Elsie Yu CLN ask the Expert July 2015

Why might some providers want to use point-of-care (POC) urinary drug screen testing in pain management clinics?

A:The most common reasons are convenience and fast turnaround time. Having immediate test results fosters patient engagement and satisfaction by reducing wait time and enabling practitioners to provide immediate consultations. The positive versus negative screen result is also easy for providers and patients to understand.

Another reason is cost. In the eyes of general practitioners, it is cheaper to purchase urinary drug test cups than to send a test to a central or reference laboratory. However, proper pain management testing often requires additional mass spectrometry–based drug testing. There is also a cost associated with managing POC urinary drug testing, which includes quality assessments of test kits, personnel training, proper result documentation, etc. As a result, POC urinary drug testing can be challenging to implement without lab support, and in clinics where there is high turnover among supporting staff such as nurses.

What are the clinical needs for drug testing in pain management clinics? Can these needs be met by POC urinary drug screen testing? Drug testing in pain management clinics is used to determine: (1) whether the patient is taking the pain medication as prescribed versus diverting it; and (2) whether the patient is abusing other substances.

To address the above needs, a POC urinary drug screen test must be able to detect the pain medication of interest and accurately identify any drugs of abuse.

Unfortunately, POC urinary drug screen testing has a limited ability to do these things. It is a screening tool only, and can produce false-positive or false-negative results due to the testing methodology. The cutoff concentration may also be too high in some cases for pain management use. Thus, any screening result that does not match the patient’s prescribed medication must be confirmed by mass spectrometry before the patient can be accused of non-compliance. However, many providers do not understand the presumptive nature of these test results and want to act on them immediately.

In addition, the drug of interest may not be screened by the POC test. For example, most opiate screens on the market primarily detect morphine and codeine. Depending on the assay used, hydrocodone and oxycodone may or may not be included. Some opioids, such as fentanyl, buprenorphine, tapentadol, and tramadol, are also not routinely detected by POC urine tests. However, this is not common knowledge to most providers. To many, if the opiate screen is negative, it means the patient is not taking the pain medication. Sadly, I have encountered cases in which patients were wrongfully dismissed from pain management programs because a test result was misinterpreted.

Another pitfall of POC urinary drug testing is that it cannot differentiate between the parent drug and its metabolite(s), which is critical for identifying diverting cases in which patients try to cheat the urine drug test by dissolving their medication in their urine sample. In those cases, high amounts of parent drug are present without any metabolite(s).

Lastly, POC urinary drug testing does not provide quantitative results. Therefore, one cannot determine if the patient’s dosages are supratherapeutic.

In conclusion, the utilization of a POC urinary drug screen test in a pain clinic is very limited and the information it provides is often not sufficient to enable proper patient consultation. Because most providers need assistance in interpreting toxicology tests, the use of POC urinary drug screening is likely to cause more confusion. Our institution addresses this problem with a pain management compliance test that offers decision support for pain management drug testing.

Hoi-Ying (Elsie) Yu, PhD, DABCC, FACB, is the system director of toxicology and point-of-care testing and associate director of chemistry at Geisinger Medical Laboratories in Danville, Pennsylvania. +Email: heyu@geisinger.edu