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Test ID: FAPM    
Fatty Acid Profile, Mitochondrial (C8-C18), Serum

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Useful For Suggests clinical disorders or settings where the test may be helpful

Biochemical diagnosis of inborn errors of mitochondrial fatty acid oxidation, including deficiencies of medium-chain acyl-Co-A dehydrogenase, long-chain 3-hydroxyacyl-Co-A dehydrogenase, very long-chain acyl-Co-A dehydrogenase, and glutaricacidemia type 2.

Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request

Biochemical diagnosis of inborn errors of mitochondrial fatty acid oxidation

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Mitochondrial beta-oxidation is the main source of energy to skeletal and heart muscle during periods of fasting. When the body's supply of glucose is depleted, fatty acids are mobilized from adipose tissue and converted to ketone bodies thorough a series of steps providing an alternate source of energy. Deficient enzymes at any step in this pathway prevent the production of energy during periods of physiologic stress such as fasting or intercurrent illness.

 

The major clinical manifestations associated with fatty acid oxidation (FAO) disorders include hypoketotic hypoglycemia, liver disease and failure, skeletal myopathy, dilated/hypertrophic cardiomyopathy, and sudden unexpected death in early life. Signs and symptoms may vary greatly in severity, combination and age of presentation. Life-threatening episodes of metabolic decompensation frequently occur after periods of inadequate calorie intake or intercurrent illness. When properly diagnosed, patients with FAO disorders respond favorably to fasting avoidance, diet therapy, and aggressive treatment of intercurrent illnesses, with significant reduction of morbidity and mortality.

 

Disease-specific characteristic patterns of metabolites from FAO disorders are detectable in blood, bile, urine, and cultured fibroblasts of living and many deceased individuals. Quantitative determination of C8-C18 fatty acids is an important element of the work-up and differential diagnosis of candidate patients. Fatty acid profiling can detect quantitatively modest, but nevertheless significant, abnormalities even when patients are asymptomatic and under dietary treatment. Enzyme and molecular confirmatory testing is also available for many of the FAO disorders at Mayo Medical Laboratories.

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.

Octanoic Acid, C8:0

<1 year: 7-63 nmol/mL

1-17 years: 9-41 nmol/mL

> or =18 years: 8-47 nmol/mL

 

Decenoic Acid, C10:1

<1 year: 0.8-4.8 nmol/mL

1-17 years: 1.6-6.6 nmol/mL

> or =18 years: 1.8-5.0 nmol/mL

 

Decanoic Acid, C10:0

<1 year: 2-62 nmol/mL

1-17 years: 3-25 nmol/mL

> or =18 years: 2-18 nmol/mL

 

Lauroleic Acid, C12:1

<1 year: 0.6-4.8 nmol/mL

1-17 years: 1.3-5.8 nmol/mL

> or =18 years: 1.4-6.6 nmol/mL

 

Lauric Acid, C12:0

<1 year: 6-190 nmol/mL

1-17 years: 5-80 nmol/mL

> or =18 years: 6-90 nmol/mL

 

Tetradecadienoic Acid, C14:2

<1 year: 0.3-6.5 nmol/mL

1-17 years: 0.2-5.8 nmol/mL

> or =18 years: 0.8-5.0 nmol/mL

 

Myristoleic Acid, C14:1

<1 year: 1-46 nmol/mL

1-17 years: 1-31 nmol/mL

> or =18 years: 3-64 nmol/mL

 

Myristic Acid, C14:0

<1 year: 30-320 nmol/mL

1-17 years: 40-290 nmol/mL

> or =18 years: 30-450 nmol/mL

 

Hexadecadienoic Acid, C16:2

<1 year: 4-27 nmol/mL

1-17 years: 3-29 nmol/mL

> or =18 years: 10-48 nmol/mL

 

Palmitoleic Acid, C16:1w7

<1 year: 20-1,020 nmol/mL

1-17 years: 100-670 nmol/mL

> or =18 years: 110-1,130 nmol/mL

 

Palmitic Acid, C16:0

<1 year: 720-3,120 nmol/mL

1-17 years: 960-3,460 nmol/mL

> or =18 years: 1,480-3,730 nmol/mL

 

Linoleic Acid, C18:2w6

1-31 days: 350-2,660 nmol/mL

32 days-11 months: 1,000-3,300 nmol/mL

1-17 years: 1,600-3,500 nmol/mL

> or =18 years: 2,270-3,850 nmol/mL

 

Oleic Acid, C18:1w9

<1 year: 250-3,500 nmol/mL

1-17 years: 350-3,500 nmol/mL

> or =18 years: 650-3,500 nmol/mL

 

Stearic Acid, C18:0

<1 year: 270-1,140 nmol/mL

1-17 years: 280-1,170 nmol/mL

> or =18 years: 590-1,170 nmol/mL

Interpretation Provides information to assist in interpretation of the test results

Fatty acid oxidation disorders are recognized on the basis of disease-specific metabolite patterns that are correlated to the results of other investigations in plasma (carnitine, acylcarnitines) and urine (organic acids, acylglycines).

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

For nutritional assessment, a 12- to 14-hour fast is required; however, patients suspected of having a fatty acid oxidation disorder should not fast before testing owing to the possibility of acute metabolic decompensation. Instead, draw the specimen after the longest fast possible, just before feeding.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Stellaard 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 Acta 1990;192:133-144

2. Rinaldo P, Matern D, Bennett MJ: Fatty acid oxidation disorders. Ann Rev Physiol 2002;64:477-502

3. Lagerstedt SA Hinrichs DR, Batt SM, et al: Quantitative determination of plasma C8-C26 total fatty acids for the biochemical diagnosis of nutritional and metabolic disorders. Mol Gen Metab 2001;73(1):38-45