Can hair be affected by cross-reacting substances such as over-the-counter medications in drug testing?
Enzyme-immunoassay antibodies (EIA), similar to those usedto test urine for drugs, are used for the initial drug screening in hair; therefore the potential for substances such as over-the-counter medications to cause a false positive screening result does exist. To eliminate the possibility of reporting a false-positive result due to cross-reactivity, our laboratory performs Gas Chromatography Mass Spectrometry (GC/MS) for all specimens that screen positive.
