Setting: An urban tuberculosis (TB) clinic, The Gambia.
Objective: To identify patient characteristics associated with increased rates of defaulting from treatment, specifically knowledge and cost factors amenable to intervention.
Design: Prospective cohort study of TB cases at least 15 years of age commencing treatment, interviewed by semi-structured questionnaire and followed for attendance at thrice-weekly directly observed treatment (DOT).
Results: Of 301 patients, 76 (25.2%) defaulted from treatment and 25 did not return for treatment. The defaulting rate was higher among those who said they were uncertain that their treatment would work (HR 3.64; 95%CI 1.42-9.31, P = 0.007) and among those who incurred significant time or money costs travelling to receive treatment (HR 2.67; 95%CI 1.05-6.81; P = 0.04). These factors had differing effects with respect to time: uncertainty over treatment success was important in the first 90 days of treatment, while increased cost of travelling to the clinic was important after 90 days.
Conclusion: In The Gambia, risk groups for defaulting can be recognised at the start of treatment and are at highest risk at different times. Home-based self-administration of medications after 3 months of DOT should be considered as confidence in treatment success rises, and the costs of travelling to receive treatment start to take their toll.