Urine Drug Testing Update

EDUCATIONAL COMMENTARY ? URINE DRUG TESTING UPDATE

Educational commentary is provided through our affiliation with the American Society for Clinical Pathology (ASCP). To obtain FREE CME/CMLE credits click on Earn CE Credits under Continuing Education on the left side of the screen.

Learning Outcomes Upon completion of this exercise, the participant should be able to:

compare and discuss clinical and workplace drug testing. list the drugs and the approximate window of detection of each when the testing follows

guidelines for federally regulated samples. interpret positive and specimen validity testing results for (federally) regulated drug testing

specimens.

Laboratories may be involved with testing biologic samples for the presence of drugs for the diagnosis and monitoring of the patient who has overdosed (clinical testing) and for workplace drug testing (forensic testing). While the purposes for the testing differ, the same methods are often used for both because of the availability and ease of use of immunoassays on automated instruments.

In the emergency department physicians initially treat the signs and symptoms of the patient who has overdosed and rely on the laboratory drug testing results to confirm the diagnosis and to possibly monitor treatment. The National Academy of Clinical Biochemistry (NACB) practice guidelines for the use of laboratory tests to support poisoned patients recommend that the clinical laboratory provide two tiers of drug testing: a first tier of qualitative and quantitative tests available on a stat basis to evaluate acute toxicity for specific toxins (Table 1) for which an antidote or specific therapy is available and a second tier (turnaround time of 24 hours or less) of more comprehensive testing for patients with continuing medical problems from exposure to other drugs and chemicals. Although these guidelines should be revised in the near future, they are still relevant, and few changes are anticipated. One probable revision is the replacement of barbiturates in a qualitative initial screen with benzodiazepines because benzodiazepines have replaced barbiturates as the class of sedative hypnotics most often used and abused. Current immunoassays lack the sensitivity and specificity to detect all benzodiazepines.

American Proficiency Institute ? 2011 1st Test Event

EDUCATIONAL COMMENTARY ? URINE DRUG TESTING UPDATE (cont.) TABLE 1. Recommended Stat Quantitative Serum and Qualitative Urine Assays Required to Support an Emergency Department. Quantitative Serum Assays Acetaminophen, lithium, salicylate, theophylline, co-oximetry (O2 saturation, carboxyhemoglobin, and methemoglobin), valproic acid, carbamazepine, phenobarbital (if urine barbiturates are positive), digoxin, iron, transferrin (or UIBC assay), ethyl alcohol, methyl alcohol, ethylene glycol Qualitative Urine Assays Cocaine, opiates, barbiturates, tricyclic antidepressants, amphetamines,* propoxyphene,* phencyclidine*

*The need for these assays may be based on the prevalence of drug use in the region. SOURCE: Wu AHB, McKay C, Broussard LA, et al. National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines: recommendations for the use of laboratory tests to support poisoned patients who present to the emergency department. Clin Chem. 2003;49(3):357-379.

Workplace Drug Testing On October 1, 2010, several changes to the 1988 Mandatory Guidelines for Federal Workplace Drug Testing Programs were implemented. The guidelines and subsequent revisions mandate scientific and technical procedures for the drug testing process including: collection; transportation of specimens; testing procedures incorporating quality control, method evaluation, and results reporting; and standards for laboratory accreditation by the National Laboratory Certification Program (NLCP). Although privatesector industries are not required to follow the guidelines developed for the Federal program, many choose to do so.

Urine is the specimen of choice for both clinical and workplace drug testing with certain exceptions (i.e., ethanol testing under Department of Transportation guidelines in which breath, blood, or saliva matrices are acceptable; Table 1 for clinical samples). Urine offers the advantages of noninvasive collection and a relatively easy, cost-effective, proven technology versus the disadvantages of a short window of detection (Table 2) and lack of correlation between concentration and impairment. Federal guidelines mandate a controlled collection and use of standardized Custody and Control forms as the specimen requisition, chain of custody, and official report form.

A laboratory may only test for certain drugs at specified cutoff levels for Federal workplace drug testing (Table 2). Testing for other drugs (e.g., barbiturates, benzodiazepines, propoxyphene, methaqualone) and at other cutoff concentrations may occur for nonregulated and clinical samples. This discussion will be limited to the drugs included in the Federal workplace drug testing program. Regulated testing mandates initial screening by an immunoassay method and subsequent confirmation of all screeningpositive samples by gas chromatography/mass spectrometry (GC/MS) or other approved methodologies

American Proficiency Institute ? 2011 1st Test Event

EDUCATIONAL COMMENTARY ? URINE DRUG TESTING UPDATE (cont.) such as liquid chromatography with tandem mass spectrometry (LC/MS/MS). Immunoassays use an antibody whose reaction with the drugs and/or metabolites is monitored using some type of measurable label such as an enzyme or chemiluminescent compound. Clinical testing may use any combination of methods available and does not require confirmation by a second method.

TABLE 2. Cutoff Concentrations and Approximate Detection Period for Federal Workplace Drug Testing Programs.

Drug/Class

Screening, Confirmation,

Detection Period,

ng/mL

ng/mL

days

Amphetamines

500*

2-3

Amphetamine

250*

Methamphetamine

250* (must have amphetamine

at >100 ng/mL*)

MDMA*

500*

250*

2-3

MDA*

250*

MDEA*

250*

Marijuana metabolites 50

15 (THCA)

5-7 (single use)

(cannabinoids)

Cocaine metabolite 150*

100*

2-3 (up to 16 for chronic use)

(benzoylecgonine)

Opiates

2000

3-4

Codeine

2000

Morphine

2000

6-Acetyl-morphine* 10*

10

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