Prevalence, incidence and determinants of QuantiFERONTM positivity in South African schoolchildren.

Background: TB control requires the understanding and disruption of TB transmission. We describe prevalence, incidence and risk factors associated with childhood TB infection in Cape Town, South Africa.

Methods: We report cross-sectional baseline and prospective incidence data from a large trial among primary school children living in high TB burden communities. Prevalent infection was defined as QuantiFERON™-TB Gold Plus (QFT-Plus) positivity as assessed at baseline. Subsequent conversion to QFT-Plus positivity was measured 3 years later among those QFT-Plus-negative at baseline. Multivariable logistic regression models examined factors associated with TB infection.

Results: QuantiFERON-positivity at baseline (prevalence: 22.6%, 95% CI 20.9-24.4), was independently associated with increasing age (aOR 1.24 per additional year, 95% CI 1.15-1.34) and household exposure to TB during the participant's lifetime (aOR 1.87, 95% CI 1.46-2.40). QFT-Plus conversion at year 3 (12.2%, 95% CI 10.5-14.0; annual infection rate: 3.95%) was associated with household exposure to an index TB case (aOR 2.74, 95% CI 1.05-7.18).

Conclusion: Rates of QFT-diagnosed TB infection remain high in this population. The strong association with household TB exposure reinforces the importance of contact tracing, preventative treatment and early treatment of infectious disease to reduce community transmission.