Incidence and risk factors for tuberculosis at a rural HIV clinic in Uganda, 2012-2019; A retrospective cohort study

Tuberculosis (TB) is the leading cause of death among people living with HIV (PLHIV). Antiretroviral therapy (ART) initiation lowers the risk of HIV-associated TB. Earlier studies have shown TB incidence to be high in the first year of ART. We undertook a study to (1) assess the incidence of TB and (2) associated factors among persons initiating ART in a rural cohort.

We conducted a retrospective cohort analysis study among PLHIV aged ≥ 18 years, initiated on ART from January 1, 2012, to December 31, 2019, and TB disease-free at the time of ART initiation, at Kalisizo ART clinic. TB disease incidence was calculated by dividing the number of new TB cases by the total follow-up time expressed per 100 person-years among persons followed up until the date of incident TB disease, loss to follow-up, transfer out, death or censored at the end of the study; whichever occurred first. Factors associated with TB disease incidence were assessed in the multivariable analysis by Poisson regression analysis at 5% significance level.

For the period 2012 to 2019, 2,589 PLHIV were initiated on ART; 57% (1,470/2,589) were female. Females were more likely to be aged below 35 years while males were more likely to be aged 25-44 years (p < 0.001). Eighty-seven per cent (1,269/1,470) of females compared to 78% (866/1,119) of males were in WHO clinical stage 1 (p < 0.001). Sixty-one TB disease events were observed in 7,363 person-years. The overall TB disease incidence was 0.83 (95% CI: 0.63-1.06) per 100 person-years. Males were more likely than females to develop TB disease, adjusted incidence rate ratio (adj IRR) 2.13 (95% CI: 1.27-3.57) per 100 person-years, p = 0.004. Compared to using ART for 0-5 months, time on ART was associated with a lower TB incidence rate at 6-12 months, 13-24 months, > 24 months (adj IRR 0.20 (95% CI: 0.09-0.46), 0.14 (95% CI: 0.06-0.33), 0.16 (95% CI: 0.08-0.31) p < 0.001 respectively).

Incidence of TB among PLHIV on ART was low in this rural population. Clinicians offering care to people with HIV in the rural setting should have a heightened index of suspicion for TB disease.