did you get any response to this question? i am seeking the same information?
Didn't notice this post. Sorry we missed you. The post you replied to is very old. It's well over four years old. There are some more recent accounts of people getting false positives while using valerian root, st johns wort and kava kava as well as some steroidal anti-inflammatory RX drugs. Will try to help you if I can. God bless.