I'm sorry, I forgot to ask if your mother was taking any over the counter medication before her test?
I think our pain management CL may be able to help you with this.She's very knowledgeable about all of this.
I have heard of tests coming up either "dirty" or not showing what the patient has been prescribed and they can very well be wrong. Did your mother ask to be retested as soon as the test came back? It's what I would do if I were in her situation.
I do hope everything turns out alright for your mother and there was just something wrong with the test.
I highly highly doubt it... meth is a pretty specific combination of chemicals.
If you're talking about methadone, the chances are highly unlikely -- 11% of oral methadone is excreted, unchanged, in the urine. The test is pretty conclusive -- false negatives and positives are usually not found.
If you're talking about methamphetamine, false positives can be caused by a wide variety of Rx and OTC medications, including a Vicks Inhaler and Sudafed. Has your mother been suffering cold symptoms?
See the following link for more information.
http://dig.pharm.uic.edu/faq/2011/Feb/faq1.aspx