO Vitamin B6 Profile (PLP and PA), Plasma

Useful For

Determining the overall success of a vitamin B6 supplementation program


Diagnosis and evaluation of hypophosphatasia

Profile Information

Test ID Reporting Name Available Separately Always Performed
PLP Pyridoxal 5-Phosphate (PLP), P Yes Yes
B6PA Pyridoxic Acid (PA), P No Yes

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

Vitamin B6 Profile (PLP and PA), P

Specimen Type

Plasma Heparin

Shipping Instructions

Ship specimen in amber vial to protect from light.

Specimen Required

Patient Preparation:

1. Fasting-overnight (12-14 hours) (infants-draw prior to next feeding).

2. Patient must not ingest vitamin supplements for 24 hours before the specimen is drawn.

Supplies: Amber Frosted Tube, 5 mL (T192)

Collection Container/Tube: Green top (sodium or lithium heparin) or plasma gel separator tube (PST)

Submission Container/Tube: Amber vial (T192)

Specimen Volume: 1 mL

Collection Instructions: Centrifuge at 4° C within 2 hours of draw, then aliquot all plasma into amber vial.

Specimen Minimum Volume

0.75 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Heparin Refrigerated (preferred) 7 days LIGHT PROTECTED
  Frozen  14 days LIGHT PROTECTED

Clinical Information

Vitamin B6 is a complex of 6 vitamers: pyridoxal, pyridoxol, pyridoxamine, and their 5'-phosphate esters. Due to its role as a cofactor in a number of enzymatic reactions, pyridoxal phosphate (PLP) has been determined to be the biologically active form of vitamin B6.


Vitamin B6 deficiency is a potential cause of burning mouth syndrome and a possible potentiating factor for carpal tunnel and tarsal tunnel syndromes. Persons who present chronic, progressive nerve compression disorders may be deficient in vitamin B6 and should be evaluated. Vitamin B6 deficiency is associated with symptoms of scaling of the skin, severe gingivitis, irritability, weakness, depression, dizziness, peripheral neuropathy, and seizures. In the pediatric population, deficiencies have been characterized by diarrhea, anemia, and seizures.


Markedly elevated PLP in conjunction with low levels of pyridoxic acid (PA) are observed in cases of hypophosphatasia, a disorder characterized by low levels of alkaline phosphatase and a range of skeletal abnormalities.

Reference Values


5-50 mcg/L



3-30 mcg/L


Levels for fasting individuals falling in the range of 3 to 30 mcg/L for pyridoxic acid (PA) and 5 to 50 mcg/L for pyridoxal 5-phosphate (PLP) are indicative of adequate nutrition.


The following are interpretative guidelines based upon PLP and PA results:

-If PLP is >100 mcg/L and PA is ≤30:

-The increased pyridoxal 5-phosphate is suggestive of hypophosphatasia. Consider analysis of serum alkaline phosphatase isoenzymes (ALKI / Alkaline Phosphatase, Total and Isoenzymes, Serum) and urinary phosphoethanolamine (AAPD / Amino Acids, Quantitative, Random, Urine)


-If PLP is >100 mcg/L and PA is 31 to 100 mcg/L or PLP is 81 to 100 mcg/L and PA is ≤30 mcg/L:

-The increased pyridoxal 5-phosphate is likely related to dietary supplementation; however a mild expression of hypophosphatasia cannot be excluded. Consider analysis of serum alkaline phosphatase isoenzymes (ALKI / Alkaline Phosphatase, Total and Isoenzymes, Serum) and urinary phosphoethanolamine (AAPD / Amino Acids, Quantitative, Random, Urine).


-If PLP is 51 to 80 mcg/L or PLP is 81 to 100 mcg/L and PA is >30 or PLP is >100 mcg/L and PA is >100 mcg/L:

-The elevated pyridoxal 5-phosphate is likely due to dietary supplementation.

Clinical Reference

1. Kimura M, Kanehira K, Yokoi K: Highly sensitive and simple liquid chromatographic determination in plasma of B6 vitamins, especially pyridoxal 5'-phosphate. J Chromatogr A 1996;722(1-2):296-301

2. Ball GFM: Vitamins: Their Role in the Human Body. Oxford, UK, Blackwell Publishing, 2004, pp 310-325

3. Mackey AD, Davis SR, Gregory JF III: Vitamin B6. In Modern Nutrition in Health and Disease. 10th edition. Edited by ME Shils, M Shike, AC Ross, et al. Philadelphia, PA, Lippincott Williams and Wilkins, 2006, pp 452-461

Day(s) and Time(s) Performed

Monday through Thursday, Sunday; 11:59 p.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


84207-Pyridoxal phosphate (vitamin B6)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
B6PRO Vitamin B6 Profile (PLP and PA), P 95266-3


Result ID Test Result Name Result LOINC Value
61065 Pyridoxic Acid (PA), P 1688-1
4047 Pyridoxal 5-Phosphate (PLP), P 30552-4

Analytic Time

1 day