Once more we will delve into the minutiae of an issue…this time into testing patients who are prescribed opioids to ascertain if they are taking the prescribed medications, and if there is evidence they are consuming other licit and/or illicit drugs.
(full disclosure – Millennium Health, the largest toxicology testing company, is a consulting client)
All guidelines suggest/encourage/require testing of patients prescribed opioids.
There are two types of urine drug tests – qualitative, where a cup test simply indicates if a drug is or is not present, and quantitative, which is much more accurate and must be done in a lab.
I’m surprised at the continued use of qualitative tests as they are notoriously unreliable; research indicates the cup test failed to show benzodiazepines were present for 28% of specimens, and cocaine for fully half of specimens evaluated – and false negatives and positives for other drugs are much higher than one would expect. These “false negatives” are obviously misleading; the usefulness of cup tests is further compromised by how easy they are to fool. (there are about a gazillion web pages that provide info on passing a cup test…)
Except, if your sample gets sent to a lab for quantitative testing. It is much harder to fool good lab testing because the testing equipment:
- uses much lower cutoff levels for drugs, thereby finding more positives than cups do;
- tests for metabolites – the chemicals created by your body after it processes the drugs: metabolites show you’ve actually taken the drug
- checks for certain chemical markers that can indicate if the urine is fake or from another person (or, in some cases, another animal)
There’s much more to this; warning, if you start looking around on the web, you’ll find some incredible stories and myths and tales about folks allegedly passing tests; great for entertainment but very easy to become mesmerized for hours.
I recently reviewed data from a very large sample, specifically looking for data about cup results vs lab (quantitative) results. The analysis was rather disturbing…Cup tests missed:
- 45% of opiates (cup reported no opiates, lab reported opiates)
- 44% of benzodiazepines
- 28% of marijuana
Cup tests also indicate drugs are present when the lab tests show they are not, false positives occurred in:
- 27% of reported opiates
- 69% of antidepressants
- 100% of PCP
What does this mean for you?
Be very careful about basing decisions on cup tests – even if they show there aren’t any anomalies or “unexpected” results.