Detection of benzodiazepines in the unregulated drug supply using point of care and confirmatory drug checking technologies: A validation study

Abstract

Objective

Benzodiazepine adulteration in British Columbia's (BC) unregulated opioid supply has risen. Given the health risks associated with co-ingestion of opioids and benzodiazepines, accurate detection of benzodiazepines using point-of-care drug checking technologies is critical. This study aimed to validate the use of Fourier-transform infrared spectroscopy (FTIR) and benzodiazepine immunoassay strips compared to gold standard laboratory technologies.

Methods

From October 2018 to November 2023, drug samples submitted to harm reduction sites in BC were analyzed using FTIR and benzodiazepine immunoassay strips. A subset of these samples was sent for confirmatory analysis using quantitative nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry, and/or liquid chromatography-mass spectrometry. We calculated measures of diagnostic accuracy (e.g., sensitivity, specificity) for the point-of-care technologies.

Results

Of 1922 samples with point-of-care and confirmatory results, 390 (20 %) tested positive for a benzodiazepine. FTIR sensitivity was 26 % (95 % confidence interval [CI]:21–30 %) and specificity was 99 % (95 % CI:99–100 %). Immunoassay strip sensitivity was 67 % (95 % CI:62–72 %) and specificity was 82 % (95 % CI:79–85 %), respectively. When FTIR and immunoassay strip results were combined, sensitivity was 75 % (95 % CI:70–79 %) and specificity was 82 % (95 % CI: 79–84 %). When etizolam was excluded, the sensitivity and specificity of immunoassay strips were 98 % (95 % CI:94–99 %) and 83 % (95 % CI:81–86 %), respectively.

Conclusions

FTIR did not consistently detect the presence of benzodiazepines and related compounds at point-of-care. However, sensitivity improved when FTIR was combined with immunoassay strips, underscoring the importance of using both technologies in tandem. As etizolam is not a true benzodiazepine, it poses considerable challenges using existing point-of-care drug checking technologies.