Annual community screening finds undiagnosed TB, especially in men

Tuberculosis remains a major public health challenge in parts of southern Africa, and the World Health Organization suggests systematic screening may be useful in places where TB prevalence is above 0.5%, though evidence has been limited. To test how well community-wide screening works in real life, researchers running the HPTN 071 (PopART) cluster-randomized trial carried out universal HIV and TB testing across 21 communities in Zambia and South Africa from January 2014 to December 2017. The study areas had estimated TB prevalence of about 0.5% in Zambia and 1.6% in South Africa. Under the PopART approach, trained community health workers made annual household visits to offer HIV testing and to ask residents about TB symptoms, collecting sputum from anyone who screened positive and helping people get linked to treatment. Thomas Gachie is the corresponding author for the report on these activities. The trial aimed to see how many previously undiagnosed TB cases this systematic, repeated screening would uncover, and whether yields changed over multiple annual rounds of visits.

The PopART teams analysed TB screening and diagnosis data across three rounds (R1–R3) in Zambia and for the third round (R3) in South Africa where complete data were available. During household visits, sputum samples from symptom-positive people were tested using Xpert-MTB/RIF or smear microscopy, and efforts were made to link diagnosed people to treatment. In Zambia the yield of newly diagnosed TB per 100,000 people rose across rounds: R1 = 81, R2 = 93, R3 = 110, with a statistically significant trend (p = 0.003). In R3 South Africa the yield was higher at 380 per 100,000. In R3, yields were higher in men (Zambia: 146; South Africa: 543) than women (Zambia: 76; South Africa: 257). Yields were also highest among people who were newly diagnosed HIV-positive (Zambia: 541; South Africa: 789) compared with HIV-negative people (Zambia: 48; South Africa: 170) and people who self-reported as HIV-positive and on ART (Zambia: 105; South Africa: 192). In Zambia R3, participants who had been screened twice before had 38% lower odds of being diagnosed with TB than those screened for the first time (adjusted odds ratio = 0.62, 95% CI 0.43–0.90).

Taken together, these results show that systematic symptom screening delivered by community health workers can identify previously undiagnosed TB cases, particularly among men and among people who are newly diagnosed with HIV. The higher yields in South Africa and among certain subgroups suggest that the same screening approach finds different numbers of cases depending on local prevalence and population groups reached. At the same time, investigators noted that the number of cases found through these annual symptom checks was relatively low compared to the estimated overall TB prevalence in the study areas, indicating that symptom-based, door-to-door screening may miss many people with TB or that repeated rounds find fewer new cases over time. These findings come from the HPTN 071 (PopART) intervention and are reported under trial registration NCT01900977, offering practical information for programs considering community-based TB and HIV screening.