Stefan Steinmeyer Rainer Polzius and Andreas Manns

Summary

The Drager DrugTest® System (Drager Safety) is a competitive, lateral-flow immunoassay for the detection of drugs of abuse in oral fluid. It is a point-of-care system comprised of an oral-fluid sample collector, test cassette, and analyzer, which delivers results read by the instrument for the simultaneous detection of the full National Institute on Drug Abuse (NIDA)-5 panel of drugs in a single oral-fluid sample. Oral-fluid testing has significant advantages over techniques involving blood or urine, such as its noninvasive nature, reduced costs and turnaround time, and reduced risk of sample adulteration; it also allows for accurate drug testing for a full NIDA-5 panel virtually anywhere and a more dignified treatment of test subjectsy. Drager DrugTest is a product platform based on Up-Converting Phosphor Technology (UPT™; Orasure Technologies) and is used by law-enforcement agencies primarily to test operators and passengers of motor vehicles (i.e., roadside drug testing). This report provides an overview of the design of the system, the technology used, and the field studies in which the system has been tested.

1. Introduction

The practice of drug testing is undergoing a technological revolution, which is affecting not only the method, but also the location of testing. For on-site testing, such as along a roadside or in an unsecured location, urine drug

From: Forensic Science and Medicine: Drugs of Abuse: Body Fluid Testing Edited by R. C. Wong and H. Y. Tse © Humana Press Inc., Totowa, NJ

screening performance has been limited by the difficulty of specimen collection when no adequate facilities (e.g., police truck with a bathroom) are available and of correlation of test results with drug impairment and blood drug concentration. Some drugs, particularly cannabis, can remain in urine for several weeks, but the impairing effects last a maximum of only 24 h. Therefore, the presence of drugs in urine can only indicate that the individual has been exposed to drugs, but not that he or she is inevitably under the influence. Also, because of privacy issues and potential alteration of a specimen by donors, the development and assessment of alternative test methods continues to be of interest (1-5).

Recent advances in analytical technology have enabled the detection of drugs and drug metabolites in alternative biological specimens, such as in oral fluids, for the purpose of roadside checks, workplace testing, or the testing of individuals under criminal justice supervision (6). Analyzing samples of oral fluid or sweat are relatively new ways for the detection of drug abuse. Oral-fluid analysis is a particularly promising method for the following reasons: An oral fluid sample can be taken directly on site, safeguarding the privacy of the subject. Oral-fluid sampling is not intrusive and guarantees physical safety. Furthermore, there is very little possibility of sample tampering because the operator can monitor the sampling process.

Oral-fluid testing can reveal the presence of pharmacologically active drugs in an individual at the time of testing. Significant correlation has been found between oral-fluid concentrations of drugs of abuse and behavioral and physiological effects (7). Numerous recent studies have proven that oral fluid meets the requirements for drug-of-abuse screening at the workplace, roadside, or other locations (8-10).

In this chapter, the Drager DrugTest® (Drager Safety) is described. This system is a point-of-collection (POC) rapid immunoassay intended for the collection of oral fluids and qualitative detection of drugs through the use of the DrugTest Analyzer.

2. Design of the System

The Drager DrugTest was developed on the basis of findings relating to drug abuse in road traffic and taking into account the recommendations of the European Roadside Testing Assessment (ROSITA) study (see Chapter 17), in which requirements for roadside-testing equipment were identified (11). The device is capable of simultaneously detecting the following classes of drugs: cannabis, amphetamines, methamphetamines, cocaine, opiates, and phencycli-dine (National Institute on Drug Abuse [NIDA]-5 panel). In Figs. 1 and 2, the main components of the system are shown:

Fig. 1. Drager DrugTest® Kit for oral fluid samples (collection device, test cassette and inserted sample preparation cartridge).

1. DrugTest Kit for oral fluids: the collection device for taking the oral fluid sample and the test cassette for detecting the drugs;

2. DrugTest Analyzer: portable instrument for reading the test cassette and for data management;

3. Accessories: impact printer and keyboard (accessories not illustrated in Figs. 1 and 2: negative and positive controls, transportation case).

