Evaluation of oral fluid microsampling as a urine surrogate matrix in substance use disorder care: clinical...

Toxicological monitoring in addiction treatment centres routinely relies on urine analysis to assess substance use, abstinence, and opiate agonist therapy adherence. However, collecting urine presents two major limitations: potential privacy concerns due to supervised collection, and delays caused by the need for spontaneous urination. Oral fluid has been proposed as an alternative matrix to address these issues, despite its shorter detection window. This study evaluates the clinical applicability and analytical performance of oral fluid toxicological screening, using volumetric absorptive microsampling device, in patients with substance use disorders in an addiction treatment centre.

Fifty paired urine and oral fluid samples were collected. First, urine immunoassays were compared with oral fluid screening by high-performance liquid chromatography hyphenated to high resolution mass spectrometry to assess drug detectability, focusing on amfetamines, benzodiazepines, buprenorphine, cannabis, cocaine, ecstasy, methadone, and opiates. The mass spectrometry screening results from both matrices were then compared, and the analysis was extended to pharmaceuticals.

Forty-five (90%) patients rated the method change acceptable or very acceptable, compared to 14 (28%) who rated urine collection as acceptable or somewhat acceptable. Screening agreement between matrices exceeded 88%. Benzodiazepines were among the least detectable in oral fluid. On the contrary, for cocaine and cannabis, detection windows appeared longer in oral fluid.

Oral fluid collection offers clear advantages in terms of patient acceptability and ease of supervision, with the benefit of reducing the risk of sample adulteration compared to urine. High-resolution mass spectrometry provides the sensitivity required for reliable toxicological monitoring while remaining cost-competitive compared with multiple immunoassays. This approach is particularly suitable for frequent users and patients on chronic treatments.

Oral fluid microsampling has reliable toxicological results, combined with practical collection, patient satisfaction, reduced costs, and a lower risk of sample adulteration, highlights its clinical value. Although detection windows may differ from urine and turnaround times are longer than immunoassays, oral fluid remains a robust option for monitoring both drugs of abuse and prescribed treatments in this population.