The Patient Scenario
A patient has been prescribed oxycodone for almost one year. His prescription has been increasing in dose in response to his reported pain. At his last visit, when the patient again asked the physician to have the oxycodone dose increased as his pain had considerably worsened, the physician, before increasing the dose, ordered a UDT immunoassay test which included opiates.
Immunoassay test to include opiates at reference laboratory
The Test Results
Urine drug test results were reported negative for opiates.
The Test Interpretation
The physician is not certain how to interpret the test findings and decides to discuss the results with the patient. He requests the patient be seen within the next 48 hours.
But before the patient can be seen again, the physician receives word that his patient was brought by ambulance to the emergency department in a comatose state and was admitted to ICU and is now on a ventilator.
The ICU attending physician indicates that preliminary toxicology confirms a solitary oxycodone overdose.
Oxycodone is a semisynthetic opiate. It is more difficult to detect oxycodone using a typical urine screen profile for natural opioid (“opiate,” ie, morphine and codeine) detection.
Unlike the regulated testing paradigm (ie, “Workplace Testing”) where the majority of samples are expected to be negative, clinical drug testing deals with a donor population, the vast majority of whom are appropriately positive for prescribed members of common drugs of misuse. For this reason, simple class detection (ie, “opiates”) is rarely sufficient to identify aberrant behavior through UDT. It now becomes important what drug is resulting in the positive result, not simply a class positive report.
Oxycodone is best detected when cut-off values are set low (100 ng/mL) using a specific immunoassay test. If not, the test results may be reported as negative, as was the case with this patient. A urine drug test to isolate oxycodone must be ordered with the drug of interest listed in the testing panel and should be ordered by requesting “limit of detection” testing.
It was later discovered that the patient had six separate prescriptions for oxycodone written by six different physicians. He had been doctor-shopping to satisfy his growing need for the drug.
In spite of the patient taking copious amounts of oxycodone, the drug was never detected because the test used (“opiate immunoassay”) is relatively insensitive to the oxycodone molecule. Had a specific oxycodone immunoassay test result truly been negative, the differential diagnosis would have included sample substitution, drug binging or diversion.
While it is clear that this patient was misusing oxycodone, there is no evidence to suggest or confirm drug diversion although this remains a possibility.
Unfortunately, regardless of the apparent motive, obtaining or seeking to obtain controlled substances through fraudulent means is a criminal act.
It is important to rely on methods other than just UDT to determine aberrant drug-taking behaviors or to demonstrate therapeutic compliance.
Unfortunately, all risk management strategies require a level of mutual trust and honesty that clearly was not present in this case.
The Final Outcome
The patient eventually recovered from his acute overdose and was transported to a tertiary center for assessment and care of his substance use disorder. Although the patient responded well to this treatment, future management of his chronic pain with controlled substances would be problematic for the foreseeable future. Unfortunately, such criminal actions, regardless of apparent motivation, can be devastating to any doctor-patient relationship. For this reason, it may be in the best interest of all parties for this patient to seek medical care elsewhere at a tertiary level center, if available.
Regardless of the primary class of drug, it is important to use specific tests, where they exist, to assess compliance with prescribed medications.
In the absence of an honest doctor-patient relationship, even the most sophisticated risk management strategies may fail.