A large campaign in Uganda to ramp up HIV testing and immediate HIV treatment reduced the incidence of tuberculosis in the intervention communities by 27% after one year, underlining the potential impact of HIV-related investments on wider population health, investigators of the SEARCH study reported at AIDS 2022 on Sunday.

The SEARCH study is one of the largest implementation studies of universal HIV test-and-treat to be conducted. The study randomised communities to receive either the intervention or standard of care according to national guidelines and took place between 2013 and 2016 in rural communities in Uganda and Kenya. The intervention consisted of:

  • A multi-disease prevention campaign that included testing for HIV, diabetes and hypertension, with a two-week health fair and household testing in each community.
  • Linkage to care of anyone who tested positive
  • Immediate antiretroviral therapy (ART), regardless of CD4 count

Results from the SEARCH study have been presented at several major conferences and demonstrate substantial impact of the intervention, including:

Glossary

active TB

Active disease caused by Mycobacterium tuberculosis, as evidenced by a confirmatory culture, or, in the absence of culture, suggestive clinical symptoms.

linkage to care

Refers to an individual’s entry into specialist HIV care after being diagnosed with HIV. 

p-value

The result of a statistical test which tells us whether the results of a study are likely to be due to chance and would not be confirmed if the study was repeated. All p-values are between 0 and 1; the most reliable studies have p-values very close to 0. A p-value of 0.001 means that there is a 1 in 1000 probability that the results are due to chance and do not reflect a real difference. A p-value of 0.05 means there is a 1 in 20 probability that the results are due to chance. When a p-value is 0.05 or below, the result is considered to be ‘statistically significant’. Confidence intervals give similar information to p-values but are easier to interpret. 

test and treat

A public health strategy in which widespread HIV testing is facilitated and immediate treatment for those diagnosed with HIV is encouraged.

standard of care

Treatment that experts agree is appropriate, accepted, and widely used for a given disease or condition. In a clinical trial, one group may receive the experimental intervention and another group may receive the standard of care.

At AIDS 2022, Dr Carina Marquez of the University of California San Francisco presented results of an analysis of TB incidence in nine communities that participated in the SEARCH study in Uganda, where TB symptom screening was a component of the intervention.

The study sampled 100 households that included at least one person with HIV and 100 households without a person with HIV in each community. Tuberculin skin tests were carried out on each household member over the age of 5 at baseline and one year later.

The study measured the incidence of TB after one year by looking at conversion from negative to positive tuberculin skin test, indicating likely recent exposure to TB in the community.

The study sampled 1435 households in nine communities, testing 4,884 people at baseline (58% of those eligible to participate). Those tested were predominantly under 18 (58% in the intervention communities), 46% lived in a household with a person with HIV, 10% were living with HIV and over 90% had received the BCG vaccination to protect against TB.

Twenty-two percent tested positive at baseline, leaving 3,381 people in the TST-negative cohort at baseline. One year later, 78% of the TST-negative cohort were available for re-testing.

After one year, the incidence of TB was 27% lower in intervention communities. Sixteen percent of participants in intervention communities tested positive for TB after one year compared to 22% in control group communities. The reduction in risk was significant in children aged 5-11 years (aRR 0.71, 95% CI 0.52-0.97, p=0.016) but not in participants aged 12 and over (aRR 0.84, 95% CI 0.64-1.11, p=0.106). This result is probably explained by the fact that adolescents and adults were more likely to have been exposed to TB previously, Carina Marquez said.

She told the conference that reduced TB incidence is likely to be a consequence of several factors. As well as a reduction in the duration of infectiousness due to improved detection and treatment of active TB through symptom screening, susceptibility to the activation of latent TB or progression to active TB is likely to be reduced due to improved immune status in people on antiretroviral treatment. This leads to a reduction in the number of people with active TB in the community.

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