Evaluation of Tuberculin Skin Test Positivity and Annual Risk of Infection among Children Visiting the Basic Health Unit, Kachi Shahani, Bhakkar

Abstract

Background: TB is still a major public health problem in Pakistan and children are at high risk of latent TB infection (LTBI). A lack of understanding of the burden and risk factors of LTBI in paediatric populations will hinder the effectiveness of TB control strategies. The objective of the study was to find out the prevalence of LTBI among children attending BHBU Kachi Shahani of District Bhakkar, Punjab, Pakistan and to look for risk factors associated with this infection.

Methods: The study was conducted by cross sectional approach that is hospital based study in the Basic Health Unit Kachi Shahani, Bhakkar in which 425 children age (1-15 years) were selected. Demographic details such as age, sex, residence and BCG scar were obtained by using a structured questionnaire. Tuberculin Skin Test (TST) was injected intradermally with 0.1 mL of purified protein derivative and induration was measured 48-72 hours after the injection. If any induration was ≥10 mm, this was treated as positive for LTBI. The data were analysed using SPSS version 25. The prevalence was reported with 95% confidence intervals, and the Annual Risk of Infection (ARI) was estimated using the formula ARI = 1 − (1 − P)^(1/a). Chi-square tests and multivariable logistic regression were used to test for associations with demographic factors in TST-positive children.

Results: Of the 425 participants, the majority were aged 6-10 years (41.4%), male (52.5%), and from rural areas (65.4%). In 82.4% of children, BCG scar was observed. The overall TST positivity rate was 16.9% (72/425) and it was continuing to rise with age; the rate was 8.5% in children aged 1-5 years, 15.3% in children aged 6-10 years and 26.7% in children aged 11-15 years. The risk of infection was estimated at 2.2% per year. Multivariable logistic regression showed that children aged 11-15 years had significantly higher odds of being TST positive than did the children aged 1-5 years (aOR 3.12, 95% CI: 1.45-6.70, P=0.003). Children who did not have a BCG scar were also significantly more likely to test positive for TST (aOR 2.41, 95% CI: 1.31-4.44; P=0.005). Sex (aOR 1.18, 95% CI: 0.72-1.92, P=0.507) and place of residence (aOR 1.56, 95% CI: 0.90-2.69, P=0.108) were not significantly associated with TST positivity.

Conclusions: The study shows that the overall prevalence of latent tuberculosis infection is high among the children of Bhakkar (16.9%) while the Annual Risk of Infection is estimated to be 2.2%. Being older (11–15 years) was a significant independent risk factor for LTBI, as was the absence of a BCG scar. These indicate the need to urgently strengthen TB control efforts, particularly regarding contact tracing, improving TB preventive therapy for older children and adolescents, and maintaining high BCG vaccination coverage, in this high TB burden context. Ongoing monitoring and targeted interventions are key to curb transmission of TB and LTBI in children in Pakistan.