Effectiveness of Isoniazid Preventive Therapy on the Incidence of Tuberuculosi in People Living With HIV/Rwanda

Uwamahoro, Marie Claire

Purpose:

The purpose of this study was to evaluate the effectiveness of primary Isoniazid Preventive Therapy (IPT) on the incidence of active Tuberculosis (TB), in adult People Living with Human Immuno-deficiency Virus (PLHIV) in selected districts of Rwanda. Specifically the study was intended to (1) compare the incidence of active TB among adult PLHIV who took Isoniazid Preventive Therapy with those who did not take Isoniazid Preventive Therapy, (2) To identify the socio-demographic and clinical factors contributing to active tuberculosis in PLHIV on Isoniazid Preventive Therapy and (3) To compare the time of tuberculosis occurrence among PLHIV who took Isoniazid Preventive Therapy with those who did not.

Methods:

This was a retrospective cohort study design using medical records of People Living with Human Immuno-deficiency Virus (PLHIV) from six health facilities in three districts of Rwanda. Among these six health facilities, three are exclusively in a pilot programme providing Isoniazid Preventive Therapy in the whole country and other three are not. The period of study extended between 1st August, 2013 and 31st January, 2014. Out of 2172 PLHIV followed backward, 1,086 were on Isoniazid Preventive Therapy and 1,086 were not. Survival analysis and Poisson regression with SPSS version 20.0 were used to compare the rates of tuberculosis and factors contributing to TB in PLHIV on Isoniazid Preventive Therapy with PLHIV not on Isoniazid Preventive Therapy.

Results:

The overall tuberculosis (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. 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.

Conclusion:

The use of Isoniazid Preventive Therapy in people living with HIV was associated with a low Incidence Rate of tuberculosis. The results would indicate a need to scale up the program to other health facilities.