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

## TL;DR

This study examines TB infection rates and risk factors in South African schoolchildren, finding high prevalence and a strong link to household TB exposure.

## Contribution

The study provides new insights into TB infection dynamics and risk factors in a high-burden community using longitudinal data from schoolchildren.

## Key findings

- Baseline QFT-Plus positivity was 22.6%, with increasing age and household TB exposure as significant risk factors.
- Annual TB infection rate was 3.95%, with household exposure to an index TB case strongly associated with conversion to QFT-Plus positivity.
- High TB infection rates underscore the need for contact tracing and early treatment to curb transmission.

## Abstract

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.

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.

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).

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.