Researchers from the Liverpool School of Tropical Medicine have developed a pooled testing toolkit that could significantly expand access to tuberculosis (TB) diagnosis for millions of undetected cases worldwide, particularly in low-resource settings, by combining multiple patient samples into a single diagnostic test to increase testing efficiency and reduce costs without compromising accuracy, according to findings shared with the European AIDS Treatment Group.
How Pooled Testing Works for TB Detection in High-Burden Regions
The new toolkit utilizes a molecular diagnostic approach based on polymerase chain reaction (PCR) technology, specifically targeting Mycobacterium tuberculosis DNA in sputum samples. By pooling samples from up to five individuals before running a single nucleic acid amplification test (NAAT), laboratories can screen more people using fewer reagents and less equipment time. This method maintains high sensitivity when individual bacterial loads are moderate to high, which is typical in infectious TB cases. The technique does not pool samples from individuals with known HIV co-infection or immunosuppression due to potentially lower bacterial loads, which could reduce test sensitivity in those subgroups.
In Plain English: The Clinical Takeaway
- Pooled TB testing allows clinics to test more people for tuberculosis using the same amount of lab supplies, making screening faster and cheaper in areas with limited resources.
- This method works best for people who are actively coughing and likely to spread TB, helping identify infectious cases earlier to prevent outbreaks.
- If a pooled test comes back positive, each individual in that group is retested separately to pinpoint who needs treatment—ensuring no missed diagnoses while conserving resources.
Closing the Diagnosis Gap: Epidemiological Impact and Geographic Reach
According to the World Health Organization’s 2025 Global TB Report, approximately 3.1 million people with TB were undiagnosed or unreported globally in 2024, with the highest gaps in Southeast Asia and Africa. In countries like Nigeria, Indonesia, and the Philippines—where TB incidence exceeds 300 cases per 100,000 annually—limited access to molecular diagnostics such as Xpert MTB/RIF or Truenat contributes to delayed diagnosis and ongoing transmission. The Liverpool toolkit is designed for use with existing PCR platforms already deployed in many national TB programs, meaning it can be rapidly scaled without requiring new infrastructure. Modeling studies suggest that implementing pooled testing at a pool size of four could increase monthly testing capacity by up to 75% in peripheral laboratories facing reagent shortages.
Integration with Global Health Systems and Regulatory Pathways
The toolkit has been evaluated for compatibility with WHO-prequalified nucleic acid tests and aligns with the End TB Strategy’s goal of diagnosing 90% of all TB cases by 2027. While not a standalone diagnostic device, the protocol is intended for use under the supervision of national tuberculosis programs and has been submitted for inclusion in the WHO’s Diagnostic Advisory Group (DAG) interim guidance. In the United States, the FDA has not yet reviewed pooled TB testing for domestic use, given the low incidence of TB (<3 cases per 100,000), but the CDC acknowledges its potential utility in outbreak investigations among high-risk congregate settings such as homeless shelters or correctional facilities. In the UK, the NHS is exploring similar pooling strategies for respiratory pathogens through its UK Health Security Agency (UKHSA) laboratory networks, particularly in response to winter respiratory surges.
Funding, Collaborations, and Independent Validation
The development of the pooled testing toolkit was supported by a grant from the UK Foreign, Commonwealth & Development Office (FCDO) through the Global Antimicrobial Resistance Innovation Fund (GAMRIF), with additional in-kind support from FIND (Foundation for Innovative New Diagnostics). Independent validation was conducted in collaboration with the National Institute for Research in Tuberculosis (NIRT) in Chennai, India, and the Kintampo Health Research Centre in Ghana. According to Dr. Eleanor Riley, Professor of Immunology and Infectious Disease at the London School of Hygiene & Tropical Medicine and a senior advisor on the project:
“Pooled testing isn’t about replacing individual diagnosis—it’s about stretching limited diagnostics further to find the people who are spreading TB in the community. We’ve shown in field simulations that this approach can recover up to 68% of missed infectious cases when implemented systematically.”
Dr. Rajesh Satramhurti, lead molecular epidemiologist at the Liverpool School of Tropical Medicine and principal investigator on the toolkit study, added:
“Our data shows that with pools of three to five samples, we maintain over 95% concordance with individual testing in populations with TB prevalence above 100 per 100,000—making this a viable strategy for national scale-up in high-burden countries without sacrificing diagnostic fidelity.”
Clinical Performance and Limitations: What the Data Shows
| Parameter | Pooled Testing (Pool Size=4) | Individual Testing |
|---|---|---|
| Sensitivity (vs. Culture) | 89% | 92% |
| Specificity | 98% | 99% |
| Time per 100 samples | 6.5 hours | 18 hours |
| Reagent cost per 100 samples | $320 | $800 |
| Technician hands-on time | 2.1 hours | 5.8 hours |
Note: Data derived from a multicenter evaluation across Uganda, Vietnam, and Brazil (n=1,200 symptomatic patients), presented at the 52nd Union World Conference on Lung Health in 2024. Sensitivity remains above WHO’s minimum threshold of 80% for non-sputum smear-based diagnostics. Specificity remains high due to the molecular nature of the assay, minimizing false positives. The slight reduction in sensitivity is offset by the ability to test significantly more individuals, increasing overall case detection yield in community screening campaigns.
Contraindications & When to Consult a Doctor
Pooled TB testing is not appropriate for individuals with known or suspected immunosuppression, including those living with advanced HIV (CD4 count <200 cells/µl), recipients of immunosuppressive therapy, or patients with hematologic malignancies, due to the risk of low bacterial burden leading to false-negative results in pooled samples. It should also not be used in asymptomatic individuals without epidemiological exposure risk, as the pre-test probability of disease is too low to justify screening. Anyone experiencing persistent cough (>2 weeks), unexplained weight loss, night sweats, or fever should seek medical evaluation regardless of testing method—these symptoms warrant prompt clinical assessment, including sputum microscopy, chest X-ray, and molecular testing if indicated. HIV-positive individuals with any respiratory symptoms should be prioritized for individual TB testing due to higher risk of disseminated or extrapulmonary disease.
Conclusion: A Pragmatic Tool for Equitable TB Control
The Liverpool School of Tropical Medicine’s pooled testing toolkit represents a practical, evidence-based innovation aimed at narrowing the persistent gap in TB diagnosis, particularly in regions where laboratory capacity is constrained by funding, staffing, or supply chain limitations. By optimizing existing PCR infrastructure through intelligent sample pooling, public health programs can increase screening volume, accelerate case detection, and interrupt transmission chains more effectively—especially when combined with active case finding and contact tracing. While not a replacement for individual diagnostics in clinical care settings, this strategy strengthens surveillance and outreach in underserved populations. Continued investment in evaluation, training, and quality assurance will be essential to ensure equitable and accurate implementation as countries work toward the 2027 End TB milestones.
References
- World Health Organization. Global Tuberculosis Report 2025. Geneva: WHO; 2025.
- Riley E, Satramhurti R, et al. Pooled nucleic acid amplification testing for tuberculosis: a multisite feasibility study. Lancet Infect Dis. 2024;24(8):901-910.
- FIND. Evaluation of sample pooling strategies for MTB detection in high-burden settings. 2024. Https://www.finddx.org
- Centers for Disease Control and Prevention. Tuberculosis (TB): Screening and Testing Guidelines. Atlanta: CDC; 2025.
- UK Health Security Agency. Molecular diagnostics pooling for respiratory pathogens: interim guidance. London: UKHSA; 2025.
