Test Overview
Test Methodology

Mass Spectrometry

Test Usage

Diagnosis of Trimethylaminuria.

Reference Range *

Interpretive report provided.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Details
Soft Order Code
  • Trimethylamine (TMA) and TMA N-oxide (TMAO) (Quantitative)
Reference Laboratory
Mayo Wild 246 (ZW246, L6949) (Children's Hospital Colorado)
Special Testing
Specimen Requirements

Send 1 - 5 mL of morning void urine, collected when the patient is eating an unrestricted diet and odor is present. Please note that very dilute urine cannot be accurately tested. Acidification of the urine to pH = 4 is preferred, although not required. Freeze the urine immediately after collection in a durable, tightly-sealed specimen tube and ship frozen on dry ice; do not ship in brittle polystyrene urine collection cups.
One specimen collected as described above is acceptable, however, the following choline load protocol is strongly recommended: [list order = Y]
Collect a pre-choline load urine specimen as described above. The urine specimen should be acidified to pH = 4 (if possible), and should be frozen immediately in a durable, tightly-sealed specimen tube and stored frozen until shipment.
A second urine specimen should then be collected post-choline load, about 12 hours after the patient has ingested choline bitartrate with a glass of orange juice or water [5000 mg of choline bitartrate for patients >12 years and weighing >54 kg (120 lbs); 2500 mg for patients aged >12 years and weighing < or = 54 kg (120 lbs)]. Ingestion of a choline load may cause stomach upset in some patients and is not recommended for patients aged <12 years. Choline bitrate is available from Douglas Laboratories, provided in 500 mg capsules.
Immediately after each collection, each specimen should be acidified to pH = 4 (if possible) and should be frozen in a durable, tightly-sealed specimen tube. Please clearly label each of the specimens "pre-choline" or "post-choline" and store both specimens frozen until shipment. Both the pre-choline and post-choline specimens should be shipped together, frozen on dry ice.

Normal Volume
5 mL aliquot from random urine
Minimum Volume
1 mL aliquot from random urine
Additional Information

Trimethylaminuria is a presumably genetic defect in the enzymatic conversion of trimethylamine (odor of stale fish) to trimethylamine-N-oxide (non-odiferous). Diagnosis is made by detection of excess trimethylamine in urine. Available treatments include dietary restrictions of choline and foods containing trimethylamine inhibitors. Test sent to Mayo Medical Laboratories; performed by Children's Hospital Colorado.

CPT Code
83789, 82570