Effectiveness of Isoniazid preventive therapy on incidence of tuberculosis in adult people living with HIV in selected Districts of Rwanda

Abstract

Tuberculosis (TB) is a common complication and leading cause of death in people living with HIV infection. In Rwanda, TB is the main opportunistic infection and it is the leading cause of death in HIV infected patients (Rwanda Ministry of Health, 2005). Whereas some literature have shown that the use of Isoniazid as a prophylaxis reduced the TB incidence in HIV/TB co-infected patients by 70–90 percent (Whalen et al., 1997; Gordin et al., 1997) others yielded conflicting results. For example a study from Brazil revealed that IPT mostly worked with ART whereby ART alone was independently associated with 59 per cent reduction in tuberculosis incidence, while the effect of IPT alone was no longer significant (Golub et al., 2007). Despite good evidence that Isoniazid Preventive Therapy (IPT) reduces the incidence of TB among people with HIV infection, implementation of IPT is low at the global perspective. Although, Rwanda is among few countries in the region implementing six months IPT strategy, but there is no published literature on its effectiveness in the country. This gap called for further studies to extend the knowledge on IPT, to support its implementation and to relate the known to country‘s context. Therefore the present study intended to establish whether IPT reduced the incidence of active TB in people living with HIV (PLHIV). This was a retrospective cohort study design using medical records of PLHIV from six health facilities in three districts of Rwanda. The period of study extended between 1st August, 2011 and 31st January, 2014. Out of 2172 PLHIV, 1,086 were on IPT and 1,086 were not. Survival analysis and Poisson regression with SPSS version 20.0 were used to compare rates of TB and factors contributing to it in PLHIV on IPT to those not on IPT. The overall TB incidence was 1.131 cases per 100 person-years (PY) [95 confidence interval (CI) 0.98-1.44]. The incidence rate of TB in patients on IPT was significantly lower than those who were not on IPT (0.56/100PY vs 2.04/100PY) and Incidence Rate Ratio (IRR) was 0.275 [95% CI 0.152-0.493]. Multivariate Cox proportional hazard model revealed 73 per cent reduction in TB risk among patients who received IPT. Among IPT completers, the risk of developing TB reduced up to 87.5 per cent (HR=0.125 P value<0.00). Being on ART, having CD4 cell count >350, HIV clinical stage 1 and 2 and high income, were factors contributing to lower incidence of TB among PLHIV on IPT. 5 By comparing the time of TB occurrence among PLHIV who took IPT with those who did not, the present study showed that the protective effect of IPT seemed to be gradually lost over time. It did not decline as rapidly as it has been reported in patients not on IPT. The use of Isoniazid in People Living with HIV was associated with low incidence of Tuberculosis.