Factors associated with loss to follow-up in a large tuberculosis treatment trial (TBTC Study 22)

Loss to follow-up in clinical trials compromises achievement of study goals. We evaluated factors associated with loss to follow-up after completion of treatment phase in a large tuberculosis treatment trial (TBTC/USPHS Study 22) in the U.S. and Canada.

Patients who were lost to follow-up were compared to those who reached a study end-point or successfully completed follow-up. A generalized estimating equation model was used to combine patient-specific and site-specific factors.

Of 1075 patients enrolled, 965 (89.8%) reached a study end-point, died, or completed the 2 year post-treatment follow-up phase, and 110 (10.2%) did not. Multivariate analysis showed the following factors to be independently associated with loss to follow-up: birth outside USA/Canada (OR 2.07, 95% CI 1.25-3.40, p=0.005), history of homelessness (OR 1.94, 95% CI 1.00-3.80, p=0.05), enrollment at a health department (OR 2.71, 95% CI 1.27-5.79, p=0.010), and use of any kind of incentive (cash/cash equivalent) during treatment phase (OR 3.04, 95% CI 1.73-5.33 p=0.0001).

Cultural or linguistic factors and lack of stable housing contribute to loss to follow-up. Attention to these factors could improve long-term retention in clinical trials. Enrollment at a health department and use of incentives during treatment phase may be markers for other factors leading to loss to follow-up.