Point of Collection Testing (POCT) refers to both non-instrument devices, such as immunoassay strips, cassettes, and cups and also to instrument-facilitated urine screening performed at the location where an employee/applicant provides a urine specimen. The key distinguishing feature of POCT devices is that they provide an “immediate” negative test result when there are no drugs detected in the urine specimen. Non-negative or presumptive positive results are also known immediately, however, the specimen must be sent to a laboratory for confirmation of the POCT finding using liquid or gas chromatography/mass spectrometry analyses to identify and quantify specific drug and drug metabolites. The POCT devices can also perform rudimentary specimen validity testing to indicate if the urine specimen has been adulterated or manipulated.
POCT Quality Standards
Many POCT devices are FDA cleared. POCT devices are available for a variety of drug testing panels and with various cut-off levels used to determine a negative vs. a non-negative or positive result. The POCT devices have considerable variability in both specificity and sensitivity of the assays used. Generally speaking, the more specific the assay, the less sensitivity it has. Each drug or drug metabolite has an individual assay designed to detect the target analyte(s), e.g. cannabinoids, amphetamines or opiates. Today, most POCT immunoassays perform very closely to instrumented immunoassays used for screening in the laboratory. Amphetamines, Opiates, PCP, and benzodiazepines have the greatest cross-reactivity with substances that are not the target analyte on GC/MS confirmation.
Reading of POCT Results
The majority of POCT devices rely on the specimen collector “reading a line” (e.g. on the strip, cassette, or window on the cup) for each drug to determine if it is negative or non-negative. Somewhat counterintuitively, the presence of a line means it is negative, absence of a line means the drug was detected on the assay. Each drug assay also has a “control”, and a line must appear in the control channel demonstrating that the assay is in proper working order. Many of the devices also include assays for common adulterants, such as pH and nitrites. There are a few POCT devices on the market that use machine readers/optical scanners to display the results (e.g. eScreen™); this technology essentially eliminates collector/reader variability and error in “reading’ the lines.
POCT is not allowed for federally mandated drug testing programs (e.g. DOT, DHHS). There are a few states that prohibit its use for workplace drug testing programs, or restrict it to pre-employment testing only (e.g. MN, MD, NV, NY, NC, VT). Most states that permit POCT do require that employers have any POCT positive or presumptive positive result confirmed at a certified or licensed drug testing laboratory before using the POCT result to deny employment or taking any disciplinary or employment action.
Laboratory Confirmation Testing
POCT in the workplace is most commonly used in pre-employment or pre-access drug testing when an immediate negative result is desirable so that the hiring process can proceed or the individual can be put to work immediately. It is also being used by some employers as a preliminary screening tool when post-incident/post-accident/post-injury drug testing is required by the employer’s policy. An immediate negative result allows employers to determine that an employee can return to work after the accident rather than be kept off duty until laboratory results of the test are reported (usually 24-72 hrs.). Many employers who use POCT as a preliminary screening tool in post-accident drug testing send all specimens (not only the POCT presumptive positive specimens) to the laboratory for full analysis. Some employers who use POCT extensively incorporate a quality control measure of sending a percentage (e.g. 10-20%) of the POCT negative specimens to the laboratory for full screening and confirmation analysis, in addition to sending all POCT presumptive positives to the laboratory for screening and confirmation.
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