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Test Code LAB4373 Acylcarnitines, Quantitative, Plasma

Additional Codes

Test Name in EPIC EPIC Test Code Mnemonic Mayo Test ID
ACYLCARNITINES,
QUANTITATIVE, P		 LAB4373 ACRN ACRN

 

Reporting Name

Acylcarnitines, Quantitative, P

Useful For

Diagnosis of fatty acid oxidation disorders and several organic acidurias using plasma specimens

 

Evaluating treatment during follow-up of patients with fatty acid beta-oxidation disorders and several organic acidurias

Method Name

Flow Injection Analysis-Tandem Mass Spectrometry (FIA-MS/MS)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Plasma


Necessary Information


1. Patient's age is required.

2. Include family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information.



Specimen Required


Patient Preparation: Collect specimen just prior to a scheduled meal or feeding.

Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: Lavender top (EDTA) or green top (lithium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: 0.1 mL

Collection Instructions: Centrifuge and aliquot plasma into plastic vial.


Specimen Minimum Volume

0.04 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Frozen (preferred) 92 days
  Refrigerated  64 days
  Ambient  8 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Reference Values

≤7 days (nmol/mL)

8 days-7 years (nmol/mL)

≥8 years (nmol/mL)

Acetylcarnitine, C2

2.14-15.89

2.00-27.57

2.00-17.83

Acrylylcarnitine, C3:1

<0.04

<0.05

<0.07

Propionylcarnitine, C3

<0.55

<1.78

<0.88

Formiminoglutamate, FIGLU

<0.43

<0.08

<0.14

Iso-/Butyrylcarnitine, C4

<0.46

<1.06

<0.83

Tiglylcarnitine, C5:1

<0.05

<0.09

<0.11

Isovaleryl-/2-Methylbutyrylcarn C5

<0.38

<0.63

<0.51

3-OH-iso-/butyrylcarnitine, C4-OH

<0.13

<0.51

<0.18

Hexenoylcarnitine, C6:1

<0.12

<0.10

<0.15

Hexanoylcarnitine, C6

<0.14

<0.23

<0.17

3-OH-isovalerylcarnitine, C5-OH

<0.08

<0.12

<0.10

Benzoylcarnitine

<0.13

<0.07

<0.10

Heptanoylcarnitine, C7

<0.05

<0.05

<0.06

3-OH-hexanoylcarnitine, C6-OH

<0.08

<0.19

<0.09

Phenylacetylcarnitine

<0.15

<0.22

<0.29

Salicylcarnitine

<0.08

<0.09

<0.09

Octenoylcarnitine, C8:1

<0.48

<0.91

<0.88

Octanoylcarnitine, C8

<0.19

<0.45

<0.78

Malonylcarnitine, C3-DC

<0.09

<0.14

<0.26

Decadienoylcarnitine, C10:2

<0.11

<0.12

<0.26

Decenoylcarnitine, C10:1

<0.25

<0.46

<0.47

Decanoylcarnitine, C10

<0.27

<0.91

<0.88

Methylmalonyl-/succinylcarn, C4-DC

<0.05

<0.05

<0.05

3-OH-decenoylcarnitine, C10:1-OH

<0.12

<0.12

<0.13

Glutarylcarnitine, C5-DC

<0.06

<0.10

<0.11

Dodecenoylcarnitine, C12:1

<0.19

<0.37

<0.35

Dodecanoylcarnitine, C12

<0.18

<0.35

<0.26

3-Methylglutarylcarnitine, C6-DC

<0.28

<0.21

<0.43

3-OH-dodecenoylcarnitine, C12:1-OH

<0.11

<0.10

<0.13

3-OH-dodecanoylcarnitine, C12-OH

<0.06

<0.09

<0.08

Tetradecadienoylcarnitine, C14:2

<0.09

<0.13

<0.18

Tetradecenoylcarnitine, C14:1

<0.16

<0.35

<0.24

Tetradecanoylcarnitine, C14

<0.11

<0.15

<0.12

Octanedioylcarnitine, C8-DC

<0.25

<0.19

<0.19

3-OH-tetradecenoylcarnitine C14:1OH

<0.06

<0.18

<0.13

3-OH-tetradecanoylcarnitine, C14-OH

<0.04

<0.05

<0.08

Hexadecenoylcarnitine, C16:1

<0.15

<0.21

<0.10

Hexadecanoylcarnitine, C16

<0.36

<0.52

<0.23

3-OH-hexadecenoylcarnitine,C16:1-OH

<0.78

<0.36

<0.06

3-OH-hexadecanoylcarnitine, C16-OH

<0.10

<0.07

<0.06

Octadecadienoylcarnitine, C18:2

<0.12

<0.31

<0.24

Octadecenoylcarnitine, C18:1

<0.25

<0.45

<0.39

Octadecanoylcarnitine, C18

<0.10

<0.12

<0.14

Dodecanedioylcarnitine, C12-DC

<0.10

<0.04

<0.04

3-OH-octadecadienoylcarn, C18:2-OH

<0.04

<0.06

<0.06

3-OH-octadecenoylcarnitine C18:1-OH

<0.03

<0.04

<0.06

3-OH-octadecanoylcarnitine, C18-OH

<0.03

<0.05

<0.03

Day(s) Performed

Monday through Friday

CPT Code Information

82017

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ACRN Acylcarnitines, Quantitative, P 43433-2

