URINALYSIS FOR PRESENCE OF DRUGS AND THEIR METABOLITES IN THE CRIMINAL JUSTICE POPULATION: Rapid Screen Testing vs. LC/MS/MS Laboratory Testing
Ronnie J. Blanton
James P. Nelson
Point of Collection (POC) urine testing for drugs of abuse, also called presumptive testing, has become a commonly accepted form of testing in the criminal justice field and in substance use disorder treatment programs as well. The most common reasons for this are cost, convenience and availability of rapid results.
The procedure typically used is as follows:
The test subject deposits a urine sample in a disposable beaker, sometimes observed by a monitor, sometimes without a monitor.
The sample is inspected to determine temperature range, color and smell.
A disposable device (composed of a series of strips of blotter paper coated with stripes of chemically reactive solution which change color when exposed to a specific drug or its metabolites) is dipped in the sample.
After a brief time interval, usually 5 minutes, the appearance of colored stripes indicates a negative result.
If a colored stripe does not appear, the result is presumed to be positive.
If a positive result is obtained, the remaining sample is packaged, and shipped to a contract laboratory for further analysis (confirmation).
The laboratory either confirms the screen result (positive), or not (negative).
If a negative result is obtained, the sample is discarded.
The primary reason for the popularity of these devices in some jurisdictions has been the rapid availability of test results, the relatively low cost of the devices, and their ease of use. However, there are several challenges which make this method problematic.
POC urinary drug screen testing has limited accuracy. It is a screening tool only, and can produce false-positive or false negative results due to testing methodology, quality or freshness of the emulsion used, etc. The cutoff concentration may also be too high in some cases, to be useful. Thus, any screening result must be confirmed by mass spectrometry before actual substance use can be confirmed. Also, a misunderstanding of the underlying science can lead to placing too much faith in the validity of these screening tools.
The Unspoken Assumption
In the simple 8-step procedure outlined in the introduction, the assumption is that any error in screening will be corrected in the lab during confirmation. The overt assumption is that any errors which may occur will be false positives. In other words, if a test subject submits a sample that screens presumptively for a positive result (the subject ingested a drug or drugs), but the person did not in fact ingest the drug, the lab finding will be negative.
What is not common knowledge in both the criminal justice and the therapeutic venues, is that a POC test can and will sometimes return a false-negative.
In the event of a false negative, a person who ingested a drug is assumed to have abstained from drug use due to an error in the screening device. No confirmation lab test is done, the sample is discarded, and the subject is excused.
In the interest of finding out how accurate POC tests really are, the study team performed an independent study of the instruments produced by three different manufacturers over a representative sample of 100 devices from each manufacturer from different lots. After being exposed to samples using the procedure outlined in the introduction of this article, each test was packaged and sent to a certified lab where it was also tested using both gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry.
Gas chromatograph (GC) analysis separates all of the components in a sample and provides a representative spectral output. The technician injects the sample into the injection port of the GC device. The GC instrument vaporizes the sample and then separates and analyzes the various components. Each component ideally produces a specific spectral peak that may be recorded on a paper chart or electronically. The time elapsed between injection and elution is called the "retention time." The retention time can help to differentiate between some compounds. The size of the peaks is proportional to the quantity of the corresponding substances in the specimen analyzed. The peak is measured from the baseline to the tip of the peak.
Liquid Chromatography / Tandem Mass Spectrometry (LC-MS/MS) offers today’s best, and most accurate urine testing lab results available on a commercial basis. It combines the advantages of two complementary techniques; Liquid Chromatography and Tandem Mass Spectrometry techniques. High-performance liquid chromatography fractionates the sample to individual analytes while tandem mass spectrometry quantitates the analytes.
300 presumptive test kits were used. In order to increase the internal reliability of the study, 100 kits from each of three different manufacturers were used.
tested for were:
The sample donors were:
57% Male and 43% Female.
75% of them were Caucasian,
15% were Hispanic,
7% were African American, and
3% declined to answer.
Subjects were selected from a random pool of court ordered testers.
Sample Collection Procedures:
The test subjects deposited a urine sample in a disposable beaker. All subjects were observed by a monitor to insure sample validity.
The samples were then visually inspected for temperature range, appearance and unusual odor, and a specific gravity measurement was taken and recorded in order to help insure that each sample was testable.
The disposable device (composed of a series of strips of blotter paper with chemically reactive emulsion stripes which change color when exposed to the designated drug or its metabolites) was dipped in the sample.
After a brief time interval, usually 5 minutes, the appearance or absence of color change among the stripes indicated a positive or negative result. Relative intensity of the color is irrelevant.
If a colored stripe does not appear, the result is presumed to be positive. If a stripe is evident at all, the sample is presumed to be negative.
For the purposes of this study, all the remaining samples were bottled, and shipped to a contract laboratory for further analysis, and the variance or fidelity with the results indicated by the POC device were recorded.
The laboratory either confirms the screen result (positive), or not (negative).
If the result of both the color stipes on the POC device and the laboratory results were the same, the device was considered accurate. If not the device was deemed to be erroneous and therefore, invalid.
Of 300 samples tested, 41 samples (13.5%) were reported by the POC’s to be presumed positive.
