Prescription drug abuse has reached crisis levels: overdoses and deaths from opioid analgesics have more than quadrupled in the U.S. since 1999. At the same time, a great deal of human pain and suffering remains inadequately treated. In fact, according to the Institute of Medicine, at least 100 million Americans suffer from chronic pain, creating an imperative to better prevent and manage persistent pain[i].
One of the greatest challenges to present day treatment of chronic pain is identifying which patients may be potentially at risk prior to the initiation of opiod therapy, and identifying patients in whom these problems develop during therapy. In order to do this, patients in pain management programs are often assessed before treatment and monitored while they are receiving treatment[ii].
Urine drug testing (UDT) is often a part of this monitoring strategy; it is most often used as part of a multifaceted intervention that includes other components such as patient contracts. Results of a UDT provide confirmation of the agreed-upon treatment plan (adherence/compliance). They can diagnose relapse or drug misuse as early as possible, and they also can be used to advocate for the patient with third-party interests. The purpose of UDT should be explained to the patient at the initial evaluation. UDT can also enhance the relationship between healthcare professionals and patients by providing documentation of adherence to mutually agreed-upon treatment plans[iii].
In the pain management setting, the presence of an illicit or unprescribed drug does not necessarily negate the legitimacy of the patient’s pain complaints, but it may suggest a concurrent disorder such as drug abuse or addiction. The patient must be willing to accept assessment and treatment of both disorders to receive adequate outcomes in either. Thus, the diagnosis of a concurrent addictive disorder, when it exists, does nothing to negate a legitimate pain disorder; rather, it complicates it.[iv]
Urine is the preferred specimen for drug abuse testing primarily because it is non-invasive. Drug levels in blood only reflect the presence of a drug at a given point in time, and levels may be high enough to be detected only for a relatively short period of time. Urine specimens may contain detectable levels of drug over an extended period , often as much as 2-4 days, and at much higher concentrations than in blood[v]. (See Table 1)[vi]. Urine may also contain higher levels of drug metabolites than blood, providing further evidence of drug use.
The healthcare professional must know the drugs for which to test, appropriate methods to use, and the expected use of the results obtained. Immunoassay drug screens are most commonly used, as some of these can be readily performed in physician office settings. They are designed to classify substances as either present or absent and are generally highly sensitive. However, in pain management, specific drug identification using more sophisticated identification tests is needed.
Basically, an effective drug screening program will involve a two-step process: the Initial (immunoassay) and then confirmatory (gas chromatography-mass spectrometry [GC-MS]) testing. These are the methods most commonly utilized to test for drugs. Using a combination of both tests allows a high level of sensitivity and specificity, meaning there is an extremely low chance for false positives or false negatives.
The immunoassay (EMIT, ELISA, and RIA are the most common) is performed first and used as a screening method. If the immunoassay is negative, no further action is required, and the results are reported as negative. A “dipstick” drug testing method which provides screening test capabilities to field investigators has been developed as well. The latter is gaining wide use in physician offices due to its simplicity of design and utilization.
If the sample is positive, an additional confirmatory GC-MS analysis is performed on a separate portion of the biological sample. The more specific GC/MS is used as a confirmatory test to identify individual drug substances or metabolites and quantify the amount of the substance. Confirmatory tests, such as GC-MS should be utilized prior to reporting positive drug test results. False positive samples from the screening test will almost always be negative on the confirmation test. Samples testing positive during both screening and confirmation tests are reported as positive to the entity that ordered the test.[vii]
Healthcare professionals also must understand the basic metabolism of commonly prescribed drugs, especially opioids, so they will be able to explain a UDT result that is positive for the prescribed medication and/or its metabolite(s).
Dealing With Unexpected Urine Toxicology Results
UDT in clinical practice must be used to monitor and improve patient care. Unfortunately, these test results may come back unexpectedly negative for a prescribed drug or positive for an unprescribed one. The first step in interpreting these results is to contact the lab to ensure that no clerical errors have been made. If unexpected results are confirmed, there must be a process in place that should include discussing the unexpected result with the patient.
UDT is an effective tool in the assessment and ongoing management of patients who will be, or are being, treated for chronic pain with controlled substances. Most importantly, a healthcare professional should have a relationship of mutual honesty and trust with the patient when using UDT in the clinical practice, as well as maintain open communication with the testing laboratory. The use of UDT should be consensual; it is designed to improve patient care and to assist the healthcare professional to advocate on the patient’s behalf[viii].
Windows of Detection in Urine Drug Testing
|Drug||Approximate Retention Time|
|Barbiturates||Short acting (eg, secobarbital): 24 hours|
Long acting (eg, phenobarbital): 2-3 weeks
|Benzodiazepines||3 days, if therapeutic dose is ingested|
Up to 4-6 weeks after extended dosage (ie, 1 or more years)
|Methadone||Approximately 3 days|
|Cannabinoids||Moderate smoker (4 times/week): 5 days|
Heavy smoker (smoking daily): 10 days
Retention time for chronic smokers may be 20-28 days
|Phencyclidine||Approximately 8 days|
Chronic users: up to 30 days
(mean value = 14 days)
Note: Interpretation of retention time must take into account variability of urine specimens, drug metabolism and half-life, patient’s physical condition, fluid intake, and method and frequency of ingestion. These are general guidelines only.
Originally Published in June 2016 B issue of AAFP- PT POL Insight