Assessing the Impact of Isoniazid Preventive Therapy (IPT) on Tuberculosis Incidence and Predictors of Tuberculosis among Adult Patients Enrolled on ART in Nekemte Town, Western Ethiopia: A Retrospective Cohort Study

Abstract

Background. Isoniazid preventive therapy is a prophylactic treatment used in the prevention of active tuberculosis. It is known to be most effective in preventing tuberculosis in patients with positive tuberculin skin test. Methods. A retrospective cohort study centering on two institutions in Nekemte town, Western Ethiopia, was employed. Secondary data of 600 medical records were analyzed by Cox regression. Result. Tuberculosis incidence among the Isoniazid treated group was 1.98 per 100 person-years and 4.52 per 100 person-years in the untreated group. CD4 cell count, clinical staging, body mass index (BMI), not using cotrimoxazole, body weight, and functional status were significant predictors of tuberculosis risk. Isoniazid preventive therapy use was associated with 55% reduction of tuberculosis incidence. Conclusion. Isoniazid preventive therapy use was associated with significant reduction in tuberculosis incidence, even in the absence of Tuberculin Skin Test (TST). Therefore, isoniazid preventive therapy (IPT) coverage should be used more widely, with special emphasis given to patients at higher risk of tuberculosis. The study shows that the absence of TST testing should not be a limitation.

Incidence and predictors of extrapulmonary tuberculosis among people living with Human Immunodeficiency Virus in Addis Ababa, Ethiopia: A retrospective cohort study

“…We observed that the risk to develop EPTB is higher when they are underweight at the baseline, compared to those with normal weight (CHR = 2.227, 95%CI = 1.399-3.544). Similar findings were reported from other studies [6,7,23], where nutritional status is a key factor development of TB.…”

“…This might be because HIV positive patients who were on ambulatory or bedridden functional status at baseline might have low CD4 counts that could make them more susceptible to co-infections like tuberculosis. Previous studies also supported this [2,3,7,13,22,23]. We observed that the risk to develop EPTB is higher when they are underweight at the baseline, compared to those with normal weight (CHR = 2.227, 95%CI = 1.399-3.544).…”

“…Immune status is a key factor for the susceptibility of a host for TB, such that when the immune system becomes week the likely hood to be infected with TB increases [6] [24]. Based on this study and findings from previous studies done in Ethiopia and other countries, individuals who had lower CD4 count at the time of enrollment had higher risk to develop TB [2,6,14,20,21,23,[26][27][28][29][30][31][32][33]. The other independent predictor of EPTB observed in this study was the baseline hemoglobin value.…”

“…This study revealed that those PLHIV who were in advanced WHO stages III or IV at the time of enrollment had 2.72 times the risk to develop EPTB at any time compared to those who were on WHO stage I or II. Similarly, different studies reported TB was more common in advanced HIV stages [2,3,6,7,13,14,20,[22][23][24][25][26][27][28][29].…”

Absolute risk of tuberculosis among untreated populations with a positive tuberculin skin test or interferon-gamma release assay result: systematic review and meta-analysis

“…This difference could be attributable to healthcare system strengthening31 or differences in the study populations included in each period. This difference might also reflect the expanded use of antiretroviral treatment, which increased from a range of 0-61% in pre-2006 studies to 40-71% in studies initiated from 2006 onwards 32. Among people requiring dialysis or undergoing transplantation, observed rates of disease were variable; estimates for incidence rate ratios were, however, consistently low.…”