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From: Dr. Steve
Password: orange
Date: 20 Mar 2008
Time: 07:54:54 -0800
Remote Name: 74.10.7.238
I have been doing MRO work for so long, that I can tell you that a great many substances can cause a great many of false positives in immunoassay screenings. This is why all specimens that screen positive should be sent to the lab for GC/MS confirmation testing. I have stopped maintaining a list of what drugs can cause false positives for "something" for exactly that reason. Of note I have found an article that discusses such a case at this link: http://www3.interscience.wiley.com/cgi-bin/abstract/73001404/ABSTRACT?CRETRY=1&SRETRY=0.
There are a few other references I also saw that discuss this issue as well.
Screening tests are just that. A rapid, usually inexpensive way to screen out the vast majority of negatives. However when looking for a drug they are very sensitive, but not that specific, and as such pick up a variety of false positives.