Evaluation of fentanyl test strips

AIM

The last few years dozens of opioids have appeared on the NPS market, with most substances being fentanyl derivatives. Some of these substances have potencies several thousand times that of morphine, and they have caused countless overdose deaths worldwide. In Europe it is less clear to what extent fentanyl is present in the traditional heroin chain. (1–3)

The practice of fentanyl urine test kits for detecting the presence of fentanyl and fentanyl analogues in drug samples has been in use for some time. While preliminary results have been promising, it is important to investigate several specific aspects: Specificity, how well do the test strips detect fentanyl analogues, minimum detectable limit, false negative and false positive occurrence.

Once research evidence becomes strong, the promotion of fentanyl test strips to reduce overdose risk can be implemented further. Confirmation of the feasibility and validation of fentanyl test strip technology could boost this as a drug checking strategy to address the fentanyl crisis.

OUTCOME

In summary the fentanyl test strips tested displayed a broad selectivity, detecting a vast range of fentanyl analogues present on the recreational drug market. None of the fentanyl strips were affected by the presence of heroin, illicit or other pharmaceutical drugs.

The tests have a few limitations:

• The test strips give no indication on the concentration level of the detected fentanyl (analogues).
• Very high concentrations of various non-fentanyl compounds can give false positives. To avoid this situation and as a practical guidance for testing samples with FTS, we would recommend diluting the sufficient amount of the sample as a grain of rice into 10mL of water. Over diluting is not a problem, the FTS is sensitive enough for fentanyl detection. The immunoassay test strips are a reliable detection method for fentanyl at low concentrations and complex matrices.
• False positive results for MDMA and methamphetamine can occur at a concentration level of 20mg/mL.
• A limitation for the test strips was the low sensitivity for detecting ultra-potent fentanyl analogue carfentanil (cut-off 200 ug/mL).
• No detection possible of highly potent NPS opioids, such as metonitazene, fluonitazene, butonitazene and etonitazepyne

If you would like to read the full report, please contact margot.balcaen@sciensano.be