Predictors of contact tracing completion and outcomes in tuberculosis: a 21-year retrospective cohort study.

Setting: Birmingham, UK, 1990-2010.

Objective: To identify predictors in contacts for completion of screening and of a positive screening outcome, i.e., a diagnosis of latent tuberculous infection (LTBI) or active tuberculosis (TB).

Design: A retrospective cohort study of TB notifications for a European city.

Results: A total of 46,158 contacts were identified from 7365 index cases. Over the study period 17,471 (40.9%) failed to complete screening. Active TB or LTBI was diagnosed in 2220 (7.0%) contacts of cases of pulmonary TB (PTB) and in 222 (2.7%) contacts of cases of extra-pulmonary TB (EPTB). The proportion of contacts offered LTBI treatment increased (P < 0.001) over the study period. Age, ethnicity, sex and use of interferon-gamma release assays (IGRA) were the most important predictors of screening completion, with working age adult males who were Black or from the Indian subcontinent least likely to complete. Age, smear positivity status of the index case and IGRA usage were the most important predictors of a positive screening outcome (active TB or LTBI diagnosed).

Conclusion: Contact tracing of both PTB and EPTB index cases is useful for active case finding. The findings of this study can be used to target screening and improve the effectiveness and efficiency of local contact tracing programmes.