 

Result ID Test Result Name Result LOINC Value
82413 Acylcarnitines, Quantitative, P 46252-3
10288 Acetylcarnitine, C2 30191-1
36497 Acrylylcarnitine, C3:1 43235-1
10289 Propionylcarnitine, C3 30551-6
36498 Formiminoglutamate, FIGLU 79628-4
10290 Iso-/Butyrylcarnitine, C4 43243-5
36499 Tiglylcarnitine, C5:1 51416-6
10293 Isovaleryl-/2-Methylbutyrylcarn C5 30531-8
36500 3-OH-iso-/butyrylcarnitine, C4-OH 39000-5
36501 Hexenoylcarnitine, C6:1 74540-6
10295 Hexanoylcarnitine, C6 30358-6
36502 3-OH-isovalerylcarnitine, C5-OH 39001-3
36503 Benzoylcarnitine 39615-0
36504 Heptanoylcarnitine, C7 55871-8
10297 3-OH-hexanoylcarnitine, C6-OH 30236-4
36505 Phenylacetylcarnitine 90237-9
36506 Salicylcarnitine 90238-7
10298 Octenoylcarnitine, C8:1 30541-7
10299 Octanoylcarnitine, C8 30540-9
36507 Malonylcarnitine, C3-DC 55940-1
36508 Decadienoylcarnitine, C10:2 53471-9
10301 Decenoylcarnitine, C10:1 30328-9
10302 Decanoylcarnitine, C10 30327-1
36509 Methylmalonyl-/succinylcarn, C4-DC 51415-8
36510 3-OH-decenoylcarnitine, C10:1-OH 82478-9
10304 Glutarylcarnitine, C5-DC 30349-5
10305 Dodecenoylcarnitine, C12:1 30332-1
10306 Dodecanoylcarnitine, C12 30331-3
36511 3-Methylglutarylcarnitine, C6-DC 39002-1
36512 3-OH-dodecenoylcarnitine, C12:1-OH 59195-8
10307 3-OH-dodecanoylcarnitine, C12-OH 30233-1
10308 Tetradecadienoylcarnitine, C14:2 30564-9
10309 Tetradecenoylcarnitine, C14:1 30566-4
10310 Tetradecanoylcarnitine, C14 30565-6
36513 Octanedioylcarnitine, C8-DC 39014-6
10311 3-OH-tetradecenoylcarnitine C14:1OH 30190-3
10312 3-OH-tetradecanoylcarnitine, C14-OH 30238-0
10313 Hexadecenoylcarnitine, C16:1 30357-8
10314 Hexadecanoylcarnitine, C16 30356-0
10315 3-OH-hexadecenoylcarnitine,C16:1-OH 30235-6
10316 3-OH-hexadecanoylcarnitine, C16-OH 30234-9
10317 Octadecadienoylcarnitine, C18:2 30534-2
10318 Octadecenoylcarnitine, C18:1 30542-5
10319 Octadecanoylcarnitine, C18 30560-7
36514 Dodecanedioylcarnitine, C12-DC 55855-1
10320 3-OH-octadecadienoylcarn, C18:2-OH 30237-2
10321 3-OH-octadecenoylcarnitine C18:1-OH 30312-3
36515 3-OH-octadecanoylcarnitine, C18-OH 35656-8
10322 Comment (ACRN) 48767-8

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.

Clinical Information

Acylcarnitine analysis enables the diagnosis of many disorders of fatty acid oxidation and several organic acidurias, as relevant enzyme deficiencies cause the accumulation of specific acyl-CoAs.(1) Fatty acid oxidation (FAO) plays a major role in energy production during periods of fasting. When the body's supply of glucose is depleted, fatty acids are mobilized from adipose tissue, taken up by the liver and muscles, and oxidized to acetyl-CoA. In the liver, acetyl-CoA is the building block for the synthesis of ketone bodies, which enter the blood stream and provide an alternative substrate for production of energy in other tissues when the supply of glucose is insufficient to maintain a normal level of energy. The acyl groups are conjugated with carnitine to form acylcarnitines, which can be measured by tandem mass spectrometry. Diagnostic results are usually characterized by a pattern of significantly elevated acylcarnitine species compared to normal and disease controls.

