Drug Testing for Chronic Pain Medications: When the Results Are Wrong
Although drug testing is generally fairly accurate, it is not foolproof. There are times when the results of a drug test may be wrong. This can be a major problem for chronic pain patients whose continued treatment may depend on the accuracy of drug testing.
Drug testing is frequently done on chronic pain patients as part of their Treatment Agreement to assure they are taking their medication as it was prescribed. But from time to time I hear from chronic pain patients who swear they have taken their medication exactly as prescribed and have not taken any other type of narcotic, yet their drug test has shown one of three things:
- Too much of the opioid in their system, which would mean they may be taking more of the medication than was prescribed.
- None (or too little) of the opioid in their system, which would lead the doctor to think they may be selling it.
- Another narcotic substance in their system, which would indicate they were taking either an illegal drug or one that had not been prescribed by the doctor overseeing their pain management.
Why a Drug Test May Be Wrong
Let’s take a look at what might cause inaccurate results on a drug test. There are six possibilities that I am aware of:
The accuracy of drug testing depends a great deal on the quality of the lab doing the testing. Unfortunately, accuracy can vary widely from one lab to another. The number of false positives can range from 4% to 50% depending on the lab. Labs that are certified by NIDA (National Institute of Drug Abuse) or CAP (College of American Pathologists) are usually pretty accurate. Some other labs, however, may use less accurate equipment to reduce expenses.
You may have consumed some food or more likely some medication that caused a false positive. Good labs confirm all positive results on GC/MS, which is able to identify most false positives. Here is a site that lists many of the substances that can cause a false positive on drug tests not confirmed by GC/MS: False Positives
Urine drug screens are set to a particular cutoff level and will only show positive for the drug in question if a specified amount of the drug is in your system. It’s possible that the cutoff level for positive on the test you took was unintentionally set too high. In that case, although you may have had the drug in your system, you may not have had enough of it to show positive on that particular test.
The drug screen was incorrectly administered or the specimen was tainted, switched or tampered with (accidently or intentionally) between collection and processing.
The drug screen was misinterpreted and/or recorded incorrectly.
People metabolize drugs at different rates.
If your systems happens to be one that metabolizes them too quickly or not quickly enough, it could affect the results of your drug test.
One of the reasons your metabolism may be off is due to an opioid-drug interaction.
If you are taking another medication that is metabolized by the same enzyme as the opioid medication, they will compete with each other for the use of the enzyme.
The drug that attracts more of the enzyme wins.
If the opioid wins, your test may show too little of the drug in your system because it was metabolized or burned up quickly.
Conversely, f the other medication wins, your test may show too much of the opioid still in your system.
For more information on the enzymes most frequently involved in this interaction, read: Dangerous Opioid Drug Interactions
What to Do if Your Drug Test is Wrong
When a drug test comes back indicating a problem, most of the time a doctor will dismiss the patient - especially if they have a Treatment Agreement (sometimes called a Pain Contract or a Narcotics Contract). This can cause a serious problem for the patient who will face withdrawal if he/she can’t get the medication they need.
If this happens to you, try to talk to your doctor, explain why you think the test was wrong and request another more accurate test, like a blood or hair test. However, if the doctor won’t talk to you or consider your request, there are other steps you can take. Attorney Megan Oltman wrote a very good article addressing this problem: What to Do if Your Doctor Refuses to Treat You
Karen is the co-founder of the National Fibromyalgia Association. She wrote for HealthCentral as a patient expert for Pain Management.