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HelpTest Code PLP Pyridoxal 5-Phosphate, Plasma
Useful For
Determining vitamin B6 status, including in persons who present with progressive nerve compression disorders, such as carpal tunnel and tarsal tunnel syndromes
Determining the overall success of a vitamin B6 supplementation program
Diagnosis and evaluation of hypophosphatasia
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Pyridoxal 5-Phosphate (PLP), PSpecimen Type
Plasma HeparinShipping Instructions
Ship specimen in amber vial to protect from light.
Specimen Required
Patient Preparation:
1. Patient should fast overnight (12-14 hours); infants-should have specimen collected before next feeding. Water can be taken as needed.
2. For 24 hours before specimen collection, patient should not take multivitamins or vitamin supplements.
Supplies: Amber Frosted Tube, 5 mL (T915)
Collection Container/Tube:
Preferred: Green top (sodium or lithium heparin) or Plasma gel separator (PST)
Acceptable: None
Submission Container/Tube: Amber vial
Specimen Volume: 1 mL
Collection Instructions:
1. Within 2 hours of collection, centrifuge at 4° C.
2. Aliquot all plasma into amber vial and freeze immediately.
Specimen Minimum Volume
0.75 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Heparin | Frozen | 29 days | LIGHT PROTECTED |
Reference Values
5-50 mcg/L
Interpretation
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 mcg/L:
-The increased pyridoxal 5-phosphate is suggestive of hypophosphatasia. Consider analysis of serum alkaline phosphatase isoenzymes (ALKP / 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 < or=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 (ALKP / 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 mcg/L; or PLP is >100 mcg/L and PA is >100 mcg/L:
-The elevated PLP is likely due to dietary supplementation.
Clinical Reference
1.Whyte MP, Zhang F, Wenkert D, Mack KE, et al. Hypophosphatasia: Vitamin B6 status of affected children and adults. Bone. 2022;154:116204. doi:10.1016/j.bone.2021.116204
2. Vitamin B6-Fact Sheet for Health Professionals. US Department of Health and Human Services, National Institutes of Health. Office of Dietary Supplements. Updated June 16, 2023. Accessed February 5, 2025.
Available at: https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/
3. Sodi R, Taylor A. Vitamins and trace elements In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics. 8th ed. Elsevier; 2020:466-487
4. Morris MS, Picciano MF, Jacques PF, Selhub J. Plasma pyridoxal 5'-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004. Am J Clin Nutr. 2008;87(5):1446-54. doi:10.1093/ajcn/87.5.1446
5. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Cholineexternal link disclaimer. National Academy Press; 1998
Day(s) Performed
Monday through Thursday, Saturday, Sunday
Report Available
2 to 7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
84207
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PLP | Pyridoxal 5-Phosphate (PLP), P | 30552-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 4047 | Pyridoxal 5-Phosphate (PLP), P | 30552-4 |
Forms
If not ordering electronically, complete, print, and send a General Request (T239) with the specimen.