The eScreen System

In view of the deficiencies associated with the conventional POCT and the perception that a digital drug test could be created, a system known as eScreen was developed. eScreen combines the benefits of point-of-collection specimen collection with recent advances in information technologies to create an instrumented POCT system. eScreen monitored the progress of LFDOA development closely. LFDOA clearly led the market as the analytical method of choice.

Easy-to-use, low-cost, highly sensitive lateral-flow test strips could do everything that the lab-based immunoassay could do. eScreen did not compete in the manufacturing of LFDOA devices, but realized that commoditization would likely develop as tests got better and cheaper. eScreen uses the current Federal drug testing standards as a starting point, extracts the immunoassay screening procedure from the centralized laboratory, and shifts it to the point of collection. It keeps in place many of the safeguards already built into the laboratory-centric model of testing, including the collection procedure and confirmation testing. This means that the chain of custody, collection procedures, specimen transportation, and confirmation processes were virtually unaffected. eScreen realized that what was desperately needed for the workplace was a method for implementing a sound POCT program that could effectively compete with the laboratory model for testing. eScreen designed a POCT method to wrap around the LFDOA test strip to closely mimic the laboratory model, with screening performed at the point of collection, and with the goal of eliminating the eight critical barriers to POCT (Table 1).

With the sensitivity and precision of the LFDOA test strips rapidly approaching laboratory-based immunoassay levels (21-24), the next issue was to remove the subjective interpretation in POCT. eScreen knew that in order to remove the human subjectivity of interpretation, two essential elements of the LFDOA test had to change. First, it could not be readable by a human. This meant that the test result would have to be invisible to the naked eye, or be coded, or otherwise obscured from human interpretation. Secondly, it had to be decoded by an instrumented device, or reader. The transition from human vision to machine vision was inevitable.

By 1997, machine-vision systems were appearing in a variety of applications. Eyeball-type video cameras had dropped in price to unimaginable levels, and were appearing on every desktop, even though there were few applications for them, and less than adequate bandwidth to transmit quality video. Low-cost digital video charge-coupled device (CCD) processors were migrating into digital cameras, plant automation, and a myriad of machine-vision applications in medicine, logistics, inspection, quality systems, and robotics.

The task of removing human vision and interpretation at first seemed a fairly simple one. The practical application was much more difficult than first imagined. Strip characteristics, lighting, and lot-to-lot variability in strip manufacturing posed enormous obstacles. Precision application of target zones was necessary to allow the machine vision to focus on the areas of interest. Sharp demarcation between bars and spaces, an essential element in analog barcode readers, could not be achieved with lateral-flow devices. Background noise, in the form of conjugate streaking and carry-forward through the nitrocellulose membrane, had to be subtracted out using digital imaging, proprietary mathe-

Table 1

Eight Critical Barriers to Manual Point-of-Collection Tests (POCT)

Barriers

Proposed Solution

Sensitivity The sensitivity of lateral-flow drugs-of-abuse testing must meet or exceed lab-based immunoassay sensitivity levels.

Aliquoting Specimen must be aliquotted under tamper-evident seal.

Subjective Machine-vision system or instrumented interpretation reader interpretation is required to interpret test result from lateral-flow device.

(translation)

Bias No human operator or opportunity to influence the test result.

Confidentiality Result is unknown to donor, collector, or collection-site personnel.

Transcription No result data entry or manual result reporting from collection-site personnel to employer.

Consistency Each site uses identical operating procedure and standardized conditions for testing.

Endorsement Adoption of the instrumented POCT system by large, national employers, or federal agencies, to drive standardization at local collection sites.

matical algorithms, and software logic. Solutions to these issues were built into the components of the eScreen system.

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