Im not sure. I suppose it would have been mission accomplished if the Dr had said you were smelling :) I think it should be ok. As long as they find enough tma or tma-oxide, it should be an ok challenge. Preferably tma-oxide (the non-smelly finished product). you could ask Annie Capua or the yahoo forum or whatever.
Im not sure what the protocol is. I know it involves a choline challenge in the USA and UK, but in Australia I think the tester tells them to eat fish and eggs for a few days or something. Also I think it may normally be a sample from a collected 24 hour amount. But as long as theres enough tma and/or tma-o, preferably if you were smelling :), I would guess it's reliable.
Personally I don't think tma is responsible for anything other than a fishy smell. I think of it more likely to be FMO Body Odor , but TMAU testing is the only show in town. TMA is an FMO3 substrate.
Well done in getting a medical doctor to test you.