Housing insecurity and lack of public assistance are risk factors for tuberculin skin test conversion among persons who use illicit drugs in New York City.

BACKGROUND

Persons who use illicit drugs are at increased risk of new tuberculosis (TB) infection. We conducted a prospective cohort study to assess rates and risk factors for tuberculin skin test (TST) conversion among persons with a history of illicit drug use, who were enrolled in a methadone program and had a negative baseline 2-step TST (eligible participants).

METHODS

TST and standardized interviews were administered to 401 eligible participants from 1995 through 1999, every 6 months for a 2-year follow-up time. Analyses were conducted in 2006.

RESULTS

A total of 1,447 repeat TSTs were performed during 843 person-years of follow-up (median: 2.0 years). The TST conversion rate was 3.7 per 100 person-years. In multivariate analysis, participants who converted were more likely to report ever having been homeless (HR, 2.4; 95% CI, 1.2-5.0) or ever having lived in a homeless shelter (HR, 2.4; 95% CI, 1.2-4.9) at the baseline interview, and less likely to have reported receiving public assistance since the last study visit (RR, 0.15; 95% CI, 0.07-0.32).

CONCLUSIONS

This is the first study utilizing 2-step TST at baseline to measure the incidence of TST conversion among persons who use illicit drugs. Controlling for homelessness, persons with a lack of current public assistance was identified as a risk factor for TST conversion. These individuals may most benefit from annual tuberculin skin testing.