Urine Orotic Acid

Clinical Utility

This selected ion monitoring gas chromatography mass spectrometry (SIM-GCMS) quantitative method for measuring orotic acid, which is intermediary metabolite of the de-novo pryrimidine synthesis pathway. Patients with hyperammonemia, caused by deficiencies in various urea cycle enzymes show elevation in the urinary excretion of orotic acid. This test is recommended in the differential diagnosis of hyperammonemia, in combination with the MSMS analysis of blood for basic amino acids.

Specimen type:

The most appropriate sample is material is random urine collected during during the hyperammonemic phase (5-20 ml; minimum 2 ml) in a tube and shipped frozen with a coolant pack. An acceptable alternative is a dry urine spot collected on filter paper (Instructions for urine spot collection).

Turn-around time:

Routine: 3-7 days from recipt of sample

Stat: 24-48 hours from receipt of sample

Test Limitations & Interference: None.

Reprot Format:

The result is given in a one-page report that details the patient information, date of sample, date of analysis and a result code that could be one of three:

"NOT REMARKABLE" "QUESTIONABLE" "ABNORMAL"

The values obtained for orotic acid will be provided. Interpretation of questionable or abnormal results will be provided. Recommendation for follow-up samples, or further tests, which are needed for confirmation, will be indicated.