Abstract
OBJECTIVES: Self-report and biospecimen testing to assess drug exposure have limitations. Surface testing of personal objects (e.g., mobile phones) may provide complementary information about drug exposure, particularly when there is discordance between biospecimen results and self-report. We examined whether mobile phone swab testing, alongside self-report and oral fluid data, could provide information regarding drug exposure among nightlife attendees-a population with high prevalence of party drug use. We also examined whether detection could inform situations in which a drug is detected in oral fluid but not reportedly used. METHODS: In 2025, we assessed self-reported drug use and analyzed oral fluid and swabs of mobile phones from 127 adults attending nightclubs in New York City. We compared the prevalence of detection of cocaine, ketamine, 3,4-methylenedioxymethamphetamine (MDMA), and 4-methylmethcathinone (4-MMC) across the three modes of collection. RESULTS: Cocaine was detected on 26.8% of phones, followed by ketamine (22.0%), 4-MMC (3.1%), and MDMA (2.4%). When classifying phone detection, reported past-48-hour use and oral fluid detection of cocaine and ketamine demonstrated high specificity (0.85-0.91), but lower sensitivity (0.37-0.73). Among participants with oral fluid positivity after not reporting use, 33.3% and 17.1% of these discordant cases had ketamine and cocaine detected on their phones, respectively. CONCLUSIONS: Phone swab results often align with self-reported use and, less consistently with biologically confirmed exposure. However, drugs detected on phones may reflect less recent use or unintentional environmental sources contributing to oral fluid detection, supporting the role of phone swabbing as a complementary tool for detecting possible drug exposure.