Discussion: caveats in testing for drugs of abuse

Four mass screening techniques for drugs of abuse (TLC, RIA, EMIT, and FPI) have been described. For small-scale screening, TLC is the most cost-effective. Although it cannot achieve the sensitivity of the other three immunologically based techniques, TLC is sufficient for many purposes. All screening techniques are subject to interferences that can generate false-negatives or false-positives. These results must be taken into account in analysis of the research data. In applying technology in new areas of research, one has to be aware of the basis and limits of that technology. Testing of drugs of abuse in urine is a well-known technology in which most of the problems have been discovered. This technology is less proven for other media, such as hair, saliva, or meconium, leaving potential pitfalls for the unwary researcher.