Organic acids urine

Specimen:

Random urine, collected when patient is acidotic if the test is being done for identification of the cause of metabolic acidosis.

Freeze sample after collection.

Method:

GCMS.

Application:

Identification of the cause of metabolic acidosis with increased anion gap in an infant or child if an organic acidaemia is suspected.

Diagnosis of certain genetic diseases in which abnormal organic acids occur without metabolic acidosis.

Interpretation:

In some diseases the abnormality is present only intermittently (eg, during metabolic acidosis).

The nature and relative amount of organic acids detected usually allow the complete identification of the type of organic acidaemia present and at least narrow it down to a relatively small group.

Abnormal organic acids are often seen in non-genetic lactic acidosis and ketoacidosis and careful interpretation is required.

In some rare disorders (eg, type I tyrosinaemia, Canavan disease) abnormal organic acids are present in the absence of metabolic acidosis - consult pathologist.

Reference:

Chalmers RA. In: Holton BJ ed. The Inherited Metabolic Diseases. 2nd ed. 1994. Churchill Livingstone.