Pooled Sputum Testing Offers Lower-Cost Molecular Diagnosis for Tuberculosis

Tuberculosis remains a major diagnostic challenge, with many cases going undetected and untreated. Limited access to rapid molecular diagnostic tests can delay diagnosis and allow transmission to continue in homes and communities. Global TB control is further constrained by chronic underinvestment and inequitable testing access. Against this backdrop, researchers now present evidence that pooled sputum testing could expand access to rapid, lower-cost TB diagnosis.

Liverpool School of Tropical Medicine (LSTM) led the Start4All study, a four-year Unitaid-funded partnership with the Stop TB Partnership and research partners in seven high TB-burden countries. The study evaluated pooled sputum testing for tuberculosis using Cepheid's Xpert MTB/RIF Ultra. The method examines sputum specimens from several people in a single molecular test cartridge, with each person’s sample also tested individually.

Image: The study was carried out by Start4All, a partnership led by Liverpool School of Tropical Medicine (LSTM) with the Stop TB Partnership and research partners in seven countries with a high TB burden (Photo courtesy of Liverpool School of Tropical Medicine)

Between November 2023 and February 2025, more than 14,000 people with symptoms of TB participated in Bangladesh, Brazil, Cameroon, Kenya, Malawi, Nigeria, and Vietnam. Screening took place in communities, primary health centers, and district hospitals. Each sputum specimen was tested alone and again as part of a pool of up to four specimens. The study was described as the first to measure pooled testing against culture, the reference standard for TB diagnosis, rather than only against individual molecular testing.

Pooled testing used just over 7,000 cartridges instead of roughly 14,000 required for individual testing, representing a 51% reduction. The cost of each test fell from nearly USD 8 to less than USD 4. Sensitivity was 3.1% lower than individual testing, mainly in specimens with very low TB bacterial load. The findings were published in The Lancet Global Health on September 24, 2026, and directly informed World Health Organization guidelines on pooled testing issued earlier this year.

The work is part of a series of Start4All outputs on pooled testing, including publications in The Lancet Respiratory Medicine, BMJ Open, and Clinical Microbiology and Infection. The source also states that a toolkit, a test cost calculator, and a decision tool have been developed for healthcare professionals and National TB Programmes. In the next phase of Start4All, pooled testing will be combined with computer-aided chest X-ray triage and expanded to tongue swab specimens.

“This is the evidence that took pooled testing from a promising idea to a WHO recommendation, and it comes from routine laboratories and clinics in the countries that need it most, not from a research setting. Pooling needs no new technology. It makes smarter use of the machines and cartridges laboratories already have, so that many more people can receive a rapid molecular test from the same budget. That is what reaching the missed millions looks like in practice,” said Dr. Tom Wingfield, deputy director of LSTM’s Centre for Tuberculosis Research and chief investigator on Start4All.

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