PHILADELPHIA, PAThe use of isoniazid as preventive therapy among HIV-infected patients receiving highly active antiretroviral therapy (HAART) is associated with significantly lower tuberculosis incidence, reported Bethel Shiferaw, MD, MPH, from Nassau University Medical Center, East Meadow, at IDWeek 2014.

Tuberculosis is the top cause of HIV-related morbidity and mortality across the world. Isoniazid preventive therapy is not broadly used although it has been shown to reduce tuberculosis incidence. 

Shiferaw and team set out to compare the risk of tuberculosis development among HAART receiving HIV-infected patients who took isoniazid preventive therapy compared to those who did not take isoniazid preventive therapy.

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They conducted a secondary analysis of medical records of patients receiving HAART from 2009 to 2012 in East Africa (n=836). Primary exposure of interest was time-fixed isoniazid preventive therapy, and the primary outcome of interest was incidence of tuberculosis. After excluding active tuberculosis, the HIV-infected patients were given oral isoniazid therapy for 6 months.

Results showed that the cumulative incidence of tuberculosis was 5.7/100 person-years.  Patients who received isoniazid preventive therapy had a decreased incidence by 85% (hazard ratio [HR] 0.15; 95% CI: 0.07-0.32) compared to those who had not received isoniazid. Women were also found to develop tuberculosis less likely than men (HR 0.64; 95% CI: 0.45-7.5).

Patients with WHO Stage 2 (HR 1.8, 95% CI; 0.45-7.15), Stage 3 (HR 7.2; 95% CI: 2.18-23.46), and Stage 4 (HR 31.1; 95% CI: 9.25-104.57) had higher risk for developing tuberculosis compared to patients with baseline Stage 1. A multivariate Cox proportional hazard analysis (including isoniazid preventive therapy, age, sex, WHO stage, and CD4 count) showed an overall 78% reduction in risk of tuberculosis in patients who took isoniazid preventive therapy (HR 0.22; 95% CI: 0.10-0.48).

Isoniazid as preventive therapy in HIV-positive patients receiving HAART resulted in significantly reduced tuberculosis incidence. Shiferaw added that countries with a high tuberculosis burden should “give a high priority in the scaling up of isoniazid preventive therapy to improve tuberculosis control.” 

This article originally appeared on MPR