CPT Code:

83789

Availability:

Monday - Friday, 0800 - 1700.

Turnaround Time:

Three weeks.

Minimum Volume:

1.0 mL.

Specimen Handling:

Random urine, collected when the patient is eating an unrestricted diet and odor is present. Acidification of the urine (e.g. adding a small amount of hydrochloric acid to pH < 4) is preferred, although not necessary. Freeze the urine immediately in a durable, tightly-sealed specimen tube and ship frozen on dry ice. See additional information below.

Interpretive Reference Range:

     Normal ratio TMA/TMAO = 0.0025 - 0.055 ( > 85% TMAO )
     Affected ratio TMA/TMAO > 0.2 ( < 20% TMAO ).

Use:

Diagnosis of trimethylaminuria.

Methodology:

Stable isotope dilution tandem mass spectrometry (MS/MS).

Additional Information:

Although not absolutely necessary, this laboratory strongly recommends the following choline load protocol:

     A pre-choline load urine specimen is collected as described above under "Specimen Handling" (the pre-choline load urine specimen should be acidified, if possible, and 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* [5 gm (5000 mg) for patients > 12 years , and 2.5 gm (2500 mg) for patients > 6 years] in one glass of orange juice. The post-choline load urine specimen should be acidified, if possible, and frozen immediately in a durable, tightly-sealed specimen tube and stored frozen until shipment. Please clearly label each of the specimens “pre-choline load” or “post-choline load.” Ship the frozen specimens on dry ice.

* For patients in North America, this laboratory recommends the use of Choline Bitartrate from Douglas Laboratories, provided in 500 mg capsules (10 capsules = 5000 mg). Although not sold directly by Douglas Laboraties, this product is readily available at an affordable price in many U.S. stores or from many internet retailers (link opens in a new window).