Below is a link to an article comparing false negative rates using various methods of testing for mites. I believe the PCR method was first used in studies of Demodex and showed much higher rates than with old methods. The interesting thing is, if you read articles in the psychotherapy literature about delusional parasitosis, the authors uniformly assume the validity of old methods like tape testing. So the false negatives with tape testing turn into false positives for delusional parasitosis. Coming soon: a full article on the etiology and sequelae of false diagnoses of delusional parasitosis.