#4: POCs: Screening vs Confirmation

February 22, 2019 Archived Blog Posts

I received a very appropriate text the other day from a sharp employee with questions regarding a patient’s result.  It read, “Our POC (Point of Care) in house reflected suboxone as present, then the lab shows no suboxone. So I’m curious.”  Pulling up the report, the patient’s screen was positive for Buprenorphine, Opiates and Benzodiazapines.  The confirmation was positive for tramadol and O-des-methyltramadol only.  So what happened?….Times up!  First, the confirmation tells us the patient is taking Tramadol, which was not listed as prescribed.  The presence of tramadol commonly produces a false positive screening test for Buprenorphine.  Secondly, the statement that “the in house reflected Suboxone as present” is not accurate.  The only thing present in house was Buprenorphine, which is one of the active ingredients in Suboxone.  The other active ingredient is Naloxone.  Without both being present the only thing that can be stated as fact is the patient tested positive for Buprenorphine on the screen.  Finally, what caused the false positive, in house, for the Benzodiazapine?  Since no other drugs were listed as prescribed other than Suboxone, I have no clue, however the confirmation done in the lab proved there were no Benzodiazapines present in the urine.  Once again this is a classic example of why you must order confirmation testing done and should NEVER rely solely on the drug screening test to confront a patient!!

You will notice in the above paragraph I put the words screen and confirmation in bold black.  Of course there is always a method to my madness.  There is a major difference between a drug screen test and a confirmation or definitive test.  Yet even scholars use the words drug screen too liberally.  A drug screen refers to an Enzyme Linked Immunoassay (EIA) test.  This is what a panel cup test is, or some of you perform EIA screening on an Immunoassay Analyzer in your clinic.  These two testing methods are screens and unfortunately there is a significant problem with “cross-reactivity” in EIA testing.  To put it simply, leaving out the complex chemistry, there are a lot of false positives and false negatives with an EIA test.  Confirmation or definitive testing is performed in our lab on a LC/MS/MS.  This test actually separates and analyzes the different molecules in a drug sample to give you the definitive drugs and metabolites present in the urine sample.  The accuracy of confirmation testing on an LC/MS/MS is undeniable.  Let’s all start being more specific when referring to drug testing.  Do you mean drug screening or drug confirmation?

On a side note, for those of you in the Substance Use Disorder (SUD) treatment world, I recommend you see the movie, “Beautiful Boy.”  It is well done and shows the side of stimulant addiction which is on the rise.  If you are not familiar with methamphetamine use, this film explores that well.  If you know someone with SUD, encourage, support and love them.  There is always hope.  Thanks to all of you for your business.

Lance Benedict
President/CEO Industry Lab Diagnostic Partner