The entire process of analysis, from collecting a sample to the display of the measurement results on the analyzer, takes around 15 min. Under observation, the subject collects an oral-fluid sample by gently moving the collection device from side to side in the mouth for about a minute until the sponge is saturated, as shown in Fig. 3. As a result, an average of 330 ± 130 ^L oral fluid is collected, sufficient to allow clinically effective screening and confirmation. The fluid is expressed from the sponge by firm pressing of the collection device into the sample-preparation cartridge (SPC) in the test cassette. The handle can then be removed by counter-clockwise twisting, and a 4-min reaction time is started. The SPC should then be pressed down firmly to start an 8-min development time, when the sample flows up the strip inside the test cassette. The different steps of the process are shown in Fig. 1. After the 8-min development, the cassette can be inserted into the analyzer and a test can be read out

Fig. 2. Drager DrugTest® Analyzer with keyboard and printer.

according to the screen prompts. Once the analysis of the cassette begins, a progress bar will appear on the Drager DrugTest Analyzer display. After 3 min of reading, the analyzer reports the results with either a "+" or "-" on the display screen for each drug (Fig. 4). No interpretation is required. There is a greater than 95% confidence level that a positive result will be attained with drug at 250% of its following detection limits (cut-off concentrations; see Table 1).

During the procedure, the subject and the operator data can be entered optionally with the keypad, a connected keyboard, and/or a barcode scanner. The results are automatically stored under their respective sample number (there is enough memory for up to 2000 sets of data) and can be displayed, printed out, or sent via an infrared (IR) interface to a personal computer. After the specimen has been tested, the collector sponge, which remains in the SPC,

Fig. 3. Collection device before (left) and after (right) completion of the sampling process.

Fig. 4. Measurement results on the analyzer's display.

still contains around 200 ^L of the original oral fluid sample, so that this sample can be transported to a laboratory for confirmation. At the laboratory, the collector is pulled out of the SPC in order to remove the sample from the cassette, and the drug is then extracted from the sponge and analyzed by instrumented devices such as gas chromatography (GC)-mass spectrometry (MS).

Table 1 Screening Cut-Offs

Amphetamine Methamphetamines Cocaine metabolic products Opiates

10 ng/mL 10 ng/mL 5 ng/mL 5 ng/mL 20 ng/mL 10 ng/mL

Cannabinoids Phencyclidine

3. Principle of the Test

The detection method is based on a competitive, lateral-flow immunoassay (see Chapters 3 and 4), which utilizes highly specific antibodies for the different drug classes and detects simultaneously the different drugs from a single oral-fluid sample. Drug or drug metabolites in the oral fluid compete with the immobilized drug derivatives for limited drug-antibody binding sites. The degree of binding, i.e., the number of complexes formed by the antibodies and the target substance, depends on the concentration of the target substance. A more detailed description of immunological detection can be found elsewhere (12).

To allow analysis of the immunological binding reaction, a patented signal technology, known as Up-Converting Phosphor Technology (UPT™, Orasure Technologies), is used. The antibodies are covalently conjugated with spherical, crystalline submicrometer-sized particles(phosphors), which are able to absorb IR light and subsequently emit photons in the visible range. Upon excitation with low-energy long-wave laser radiation (980 nm, IR range) during the reading process within the DrugTest Analyzer, the phosphors convert the light up to a high-energy visible emission spectrum. The emitted light is registered, amplified, and quantified by a detector, allowing a very sensitive detection of approx 10 green-emitting particles (550 nm) and 100 blue-emitting particles (475 nm). This up-converting process is unique in nature in that the optical properties of the phosphors are unaffected by their environment. Therefore, there is no contribution to test background phosphorescence from the sample matrix and assay interferents (13,14).

The intensity of the emitted light is an indication of the drug concentration in the sample; there is an inverse relationship between the drug or drug metabolite concentration present in the sample and the signal strength at the test zone.

Fig. 5. (opposite page) Schematic diagram of a morphine test strip and the reading process if the sample does not contain any drug (above), and if morphine is present in the sample (below).

Sample without drugs

= Morphine

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