 

In general, more than 20 inborn errors of metabolism can be identified using this method, including FAO disorders and organic acidurias. The major clinical manifestations associated with individual FAO disorders include hypoketotic hypoglycemia, variable degrees of liver disease and failure, skeletal myopathy, dilated/hypertrophic cardiomyopathy, and sudden or unexpected death. Organic acidurias also present as acute life-threatening events early in life with metabolic acidosis, increased anion gap, and neurologic distress. Patients with any of these disorders are at risk of developing fatal metabolic decompensations following the acquisition of even common infections. Once diagnosed, these disorders can be treated by avoidance of fasting, special diets, and cofactor and vitamin supplementation.

 

Additional confirmatory testing is recommended. The diagnosis of an underlying FAO disorder or organic aciduria allows genetic counseling of the family, including the possible option of future prenatal diagnosis, and testing of at-risk family members of any age.

 

The following disorders are detectable by acylcarnitine analysis. However, further confirmatory testing is required for most of these conditions because an acylcarnitine profile can be suggestive of more than one condition.

 

Fatty Acid Oxidation Disorders:

-Carnitine palmitoyltransferase I deficiency

-Medium-chain 3-ketoacyl-CoA thiolase deficiency

-Dienoyl-CoA reductase deficiency

-Short-chain acyl-CoA dehydrogenase deficiency

-Medium/Short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

-Medium-chain acyl-CoA dehydrogenase deficiency

-Long-chain 3-hydroxyacyl-CoA dehydrogenase) deficiency and trifunctional protein deficiency

-Very long-chain acyl-CoA dehydrogenase deficiency

-Carnitine palmitoyl transferase type II deficiency

-Carnitine-acylcarnitine translocase deficiency

-Electron transfer flavoprotein (ETF) deficiency, ETF-dehydrogenase deficiency (multiple acyl-CoA dehydrogenase deficiency; glutaric acidemia type II)

 

Organic Acid Disorders:

-Glutaryl-CoA dehydrogenase deficiency (glutaric acidemia type I)

-Propionic acidemia

-Methylmalonic acidemia

-Isovaleric acidemia

-3-Hydroxy-3-methylglutaryl-CoA carboxylase deficiency

-3-Methylcrotonyl carboxylase deficiency

-Biotinidase deficiency

-Multiple carboxylase deficiency

-Isobutyryl-CoA dehydrogenase deficiency

-2-Methylbutyryl-CoA dehydrogenase deficiency

-Beta-ketothiolase deficiency

-Malonic aciduria

-Ethylmalonic encephalopathy

-Glutamate formiminotransferase deficiency (formiminoglutamic aciduria)

Interpretation

An interpretive report is provided. The individual quantitative results support the interpretation of the acylcarnitine profile but are not diagnostic by themselves. The interpretation is based on pattern recognition.

 

Abnormal results are typically not sufficient to conclusively establish a diagnosis of a particular disease. To verify a preliminary diagnosis based on an acylcarnitine analysis, independent biochemical or molecular genetic analyses are required.

Cautions

In a few instances, false-negative results occur in the analysis of acylcarnitine profiles. For some disorders, such as medium-chain acyl-CoA dehydrogenase deficiency, the calculation of ratios between different acylcarnitine species provides a discriminate factor to overcome such problems. Where applicable, the calculation of such ratios will be incorporated in the routine acylcarnitine analysis. Informative profiles may also not be detected in some disorders where the accumulation of diagnostic acylcarnitines is a reflection of the residual activity of the defective enzyme, the dietary load of precursors, and the anabolic/catabolic and treatment status of a patient.

 

Patients with carnitine deficiency may not exhibit abnormally high acylcarnitine concentrations. If the results are indicative for carnitine deficiency, the interpretation will include a remark that this limits the diagnostic value of the test and repeat analysis may be considered following carnitine supplementation.

 

Follow-up testing such as in vitro enzyme assays or molecular genetic testing may be recommended following abnormal acylcarnitine results. It is not advisable to intentionally stress the patient's metabolism (eg, fasting test) prior to specimen collection for acylcarnitine analysis.

Method Description

Six internal standards of known concentration (d3-acetylcarnitine, d3-propionylcarnitine, d7-butyrylcarnitine, d3-octanoylcarnitine, d3-dodecanoylcarnitine, and d3-palmitoyl-carnitine) and acetonitrile for deproteinization are added to plasma. The supernate is dried and then treated with n-butanolic HCl yielding the acylcarnitines, which are analyzed as their n-butylesters by electrospray ionization tandem mass spectrometry. The concentrations of the analytes are established by computerized comparison of these analytes' ion intensities to those of the closest internal standard.(Van Hove JL, Kahler SG, Feezor MD, et al. Acylcarnitines in plasma and blood spots of patients with long-chain 3-hydroxyacylcoenzyme A dehydrogenase deficiency. J Inherit Metab Dis. 2000;23:571-582; Miller MJ, Cusmano-Ozog K, Oglesbee D, Young S; ACMG Laboratory Quality Assurance Committee. Laboratory analysis of acylcarnitines, 2020 update: a technical standard of the American College of Medical Genetics and Genomics [ACMG]. Genet Med. 2021;23[2]:249-258)

Report Available

2 to 5 days

Specimen Retention Time

1 month