Evaluating screening test protocols to assess methamphetamine contamination in buildings

In some states, the discovery of a building where methamphetamine (meth) has been manufactured (cooked) or used triggers a regulatory requirement to perform meth sampling, which may be costly due to the number of mandated samples. Less costly screening tests are sometimes conducted using fewer samples that are collected in a biased manner to minimize false negative (FN) results, but their accuracy has not been previously determined. In this study, results from two screening protocols used in Colorado were compared to results from the more comprehensive Colorado regulatory protocol. Using the results of the comprehensive protocol as the benchmark, the screening tests were evaluated for the frequency of false positive (FP) and FN results. The principal concern is a FN result, where a screening test indicates a lack of significant contamination and a comprehensive test indicates contamination above regulatory standards. Few FNs were found, and the degree of contamination above regulatory standards in those few cases was small. A threshold can be established for specific screening tests that trigger additional testing. Logistic regression was used to determine the FN rates for both screening tests with respect to a range of threshold concentrations. The analysis indicates that both screening tests had FN rates approaching 0% at a threshold lower than the regulatory standard. Location-specific and whole-house average meth concentrations were calculated to identify hotspots where meth concentrations tend to be higher than on other surfaces. Hotspots include kitchen fan/stove areas, bathroom exhaust fans, and furnace/ductwork systems, where concentrations exceed average house concentrations by 41-, 47-, and 17-fold, respectively. These data and analyses demonstrate that simplified and less costly sampling protocols can be a valid screening approach. A sampling protocol for meth screening tests is provided and includes aliquots from the hotspots with the highest concentrations.