The sample required is a single random urine specimen while the patient is on a normal, unrestricted diet. Please provide the patient with pages 2 and 4 of the TMA document along with one (1) sterile urine container and a biohazard bag. The sample needs to be frozen as soon as possible after collection and sent to the Pathology Queensland Central Laboratory in Brisbane, along with the patient checklist. Creatinine, trimethylamine and trimethylamine-N-oxide concentrations in the sample will be determined.
This initial testing procedure is likely to identify patients who have primary genetic trimethylaminuria (i.e. two disease-causing mutations in the FMO3 gene). It may also identify some patients with secondary trimethylaminuria.
PROCEDURE B - FOLLOW-UP TESTING
If the results of the initial testing are normal but clinical suspicion of trimethylaminuria remains high, a dietary loading test may be performed for further evaluation. This may be necessary if the patient has a milder or more intermittent form of trimethylaminuria, or is a carrier for primary trimethylaminuria (i.e. one disease-causing mutation in the FMO3 gene). Please note that if the patient is pregnant, it is recommended that follow-up testing is deferred until after the baby is born.
The following is the Pathology Queensland recommended loading test procedure:
1. Administer a diet low in choline and trimethylamine for 3 days.
2. At the end of the 3 days and just before the evening meal, collect a random urine sample and freeze.
3. At the time the patient would normally eat in the evening (around 6 – 8pm) give a meal containing marine fish (NOT freshwater fish). The amount of fish given should be 300g for adults, or 5g/kg for patients under 50kg. It should be noted that a small number of people are allergic to fish.
4. Collect the first urine sample passed the following morning and freeze.
5. Collect another urine sample at around midday and freeze.
Please provide the patient with pages 2, 3 and 4 of the TMA document along with three (3) sterile urine containers and a biohazard bag. All samples should be sent together to the Pathology Queensland Central Laboratory in Brisbane, along with the patient checklist. Creatinine, trimethylamine and trimethylamine-N-oxide concentrations will be determined in all samples.
The loading test procedure is likely to identify patients with mild or intermittent forms of trimethylaminuria, or carriers for primary trimethylaminuria. If the patient’s condition is intermittent, the loading test is best done at a time when the odour is more prominent.