Aaron C Miller, Philip M Polgreen

Injection drug use (IDU) and IDU-related infections have increased dramatically. However, the incidence of IDU-related infections may be underreported because drug use is not recorded in diagnostic records where associated infections are identified. Our goal was to estimate a more accurate incidence of IDU-related infections by including IDU-related infections not recorded at the time infections are diagnosed. We performed a retrospective cohort study using inpatient and emergency department visits from the Healthcare Cost and Utilization Project for California, Florida, and New York. We identified all patients diagnosed with bacteremia or sepsis, endocarditis, osteomyelitis or septic arthritis, and skin or soft tissue infection. We estimated the incidence of IDU-related infections by identifying cases where drug use was recorded at the time of an infection and cases where drug use was not recorded at the time of infection but within 6 months before or after the infection diagnosis. We also analyzed factors associated with unrecorded IDU. There has been an increasing trend in the number of IDU-related infections. The annual number of IDU-related infections increased between 105% and 218% after incorporating infections in which drug use was unrecorded. Factors associated with drug use being unrecorded included emergency department diagnosis, the level of hospital experience treating drug use, age <18 years, and having Medicare as the primary payer. More than half of all IDU-related infections may be unrecorded in existing surveillance estimates. There may be many missed opportunities to record, diagnose, or treat underlying drug abuse among patients presenting with IDU-related infections.