CLINICAL ISSUES :: DRUG TESTING AND MONITORING


testing for criminal trial or motor vehicle accident investigation.


Specimen types for drug testing The U.S. Department of Health and Human Services (DHHS) set guidelines for drug testing. Laboratories performing drug testing include a centralized clinical chemistry laboratory, point-of-care (POC) facilities, physician’s office labs, and emergency centers. Urine is the most used sample type for drug testing. The other possible matrices are hair, blood, sweat, and oral fluid (saliva). Every specimen type has its pros and cons as shown in Table 1.13


Figure 3. Factors influencing drug addiction.


testing to monitor if a patient is taking the right amount of a prescribed opioid medication. Nonclinical reasons include the following: • Employment: Employers may request drug testing before recruitment or on-the-job. • Sports: Athletes may be required to get tested for drugs before and/or after a competition. • Legal or forensic purposes: Court cases may order drug


Specimen Type


Urine Pros


• Easy to collect • Available in sufficient quantity • Higher concentration of parent drug compared to in blood


•Well-researched testing techniques


• Availability of POC tests Oral Fluid


• Easy to collect • Reduced risk of adulteration • Parent drug (not the metabo- lite) can be detected


• Availability of POC tests Hair screening followed by a confirmatory test.15


Drug of abuse testing Drug abuse testing gener- ally follows two steps: initial Initial drug


• Easy to adulterate or substitute • Window of detection 48–72 hours on an average • May require observed collection • Some individuals experience “shy bladder” syndrome and cannot produce a specimen


• Cannot measure frequency of drug use, nor can it indicate severity of addiction


• Detects recent drug use (up to 48 hours)


• Long detection window (up to 90 days)


• May be able to detect changes in drug use over time (from 7–10 days)


Blood


• Generally, detects recent use • Established laboratory test method


Sweat


• Detects recent use (fewer than 24 hours with a sweat swipe) or allows for cumulative testing with the sweat patch (worn for up to 7–14 days)


• Easy, noninvasive method • Difficult to adulterate


• Limited specimen volume • Salivation reduced by stimulant used • Possibility of contamination with residual drug in mouth that does not correlate with blood concentrations


• Cannot detect drug use beyond 48 hours • Cannot measure frequency of drug use, nor can it indicate severity of addiction


• Takes approximately 5 to 10 days from the time of drug use for detection


screening is carried out most of the time using an immu- noassay. In the immunoassay method, an antigen (drug) and antibody are made to bind to identify drug analytes. The antibodies are produced to be drug specific. A known amount of antibody is added to a specimen, along with a drug that has been labeled to distinguish it from the drug in a donor’s urine specimen. The labeled drug and the unla- beled drug (if any) compete for the antibody to form an antigen-antibody complex. The ratio of the labeled and unlabeled drug bound to the antibody allows the measurement of the amount of drug in the donor’s urine specimen. Advantages of immunoassays are their ease of use, fast turnaround times, lower costs, and results may be qualitative or semi-qual- itative. Immunoassays may be of different types: • Enzyme


Cons immunoassays


• Costly and time consuming to prepare specimen for testing • Usually a longer turnaround time for results • Not applicable if the donor has shaved or is void of head/ body hair


• Narrow detection window of 2-12 hours • Invasive specimen collection (venipuncture) that requires phlebotomist


• Rarely conducted in POC setting


• Few facilities & limited expertise for testing • Risk of accidental or deliberate removal of the sweat patch collection device


• Unknown effects of variable sweat excretion among individuals


• Only a single sweat collection patch available so multiple analyses cannot be done if needed (i.e., more than one positive initial test)


Table 1. Drug testing specimen types and their pros and cons. 18 DECEMBER 2022 MLO-ONLINE.COM


(EIA) • Cloned enzyme donor immunoassay (CEDIA) • Fluorescence polarization immunoassay (FPIA) • Kinetic interaction of mic- roparticles in solution (KIMS) • Microplate enzyme-linked immunosorbent assay (ELISA) Specimens that are positive


• Requires two visits, one for patch placement and one for patch removal


by immunoassay need to be confirmed using a different analytical method. A confir- matory test method needs to identify and quantify the drug or drug metabolite. The


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