Test ID: POX
Fatty Acid Profile, Peroxisomal (C22-C26), Serum
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Evaluating patients with possible peroxisomal disorders, including peroxisomal biogenesis disorders, X-linked adrenoleukodystrophy, and Refsum disease
Aid in the assessment of peroxisomal function
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
Reports include concentrations of C22:0, C24:0, C26:0 species, phytanic acid and pristanic acid, and calculated C24:0/C22:0, C26:0/C22:0, and phytanic acid/pristanic acid ratios.
Method Name A short description of the method used to perform the test
Gas Chromatography-Mass Spectrometry (GC-MS) Stable Isotope Dilution Analysis
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Adrenomyeloneuropathy
C22-C26, Fatty Acid Profile, Peroxisomal
Cerebrohepatorenal Syndrome
Long-Chain Fatty Acids (LCFA)
Peroxisomal, Fatty Acid Profile
Phytanic Acid
Phytanic Acid Oxidase Deficiency
Pristanic Acid
Refsum Disease
Very Long Chain Fatty Acids (VLCFA)
X-ALD (X-Linked Adrenoleukodystrophy)
X-Linked Adrenoleukodystrophy (X-ALD)
Zellweger Syndrome
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions:
1. Fasting-overnight (12-14 hours).
2. Patient must not consume any alcohol for 24 hours before the specimen is drawn.
3. Spin down within 45 minutes of draw.
Additional Information:
1. Patient's age is required.
2. Include information regarding treatment, family history, and tentative diagnosis.
Forms: If not ordering electronically, submit a Biochemical Genetics Request Form (Supply T439) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross OK |
| Lipemia | Mild reject; Gross reject |
| Icterus | Mild OK; Gross OK |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Frozen (preferred) | 90 days |
| Refrigerated | 24 hours |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Peroxisomes are organelles present in all human cells except mature erythrocytes. They carry out essential metabolic functions including beta-oxidation of very long-chain fatty acids (VLCFA), alpha-oxidation of phytanic acid, and biosynthesis of plasmalogen and bile acids. Peroxisomal disorders include disorders of peroxisomal biogenesis with defective assembly of the entire organelle and single peroxisomal enzyme/transporter defects where the organelle is intact but a specific function is disrupted. Peroxisomal beta-oxidation of VLCFA is impaired in all disorders of peroxisomal biogenesis and in selected single enzyme deficiencies, particularly X-linked adrenoleukodystrophy (X-ALD), resulting in elevated concentrations of VLCFA in plasma.
Peroxisomal biogenesis disorders (PBD) include the Zellweger syndrome spectrum disorders that are clinically diverse and range in severity from neonatal lethal (Zellweger syndrome) to more variable clinical courses in neonatal adrenoleukodystrophy and infantile Refsum disease. Affected children typically have hypotonia, poor feeding, distinctive facial features, seizures, and liver dysfunction. Other features can include retinal dystrophy, hearing loss, developmental delays, and bleeding episodes. Rhizomelic chondrodysplasia punctata is another PBD. It is characterized by rhizomelic shortening, chondrodysplasia punctata, cataracts, intellectual disability, and seizures, although it can have a milder phenotype with only cataracts and chondrodysplasia. The typical biochemical profile shows normal VLCFA and elevated phytanic acid.
X-ALD is a neurologic disorder affecting the white matter and adrenal cortex. It can present between ages 4 and 8 as a childhood cerebral form with behavioral and cognitive changes, associated with neurologic decline. Other forms include an "Addison disease only" phenotype with adrenocortical insufficiency without initial neurologic abnormality and adrenomyeloneuropathy associated with later-onset progressive paraparesis. X-ALD is an X-linked condition that primarily affects males; however, some females who are carriers can develop later-onset neurologic manifestations.
Refsum disease is a peroxisomal disorder characterized by anosmia, retinitis pigmentosa, neuropathy, deafness, ataxia, ichthyosis, and cardiac abnormalities. The classic biochemical profile of Refsum disease is an elevated plasma phytanic acid level.
