Risk factors associated with TB infection among household contacts of microbiologically confirmed pulmonary TB patients in three high TB burden countries.

Abstract

Background: Although tuberculosis (TB) preventive therapy (TPT) guidelines support testing for TB infection (TBI) in household contacts (HHCs), this adds operational complexity and cost and has often been abandoned. To understand utility of testing, we determined prevalence and risk factors for TBI and TPT eligibility among HHCs.

Methods: In a cross-sectional study conducted from July 2021-September 2022 in Lesotho, South Africa, and Tanzania, we enrolled people with microbiologically-confirmed pulmonary TB (PWTB) and their HHCs. HHCs were screened and tested for TB and TBI using Xpert Ultra and QuantiFERON-TB-Gold-Plus, respectively. Generalised linear modelling was used to determine factors associated with TBI, using robust standard errors. TPT eligibility was determined using World Health Organisation criteria.

Results: We enrolled 342 PWTB and 964 HHCs: 61.9% (597/964) were female with a median age of 18 years (interquartile range: 8-39). Overall, TB prevalence was 3.4% (25/739, 95% Confidence Interval (CI): 2.2-4.9), while TBI prevalence was 48.7% (348/714, 95%CI: 45.0-52.5). Having TBI increased with age per year (adjusted Odds Ratio (aOR) 1.02, 95%CI: 1.01-1.03), being from Lesotho (aOR 1.82, 95%CI: 1.04-3.20), previous TB history (aOR 2.25, 95%CI: 1.05-4.79), and being HIV negative (aOR 2.30, 95%CI: 1.31-4.04). Overall, 62.2% (518/833, 95%CI: 58.8-65.5) were eligible for TPT.

Conclusion: Almost half of TB exposed HHCs aged ≥5 years had TBI. Approximately two thirds of HHCs were eligible for TPT, implying that providing TPT without prior testing for TBI may be warranted in this population. Further work on cost-effectiveness is warranted when new tests become available.