Test Id : PLP
Pyridoxal 5-Phosphate, Plasma
Useful For
Suggests clinical disorders or settings where the test may be helpful
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
A short description of the method used to perform the test
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
B6 (Vitamin)
PALP (Pyridoxal 5-Phosphate)
Pyridoxal 5-Phosphate (PALP)
Pyridoxal Phosphate
Vitamin B6
Specimen Type
Describes the specimen type validated for testing
Plasma Heparin
Shipping Instructions
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
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 degrees C.
2. Aliquot all plasma into amber vial and freeze immediately.
Forms
If not ordering electronically, complete, print, and send a General Request (T239) with the specimen.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
0.75 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Heparin | Frozen | 29 days | LIGHT PROTECTED |
Useful For
Suggests clinical disorders or settings where the test may be helpful
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
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Vitamin B6 is a generic term that refers to the pyridine-based compounds pyridoxine, 4-pyridoxic acid (PA), pyridoxamine, pyridoxal, and their phosphorylated derivatives. Pyridoxal-5'-phosphate (PLP) is the biologically active form and serves as a cofactor for more than 140 different enzyme reactions, representing 4% of all known catalytic activity. Deficiencies can occur in people with mutations of pyridoxal kinase (PLK) or pyridoxine 5' phosphate oxidase (PNPOx), as well as in individuals who are pregnant, have kidney disease, are severely malnourished, or have malabsorption. Additionally, deficiencies have been observed with the usage of certain drugs such as isoniazid, penicillamine, benserazide, and carbidopa. 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. Conversely, exceptionally high levels of vitamin B6 can also have toxic effects resulting in sensory and motor neuropathies. Markedly elevated PLP in conjunction with low or normal levels of pyridoxic acid are observed in cases of hypophosphatasia, a disorder caused by loss-of-function mutations of the gene ALPL that encodes the tissue-nonspecific isoenzyme of alkaline phosphatase.
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
5-50 mcg/L
Interpretation
Provides information to assist in interpretation of the test results
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 < or =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.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Reference ranges were established using healthy fasting volunteers who abstained from vitamin supplementation for 24 hours prior to collection. Vitamin supplementation and nonfasting may result in elevated plasma vitamin concentrations.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
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
Method Description
Describes how the test is performed and provides a method-specific reference
The stable isotope pyridoxal 5-phosphate-d2 and/or pyridoxic acid-d2 is added to plasma as an internal standard. Meta-phosphoric acid solution is then added to precipitate the proteins. Following sedimentation of the proteins, an aliquot of the clarified supernatant fluid is subjected to separation of pyridoxal 5-phosphate, pyridoxic acid, and internal standards from other plasma components by reverse-phase high-performance liquid chromatography with quantitation by tandem mass spectrometry.(Maus A, Girtman A, Kiesling J, Faber J, Grebe SKG. Overcoming the chromatographic challenges when performing LC-MS/MS measurements of pyridoxal-5'-phosphate. J Chromatogr B Analyt Technol Biomed Life Sci. 2023;1217:123605. doi:10.1016/j.jchromb.2023)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday through Thursday, Saturday, Sunday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
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- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
84207
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| PLP | Pyridoxal 5-Phosphate (PLP), P | 30552-4 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| 4047 | Pyridoxal 5-Phosphate (PLP), P | 30552-4 |