Biochemical abnormalities in peroxisomal disorders include accumulations of VLCFA, phytanic, and pristanic acid. The differential diagnosis of these disorders is based on recognition of clinical phenotypes combined with a series of biochemical tests to assess peroxisomal function and structure. These include measurements and ratios of VLCFA, pipecolic acid (PIPA/81326 Pipecolic Acid, Serum; PIPU/81248 Pipecolic Acid, Urine), phytanic acid and its metabolite pristanic acid.
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.
C22:0
< or =96.3 nmol/mL
C24:0
< or =91.4 nmol/mL
C26:0
< or =1.30 nmol/mL
C24:0/C22:0 RATIO
< or =1.39
C26:0/C22:0 RATIO
< or =0.023
PRISTANIC ACID
0-4 months: < or =0.60 nmol/mL
5-8 months: < or =0.84 nmol/mL
9-12 months: < or =0.77 nmol/mL
13-23 months: < or =1.47 nmol/mL
> or =24 months: < or =2.98 nmol/mL
PHYTANIC ACID
0-4 months: < or =5.28 nmol/mL
5-8 months: < or =5.70 nmol/mL
9-12 months: < or =4.40 nmol/mL
13-23 months: < or =8.62 nmol/mL
> or =24 months: < or =9.88 nmol/mL
PRISTANIC/PHYTANIC ACID RATIO
0-4 months: < or =0.35
5-8 months: < or =0.28
9-12 months: < or =0.23
13-23 months: < or =0.24
> or =24 months: < or =0.39
Interpretation Provides information to assist in interpretation of the test results
Reports include concentrations of C22:0, C24:0, C26:0 species, phytanic acid and pristanic acid, and calculated C24:0/C22:0, C26:0/C22:0, and phytanic acid:pristanic acid ratios. When no significant abnormalities are detected, a simple descriptive interpretation is provided.
A profile of elevated phytanic acid, low-normal pristanic acid, and normal very long-chain fatty acids is suggestive of Refsum disease (phytanic acid oxidase deficiency); however, serum phytanic acid concentration may also be increased in disorders of peroxisomal biogenesis and should be considered in the differential diagnosis of peroxisomal disorders.
If results are suggestive of hemizygosity for X-linked adrenoleukodystrophy, we also include the calculated value of a discriminating function used to more accurately segregate hemizygous individuals from normal controls.
Positive test results could be due to genetic or nongenetic condition. Additional confirmatory testing would be required.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
In rare instances, patients with X-linked adrenoleukodystrophy (X-ALD) may have only minimally elevated values; 15% to 20% of women heterozygous for X-ALD have normal plasma very long-chain fatty acid levels.
False-positive results may occur with nonfasting specimens.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Moser AB, Kreiter N, Bezman L, et al: Plasma very long chain fatty acid assay in 3,000 peroxisome disease patients and 29,000 controls. Ann Neurol 1999;45:100-110
2. Wanders RJA: Inborn Errors of Peroxisome Biogenesis and Function. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou, GF Hoffmann, KS Roth, New York, NY, McGraw-Hill Medical Division, 2009, pp 323-337
Method Description Describes how the test is performed and provides a method-specific reference
Acidic hydrolysis is followed by basic hydrolysis and reacidification. Hexane extraction then proceeds to derivatization with pentafluorobenzyl bromide (PFB). Separation and detection of PFB-esters is accomplished by capillary gaschromatograph-mass spectrometry using electron capture ionization and selected negative ion monitoring. Quantitation is enhanced by the use of stable isotope-labeled internal standards. (Stellard F, ten Brink HJ, Kok RM, et al: Stable isotope dilution analysis of very long chain fatty acids in plasma, urine and amniotic fluid by electron capture negative ion mass fragmentography. Clin Chim Acta1990;192:133-144)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 9 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
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 The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
82726
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 81369 | C22:0 | 30194-5 |
| 7143 | C24:0 | 30195-2 |
| 7137 | C26:0 | 30197-8 |
| 7138 | C24:0/C22:0 | 30196-0 |
| 7139 | C26:0/C22:0 | 30198-6 |
| 7140 | Pristanic Acid | 22761-1 |
| 7141 | Phytanic Acid | 22671-2 |
| 7142 | Pristanic/Phytanic | 30550-8 |
| 7144 | Comment | 48767-8 |
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