<<Disclaimer: Verify this information before applying it to your situation.>> Many thanks to those who responded to my question about false positive blood tests. Most agreed that, indeed, there can be false positives, and many respondents gave anectodal evidence. The response that follows was the most clearly stated. Again, thanks to those who responded. "Yes, there are false positive lab tests as well as false negative ones. In fact, these are the two types of errors that most labs work very had to minimize...it's nearly impossible to get rid of them altogether. A false positive occurs when the lab test comes back positive (e.g., elevated levels of IGA/IGG) and the gastroenterologist then orders a biopsy (the definitive test for celiac sprue) and it comes back negative; that is, clean or ok. In such a case the positive antigen test was due to some other factor other than sprue.. and these can be many. Likewise, a false negative occurs when the initial test comes back negative but a later test reveals the true existence of the suspected disease. This is why medical science/art rarely relies on a single finding to draw a conclusion...or...for that matter, on a single opinion."