Effectiveness of Isoniazid Prophylaxis in Prevention of Tuberculosis in Child Household Contacts of Adults With Pulmonary Tuberculosis in Nairobi County, Kenya
Sub-Saharan Africa continues to document high burden of pediatric TB, driven by the HIV epidemic. The urban poor are at highest risk of infection. Infected children experience rapid disease progression and severer disease. Contacts‟ tracing and isoniazid prophylaxis is an effective prevention strategy, but has been administered inconsistently in most resource poor countries. Perceived obstacles have been sub-optimal effectiveness in view of continuous transmission and re-infections, as well as adherence and safety concerns. The objectives of this study was to evaluate the effectiveness of IPT in preventing TB related morbidity in children in household contact with adults with TB from informal settlements in Nairobi. A prospective longitudinal cohort study was done. Child contacts of recently diagnosed PTB smear-positive adults were enrolled. Recruitment started in December 2011 to July 2013. Consent was sought. A structured questionnaire was used to get information on source case TB treatment, socio-demographic characteristics and TB knowledge. Contacts underwent baseline clinical evaluations to exclude TB disease using clinical algorithms. TST, microscopy and histology were done whenever indicated. Contacts with chronic illnesses were excluded. A blood sample was obtained at baseline for liver enzymes assays and for PCR for HIV DNA. Contacts were then put on isoniazid for 6 months and followed up monthly for 1 year for new TB infection, and compliance and adverse events monitored. Qualitative data was provided by 2FGD and KIIs. Data was analyzed using SPSS. IPT acceptability was 320 out of 366(87.3%) of eligible source cases. Most (96%) were from poor social backgrounds, and 83.4% had below tertiary level of education. All source cases were on first line anti-TB treatment. Of 428 contacts screened, 6.3% were HIV positive. The baseline prevalence of latent TB was 92 (22.2%), while 14 (3.2%) had TB disease. IPT completion rate was 368 of 414 (88.8%). Overall compliance rate was 89%. IPT failure was documented in 6 (1.6%) cases, the relative risk of new TB disease in contacts on IPT was 0.49 (95% CI 0.21 -0.86). IPT effectiveness in preventing TB in exposed contacts was 50%. On multivariate logistic regression of factors influencing IPT failure, only weight faltering of contact was significant (p= 0.005). The leading programmatic challenges reported were too many hospital visits (65.2%) and difficulties in administering tablets to children (44.3%). Side effects were documented in 22.2%, mainly skin rash (12.5%), but significant hepatotoxicity occurred in only 3(0.08%). In conclusion, child TB is prevalent in exposed contacts in informal settlings. Contact screening and IPT is an effective, acceptable and safe child TB prevention strategy for exposed child contacts in these settings, however its implementation is fraught by various social and programmatic challenges minimizing overall benefits realized. Therefore, there is need to prioritize these children in informal settlements in TB screening programs. Furthermore, linkage of IPT strategy to nutrition interventions programs, and the provision of minimal adherence support to households could greatly optimize overall effectiveness attained.