K,
A reading to two decimal places is "ultra sensitive", so with a <0.04, you are already getting one.
I had this same discussion with my GP Thursday, as the insurance company is forcing a change in labs again. The new lab offers two tests:
1) "Screening" which offers results to one decimal place, with which you would be a <0.1, or "undetectable".
2) "Post Surgery" which offers results to two decimal paces, but they do not specify the lower detection limit. Your <0.04 would be "undetectable" in that scheme.
We called the lab, and they said that they process "ultra-sensitive" requests as "Post surgery".
My uro uses Bostwick, but will not do ultra-sensitive. He considers it unneeded anxiety.