When to Integrate Point-of-Care Drug Screens with Definitive Lab Tests

NATIONAL HARBOR, Md. — Pain management opinions about drug testing patients with chronic pain varies widely, ranging from clinicians who believe it is unethical and unconstitutional to perform any drug testing to those who believe broad spectrum testing should be performed at every visit. 

However, there is no debating that as regulations continue to be strengthened in efforts to combat opioid misuse, drug screening is increasingly becoming part of the standard of care in pain management. 

Practitioners should be familiar with the strengths and limitations or urine drug screening, as well as when to request more definitive laboratory tests, according to a speaker at the American Academy of Pain Management 2015 meeting.

“Drug screening is not one size fits all. The type and frequency of drug testing should be tailored to the individual patient,” said Gary M. Reisfield, MD, an assistant professor in the divisions of addiction medicine, pain medicine, and forensic psychiatry at the University of Florida College of Medicine in Gainesville. 

It is generally considered good clinical practice to perform a drug screen on any new patient before commencing opioid treatment, Dr. Reisfield advised. Other instances in which drug screening should be considered include change in patient behavior, grooming, or affect; discrepancies in pill counts; concerning physical exam findings (track marks suggesting intravenous drug use); and if concerns are expressed by collateral sources such as patient friends and family. 

Point-of-Care or Laboratory-Based Drug Testing?

“Results for laboratory-based drug tests can take a few hours at least, but POC immunoassay results are available in minutes,” said Dr. Reisfield. “This means you can sit with your patient at the time you performed the test and look him or her in the eye to ask about the meaning of results.”

However, there are several POC testing limitations including a more limited selection of drugs and metabolites for which can be tested and issues related to test specificity and sensitivity with certain drugs and metabolites. “Because of better quality control, results from laboratory-based tests are more uniform, and typically there is wider selection of analytes,” he explained. 

Dr. Reisfield described 7 scenarios in which pain management practitioners should request additional, definitive laboratory testing beyond a POC test:

When a POC screening result dose not comport with a patient report. This applies to screens that are positive, but in which the patient denies use, and also screens that are negative, but in which a patient claims adherence to the prescribed medication. In the first case, the clinician should request confirmatory testing for the drug or drug class. In the second case, confirmatory testing is needed for the drug or drug metabolite.

The clinician needs to determine the presence of a drug or metabolite for which there is no available screening immunoassay to confirm for the drug or metabolite of interest. (ie fentanyl, K2, spice, carisoprodol, tramadol).

The clinician needs specificity that a class-specific assay cannot provide to confirm for the drug or metabolite of interest.

A quantitative result is needed for a drug or metabolite following serial use to ensure cessation or to rule out drug spiking in a urine specimen.

A screening result is appropriately negative, but pretest probability of drug use is high in a given patient.

The specimen appears to be adulterated or there is a high pretest probability of adulteration to perform specimen validity testing. Clinicians may also consider observed collection of the second specimen, Dr. Reisfield recommended.

The test will have important consequences, such as termination of the provider-patient relationship or inability of the patient to obtain opioid medications. In this case, the clinician should consider confirming the presumptive positive or negative screening results.

“If there is a discrepancy between what your patient says and results on a point-of-care drug test, the tie goes to the patient until proven otherwise. In these instances, it is imperative to send the sample for laboratory testing,” said Dr. Reisfield.

Reference

1. Reisfield GM. “Essentials of point-of-care urine drug testing in pain medicine.” Presented at: AAPM 2015. Sept. 17-20; National Harbor, Maryland.