Drug proficiency test false positives: a lack of critical thought

Drug proficiency tests were surveyed in an attempt to determine the cause of false positive results. The results of seventeen drug proficiency tests and surveys provided by Collaborative Testing Services (CTS) over an eight-year period were evaluated. A total of 63 errors were reported for an average rate of 2.8%. Fifty-six of the 63 respondents responsible for errors had used GC-MS, IR or a combination of the two in their analytical scheme. No errors were reported by respondents using two microcrystalline tests. Further evaluation of the analytical schemes of those responsible for the errors demonstrated that it was not the methodology that resulted in the errors, but rather the lack of critical thought on the part of the analyst.