The effectiveness of contact investigation among contacts of tuberculosis patients: a systematic review and meta-analysis.

Background: We aimed to evaluate the effectiveness of contact investigation in comparison with passive case detection alone, and estimate the yield of co-prevalent and incident tuberculosis (TB) and latent TB infection (LTBI) among contacts of patients with TB.

Methods: A systematic search was undertaken of studies published between 1 January 2011 and 1 October 2019 in the English language. The proportion of contacts diagnosed with co-prevalent TB, incident TB and/or LTBI was estimated. Evaluation of the effectiveness of contact investigation included randomised trials, while the yield of contact investigation (co-prevalent/incident TB and LTBI) was assessed in nonrandomised studies.

Results: Data were extracted from 244 studies, of which 187 studies measured the proportion of contacts diagnosed with TB disease and 135 studies measured LTBI prevalence. Individual randomised trials demonstrated that contact investigation increased TB case notification (relative risk 2.5, 95% CI 2.0-3.2) and TB case detection (OR 1.34, 95% CI 0.43-4.24) and decreased mortality (relative risk 0.6, 95% CI 0.4-0.8) and population TB prevalence (risk ratio 0.82, 95% CI 0.64-1.04). The overall pooled prevalence of TB was 3.6% (95% CI 3.3-4.0%; I=98.9%, 181 studies). The pooled prevalence of microbiologically confirmed TB was 3.2% (95% CI 2.6-3.7%; I=99.5%, 106 studies). The pooled incidence of TB was highest in the first year after exposure to index patients (2.0%, 95% CI 1.1-3.3%; I=96.2%, 14 studies) and substantially lower 5 years after exposure to index patients (0.5%, 95% CI 0.3-0.9%; one study). The pooled prevalence of LTBI among contacts was 42.4% (95% CI 38.5-46.4%; I=99.8%, 135 studies).

Conclusions: This systematic review and meta-analysis found that contact investigation was effective in high-burden settings. The higher pooled prevalence estimates of microbiologically confirmed TB compared with previous reviews suggests newer rapid molecular diagnostics contribute to increased case detection.