Effect of Isoniazid preventive therapy on tuberculosis incidence and associated factors among Adult Patients Enrolled in ART in public health facilities at Ambo Town, Oromia, Ethiopia,2022. A retrospective Cohort Study.

Abstract

Background: Tuberculosis (TB) is one of the major causes of illness and death among people living with the Human Immunodeficiency Virus (HIV). So, the World Health Organization (WHO) has recommended Isoniazid Preventive Therapy (IPT) for HIV-infected patients to decrease tuberculosis (TB) related infection and death from the current prevalence with high HIV cases in our country Ethiopia which is estimated to be 13%. There is some information on the relation between TB incidence and INH with other factors like low CD4 count, BMI and intake of Co-trimoxazole preventive therapy among PLHIV. Objective: To Assess the Effect of isoniazid preventive therapy on tuberculosis incidence and associated factors among Adult Patients Enrolled in ART in public health facilities in Ambo Town, western Ethiopia, between 2016-2022. Methods: An institutional-based Six years’ retrospective study was conducted among 771(386=INH Exposed group and 385= Non-INH exposed group) adults on ART at health institutions in Ambo Town. The Sample size was determined using two population proportion formulas. A Simple random sampling technique was used to select patient records. Data were collected using a checklist and recorded on an electronic tool called Kobo-collect and exported to SPSS version 26.0 for further statistical analysis. Kaplan-Meier survival plots and the log-rank test was used to compare the crude effect in both the exposed and non-exposed groups on TB-free survival probabilities. Univariate analysis, Bi-variable and multivariable cox regression analysis were done. And also predicators variables of TB with a p-value of <0.25 were entered into multivariate cox regression analysis. Results: The incidence of TB among the Isoniazid-treated group was 0.2 per 100 person-years and 2.2 per 100 person-years in the non-isoniazid group. Patients who did not receive INH had (AHR= 8.9; 95% CI:2.52-31.61), patients who were WHO stage 3 had (AHR =15.5; 95 % CI :(6.55-30.47), Patients with CD4 count fewer than 100cells/µl had (AHR=4.33;95% CI:1.35-13.88), have higher risk of TB incidence. Isoniazid preventive therapy use was associated with a 90.7% (AHR= 0.093, CI=0.029- 0.31)) reduction in tuberculosis incidence. Conclusion and Recommendation: IPT use was associated significantly reducing tuberculosis incidence. In this study IPT showed a reduction in TB incidence of 90%. The incidence rate of TB was found to be 1.3 per 100 person- years. So, health care workers must strictly follow clients on providing INH and needs to counsel the patients on adherence to INH.