Can Vivitrol cause a false positive in a urine drug test?

Drug test can be very unreliable. There are posts here every day where someone in pain management programs tested falsely negative and normal everyday people test positive for things they did not take. My counselor had it happen a time or two and she said that sometimes the whole batch of tests shipped in were bad and if they kept showing the same illegal narcotics in a group of people, she ran one on herself as a test. If it came back positive (she knew she was clean) she threw the whole batch of tests out. If it was a mail off to a lab test, it can still be read wrong or switched with someone else's test. Blood work can be done to double check the results and probably should be.