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Organic Acids, Quantitative, Full Panel
Test Summary
Clinical Use

  • Diagnose organic acidurias

Clinical Background

Organic acidurias are inherited disorders resulting from a deficient enzyme or transport protein. Although most are autosomal recessive disorders, several are X-linked. The more than 60 described organic acidurias affect many metabolic pathways including amino acid metabolism, lipid metabolism, purine and pyrimidine metabolism, the urea cycle, the Krebs cycle, and fatty acid oxidation. These disorders are characterized by a wide variety of symptoms such as lethargy, coma, hypotonia, seizures, ataxia, vomiting, failure to thrive, developmental delay, liver disease, neutropenia, thrombocytopenia, osteomalacia, and osteoporosis. Severity of presentation is highly variable as is age of onset, and patients may not present with the most characteristic features. Laboratory results commonly indicate metabolic acidosis, increased anion gap, hyperammonemia, hypoglycemia, lactic acidemia, ketosis, or abnormal lipid patterns. Treatment may be based on dietary restrictions and/or supplementation with cofactors (e.g., riboflavin or cobalamin) or conjugating agents (e.g., carnitine or sodium benzoate); however, there is no effective therapy for some of the disorders.

Individuals Suitable For Testing

  • Infants

  • Children

  • Adults

Specimen Requirements

15 mL frozen random urine (no preservatives), 5 mL minimum

Freeze specimen within 4 hours of collection. Avoid bacterial and fecal contamination. Collect urine specimens when the patient is expressing symptoms. Provide a brief clinical history, tentative diagnosis, and therapy over the last 3 days (drugs, X-rays, infant formula, diet).

Method

  • Gas chromatography/mass spectrometry

  • Quantitates 76 organic acids 

  • Reported results: mmol/mol creatinine and a patient specific interpretation

  • Turn-around-time: 4-6 days

  • CPT code*:  83918

Reference Ranges

Reference ranges for each organic acid are provided on the report.

Interpretive Information

Elevation of one or more organic acids is diagnostic for an organic aciduria; however, elevations should be interpreted in context with clinical findings and/or additional test results.

Since many organic acidurias are episodic, the diagnostic efficacy is maximized when the patient is expressing symptoms at the time of specimen collection.

Table. Selected Organic Acidurias and Associated Organic Acid Elevations

Organic Aciduria

Elevated Organic Acid

Methylmalonic acidemia

Methylmalonic acid, methylcitric acid,
3-hydroxypropionic acid, propionylglycine,
3-hydroxyvaleric acid

Fatty oxidation defects (medium chain acyl-CoA dehydrogenase deficiency [MCAD])

Adipic acid, suberic acid, sebacic acid, octanoic acid, suberylglycine, hexanoylglycine, octenedioic acid, phenylpropionylglycine, 5-hydroxyhexanoic acid

Propionic acidemia

Propionylglycine, methylcitric acid,
3-hydroxypropionic acid, 3-hydroxyvaleric acid

Glutaric aciduria, type 1

Glutaric acid, glutaconic acid, 3-hydroxyglutaric acid

Multiple acyl-CoA dehydrogenase deficiency (glutaric aciduria, type II)

Glutaric acid, adipic acid, suberic acid,
2-hydroxyglutaric acid, ethylmalonic acid, isovalerylglycine

Isovaleric acidemia

Isovalerylglycine, 3-hydroxyisovaleric acid

Multiple carboxylase deficiency

3-Methylcrotonylglycine, methylcitric acid, lactic
acid, 3-hydroxyisovaleric acid, tiglylglycine,
3-hydroxypropionic acid

Urea cycle defects

Orotic acid

Maple syrup urine disease (MSUD)

2-Oxoisocaproic acid, 2-hydroxyisocaproic acid,
2-hydroxyisovaleric acid, 2-oxoisovaleric acid,
2-hydroxy-3-methylvaleric acid,
2-oxo-3-methylvaleric acid

Lactic acidosis

Lactic acid, pyruvic acid, 2-hydroxybutyric acid,
4-hydroxyphenyllactic acid

Tyrosinemia

4-Hydroxyphenyllactic acid, 4-hydroxyphenylacetic acid, 4-hydroxyphenylpyruvic acid, N-acetyltyrosine, succinylacetone (type I only)

Canavan disease

N-acetylaspartic acid

Ketosis

Acetoacetic acid, 3-hydroxybutyric acid, adipic acid, suberic acid, 3-hydroxyisobutyric acid,
3-hydroxyisovaleric acid, 3-hydroxy-2-methylbutyric acid

Phenylketonuria (PKU)

Phenyllactic acid, phenylpyruvic acid,
2-hydroxyphenylacetic acid

2-Oxoadipic aciduria

2-Oxoadipic acid, 2-hydroxyadipic acid

3-Hydroxy-3-methylglutaric aciduria

3-Hydroxy-3-methylglutaric acid, 3-hydroxyisovaleric acid, 3-methylcrotonylglycine, 3-methylglutaconic
acid, 3-methylglutaric acid

3-Methylcrotonyl-CoA carboxylase deficiency

3-Hydroxyisovaleric acid, 3-methylcrotonylglycine

3-Methylglutaconic aciduria

3-Methylglutaconic acid, 3-hydroxyisovaleric acid,
3-methylglutaric acid

3-Oxothiolase deficiency

3-Hydroxy-2-methylbutyric acid, tiglylglycine,

2-methylacetoacetic acid, acetoacetic acid,

3-hydroxybutyric acid

5-Oxoprolinuria

5-Oxoproline

Dihydrolipoyl dehydrogenase deficiency (lipoamide dehydrogenase, E3)

Lactic acid, 2-hydroxyisocaproic acid,
2-hydroxyisovaleric acid, 2-hydroxy-3-methylvaleric acid, 2-oxoglutaric acid, 2-oxoisocaproic acid,
2-oxoisovaleric acid, 2-oxo-3-methylvaleric acid
 

References

  1. Part 6, Organic Acids. In Scriver CR, Beaudet AL, Sly WS, et al, eds. The Metabolic and Molecular Basis of Inherited Disease. 7th ed. New York, NY: McGraw-Hill, Inc; 1995:1371-1652.

  2. Sweetman L. Organic Acid Analysis. In Hommes FA, ed. Techniques in Diagnostic Human Biochemical Genetics: A Laboratory Manual. New York, NY: Wiley-Liss; 1991:143-176.
     
*The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.
Content reviewed 11/2006
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