The laboratory has historically been demonstrated to be more effective and economical when centralized. One benefit of a centralized laboratory is that the handling and analysis of each specimen is identical. This high-volume production environment reduces the potential for errors through the efficient processing of thousands of specimens daily under strict controls and supervision. Decentralization of the analytical process to the point of collection, without proper standardization of procedures, instruments (point-of-collection devices), aliquoting methods, or translation and transcription methods, lends itself to a lack of consistency and control from location to location. Experience has shown that employers using multiple locations, especially large employers with hundreds or thousands of locations, are concerned about the lack of uniformity in the testing process from collection site to collection site.
In the laboratory-centric model of DOA testing, the testing process of negative and positive results is essentially indiscernible by all except those deeply engaged within the confirmation laboratory. Although the screening and confirmation laboratory are under one roof in a centralized laboratory facility, they are actually distinct in their objectives. The object of the screening laboratory is to identify which samples are negative (i.e., contain no drugs). The object of the confirmation laboratory is to identify which samples are positive (i.e., contain drugs). Nearly all laboratories utilize immunoassay testing, an inexpensive yet highly sensitive screening method capable of detecting nanogram quantities of drug analytes in a milliliter of urine. This highly sensitive method of screening, combined with automation and robotics in the laboratory, cost-effectively eliminates more than 93% of all specimens from further testing in normal workplace demographics. Criminal justice testing, with its inherently higher positive rates, would require more screened samples to go on for further testing, whereas certain workplace demographics (e.g., airline employees, federal workers, and so on, with inherently low positive rates) have seen negative screening rates as high as 99%. The importance of the negative screening rate cannot be overemphasized, because once a specimen screens negative it is discarded. It cannot be used again or retested, and has no further value to the laboratory or customer
(employer). Only the screened positive samples are transferred to the confirmation laboratory for further testing. In the past 20 yr, data compiled on workplace drug-testing statistics indicated that the positive rates were falling annually, from a high of 25% in 1987, the first year such data were published, to about 7% in the past year. Improved awareness and increased use of drug education and testing methods may cause further declines in the positive rate over the coming years. As positive rates drop even further, it will no longer make sense economically or logistically to send 95% of samples to a laboratory only to find out that they were negative to begin with. Unbundling negative from positive samples at the point of collection and handling the processes separately was of significant importance to the marketplace.
The decentralization of laboratory services to the point of collection is made possible by the improved sensitivity and specificity of drug detection by lateral-flow DOA (LFDOA) testing devices. In the early 1990s, the sensitivity rate of LFDOA testing devices was approx 93% of the thresholds required for standardized workplace drug testing (then referred to as the National Institute of Drug Abuse [NIDA] cut-off levels). Tracking the progress of monoclonal techniques and antibody-antigen sensitivity and specificity demonstrated that overall, DOA sensitivity levels would improve at the rate of approx 1% annually. Beginning in 1993, it was expected that sensitivity rates for LFDOA devices would approach the sensitivity rate of laboratory-based immunoassays (then at 99%) by 1999. Once the sensitivity rate of LFDOA was equal to or better than laboratory-based immunoassays, one could easily argue for not sending negative samples to the laboratory.
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