Changeable Bar Code Prelude to Digital Drug Testing

When one examines the results at the target zone of a multi-drug lateral-flow testing device, it appears that the series of color lines and spaces are elements of bar coded symbols. Bar codes, a series of bars and spaces, are encoded data elements representing numbers and/or letters that can be decoded with the proper reader and decoder software. The configuration of the lateral-flow device with seven or more color lines and spaces may sometimes be confusing. The names of the drugs are marked on the cassette carrier adjacent to the target zone. If the drug names were removed from the cassette carrier, the interpreter would not know which drugs are being tested and which are the positive results. However, this should not matter because the collector is not privileged to know the test results, and consequently, if the test is presumptively positive, the nature of the drug detected is immaterial to the collector, because only the gas chromatography (GC)-mass spectrometry (MS)

confirmation laboratory can positively identify the drug. Removing the drug names from the cassette means that if all the color lines are present, as is the case with most strips, no drugs are detected in the specimen (i.e., the result is negative). If one or more color lines are absent from the series, the result is presumptively positive. It does not matter which drug is detected, because in every case, the outcome is the same. The specimen must be sent to a confirmation laboratory for further testing. From the bar code prospective, this argument presents a unique opportunity to translate the lines and spaces on the LFDOA test strips into a digital code, or a series of 0s and 1s. Consider the presence of a target line as indicated by a 1 and a space by a 0, then a five-drug test with one control line would be translated by a barcode reader into 10101010101 (six lines and five spaces) when the sample is negative and all six lines appear. If, for example, the THC test in the second position is positive, and fails to produce a color change in the target zone, the outcome would be 10001010101. A cocaine positive test, in the third position, would produce 10100010101, and so on. In fact, any combination other than 10101010101 is an indication that the sample requires confirmation testing. Changing the position of the test target zones from lot to lot or from time to time sufficiently eliminates the possibility of learning the code configurations. Therefore, neither the donor nor the collector knows which drug is presumptively positive.

Drug testing by nature is inherently binary, because the outcome of a drug test for employment purposes is ultimately only positive or negative, pass/fail, qualified/unqualified, and so on, or qualitative in its result. In the information flow of drug testing, there exists a point where the analog processes become digital information. This point is referred to as the analog-to-digital conversion point (ADC). In the laboratory-centric model of drug testing, this point of conversion to digital information exists in the interface between the laboratory and the medical review officer (MRO). Improvements in efficiency of information transmission are realized as the ADC point shifts to the left, because little or no data entry or transcription is required into the drug test record after ADC. Digital conversion in the extreme case occurs when the data-entry process begins in the workplace as digital information.

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