65 samples (21.5%) were actually positive, as reported by the lab to be confirmed positive.
33 samples (17.00%) were presumed to be negative, but were actually positive (false negatives). See Table 3 below.
21 samples (7.00%) were presumed to be positive, but were actually negative (false positives). See Table 2.
10 samples (3.33%) were too dilute to produce an accurate lab result. This generally does not happen without the client devoting considerable effort to force fluids, or “flushing” their urinary system.
2 samples (.67%) were listed as “Other”. The rapid screen reported these to be positive for opiates but the lab found them to be positive for THC.
In total, a 27.4% error rate was found. (See table 1.) This indicates that 27 out of 100 devices (rapid screens) were defective.
How does this information influence the choice of testing options in the criminal justice and clinical therapy venues?
“Drug testing has the potential to build resistance, particularly if a client is falsely accused. It may be better to let a client “get away with one” then risk a false accusation and re-establishment of resistance.”
Paul L. Cary, MS
University of Missouri, Toxicology Lab
Scientifically valid drug screening and testing may be regarded by some as too costly to be useful. For example, it is less expensive to purchase urinary drug test cups, which contain a presumptive screening device, than it is to send a sample to a laboratory for more comprehensive testing. However, the results produced by these devices are often inaccurate and the results are often misinterpreted. Additionally, staff responsible for performing the screening with these devices often misinterpret the results. The difference between a faint line and a bold line is often used to rationalize the amount of the drug which the subject may have ingested, or the amount of time elapsed since the subject ingested the substance. Neither of these “interpretations” are supported by chemistry.
To be completely accurate, proper testing requires additional mass spectrometry-based lab analysis. There is also a cost associated with managing POC urinary testing, which includes quality assessments of test kits, personnel training, proper documentation of results, etc.
POC is a screening tool only, and can produce false-positive or false negative results due to testing methodology, quality or freshness of the emulsion used, etc. POC urinary drug screen testing has limited accuracy. The cutoff concentration may also be too high in some cases, to be useful. Thus, any screening result must be confirmed by mass spectrometry before actual substance use can be confirmed. A misunderstanding of the underlying science can lead to placing too much faith in the validity of these screening tools. Many people do not understand the presumptive nature of these test results and want to make decisions about the test subject’s compliance with the directive to remain abstinent of drugs and alcohol before laboratory confirmation is received.
In this study, the investigators found that the utilization of a POC drug screen test is very limited. The information it provides is not sufficient to be used as bona fide evidence of drug or alcohol use in either a criminal justice setting or a therapeutic setting.
If the treatment program or testing facility is trying to stretch their budget (and who isn’t) the appeal of the POC is obvious. Used in conjunction with a lab to confirm that a positive screen result indeed indicates a positive sample, seems like the ideal budget solution.
However, the major problem with this method is that it only addresses samples that screen as positive for the drugs examined. It does not deal with false negative tests or dilute specimens in any way.
Confirmation testing for presumptive positives seems to be the answer to most arguments that rapid screens are inaccurate. Unfortunately, as shown in this study, the majority of the inaccuracy stems from false negative results which are never sent to a lab. Meaning the rapid screen gave a negative result but the lab returned a positive result. If we are relying solely on a rapid screen to tell us if the client is using drugs, we are doing a disservice to our clients. In a clinical setting early detection of a relapse is critical to therapy.
In probation and parole applications, using a POC is unjust 27.4% of the time. If a client feels they are being falsely accused of using a banned substance it can cause a resistance that is counterproductive. On the other hand, if they are being excused because of a false negative they begin to feel they can continue using without consequence. There is also the problem of the POC showing a positive result for one substance and the lab reporting them positive for a different substance, what would the consequence be?
Clearly, lab-based testing is superior to the use of POC’s. However, a potential problem with moving to all lab based testing is the turnaround time for results. Most labs have a turnaround time of about three days especially for negatives. Positive tests can take a little more time if they are reconfirming the samples, or the requested test takes a longer amount of time to confirm. If you are already sending your presumptive positives to a lab to be confirmed as positive, the amount of time is no more when you send all samples to a lab. Continuous random testing allows for this time frame to be negligible as when testing in both the clinical field and criminal justice field you are looking for a pattern of abuse that you cannot see with a single test.
The authors of this study have tested the accuracy of the most popular presumptive screening devices and have concluded that not only is there a high rate of inaccuracy, but that the total elapsed time from sampling to lab confirmed result is actually made longer by using presumptive screening devices than when other methods are used. Therefore, sending all collected samples directly to the lab without using a POC screening device would be best practice.
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Gentili, Stephano, et.al., A Study on the Reliability of an On-Site Oral Fluid Drug Test in a Recreational Context: 10 pages, 2016. Journal of Analytical Methods in Chemistry. Vol 2016, Article ID 1234581.
Mastrovich, Todd, et. al., Point of Care Testing for Drugs of Abuse in an Urban Emergency Department: Paterson, NJ: St. Joseph’s Research Institute. 2002.
Cary, Paul S., Urine Drug Concentrations: The Scientific Rationale for Eliminating the Use of Drug Test Levels in Drug Court Proceedings: Monograph, National Drug Court Institute, Vol IV., No.1, 2004