Abstract
BackgroundQuantiFERON-TB Gold In Tube (QFT-GIT) is a tool for detecting M. tuberculosis infection. However, interpretation and utility of serial QFT-GIT testing of pediatric tuberculosis (TB) contacts is not well understood. We compared TB prevalence between baseline and 6 months follow-up using QFT-GIT and tuberculin skin testing (TST) in children who were household contacts of adults with pulmonary TB in South Africa, and explored factors associated with QFT-GIT conversions and reversions.MethodProspective study with six month longitudinal follow-up.ResultsAmong 270 enrolled pediatric contacts, 196 (73%) underwent 6-month follow-up testing. The 6-month prevalence estimate of MTB infection in pediatric contacts increased significantly from a baseline of 29% (79/270, 95%CI [24–35]) to 38% (103/270, 95% CI [32–44], p<0.001) using QFT-GIT; prevalence increased from a baseline of 28% (71/254, 95%CI [23–34]) to 33% (88/263, 95%CI [21–32], p = 0.002) using TST. Prevalence estimates were influenced by thresholds for positivity for TST, but not for QFT-GIT. Among 134 children with a negative or indeterminate baseline QFT-GIT, 24 (18%) converted to positive at follow-up; conversion rates did not differ significantly when using more stringent thresholds to define QFT-GIT conversion. Older age >10 years (AOR 8.9 95%CI [1.1–72]) and baseline TST positivity ≥5 mm (AOR 5.2 95%CI [1.2–23]) were associated with QFT-GIT conversion. Among 62 children with a positive baseline QFT-GIT, 9 (15%) reverted to negative; female gender (AOR 18.5 95%CI [1.1–321]; p = 0.04] was associated with reversion, while children with baseline positive TST were less likely to have QFT-GIT reversion (AOR 0.01 95%CI [0.001–0.24]).ConclusionAmong pediatric contacts of adult household TB cases in South Africa, prevalence estimates of TB infection increased significantly from baseline to 6 months. Conversions and reversions occurred among pediatric TB contacts using QFT-GIT, but QFT-GIT conversion rates were less influenced by thresholds used for conversions than were TST conversion rates.
Highlights
In the wake of a significant HIV epidemic, South Africa has experienced a dramatic rise in the incidence of tuberculosis (TB) [1]
The 6-month prevalence estimate of M. tuberculosis (MTB) infection in pediatric contacts increased significantly from a baseline of 29% (79/270, 95%CI [24–35]) to 38% (103/270, 95% CI [32–44], p,0.001) using QuantiFERON-TB Gold In Tube (QFT-GIT); prevalence increased from a baseline of 28% (71/254, 95%CI [23– 34]) to 33% (88/263, 95%CI [21–32], p = 0.002) using TST
We previously reported a high prevalence of MTB infection as assessed by a single TST or QFT-GIT test, among children in South Africa who were household contacts of an adult with newly diagnosed pulmonary TB [11]
Summary
In the wake of a significant HIV epidemic, South Africa has experienced a dramatic rise in the incidence of tuberculosis (TB) [1]. As they have high rates of progression from latent tuberculosis infection (LTBI) to active TB disease and are at risk for severe forms of TB disease [2,3]. These issues underscore the need for early detection and diagnosis of M. tuberculosis (MTB) infection in children. We compared TB prevalence between baseline and 6 months follow-up using QFT-GIT and tuberculin skin testing (TST) in children who were household contacts of adults with pulmonary TB in South Africa, and explored factors associated with QFT-GIT conversions and reversions
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