What do the percentages mean in methamphetamine “d” and “l” isomer test results?
In order to help determine whether a methamphetamine positive may be due to an illicit source, it is helpful to determine the percentage of “d” isomer. For example, following an individual’s use of Vick’s Vapor Inhaler, the expected result would be 100% “l” methamphetamine. However, there is a possibility that trace amounts of “d” isomer may be present in the quantitative analysis. Laboratory guidelines have been established to allow for trace presence of the “d” isomer. If the laboratory report indicates more than 80% “l” methamphetamine, the results are consistent with Vick’s Vapor Inhaler use. If the laboratory reports more than 20% “d” methamphetamine present, the result indicates the use of “d” methamphetamine other than the inhaler. Illegally produced methamphetamine and amphetamine may contain mixtures of “d” and “l” isomers. LabCorp recommends use of a medical review officer (MRO) to review all non-negative test results.
