Pooling Sputum to Speed TB Tests in Havana

Tuberculosis remains a public health challenge even in places with strong control programs. In Cuba, the National Tuberculosis Control and Elimination Program (PNCET, acronym in Spanish) adopted molecular testing in 2014, using Xpert® MTB/RIF (Cepheid, Sunnyvale, CA, USA) to speed diagnosis. But financial limits and difficult access to kits and cartridges of U.S. origin mean the test is reserved for prioritized, vulnerable groups. As a result only about one third of cases reported each year are first diagnosed by rapid tests. To reach more people sooner, Raúl Díaz-Rodríguez and colleagues are testing a combination of approaches: pooling sputum samples from several people into a single Xpert® MTB/RIF Ultra cartridge, and helping people produce sputum using a positive expiratory pressure (PEP) device, the Lung Flute (LF) ECO (Acoustic Innovation, Tokyo, Japan). Pooling has been used with samples from symptomatic respiratory patients in high-burden countries, and inducing sputum can help people who do not expectorate spontaneously — including those with incipient or asymptomatic disease and many children. The study focuses on household contacts of bacteriologically confirmed pulmonary TB cases, seeking ways to find infections earlier and more affordably.

The study tests two practical methods together. First, it will evaluate the pooled sputum method: several sputum specimens from different household contacts are combined and applied in a single Xpert® MTB/RIF Ultra cartridge to run a rapid molecular assay. Xpert® MTB/RIF and Xpert® MTB/RIF Ultra are the molecular tools at the center of the plan; the original Xpert® MTB/RIF test is in current use in Cuba. Second, the team will estimate how many household contacts can produce a sample suitable for Xpert® MTB/RIF Ultra when guided to use the Lung Flute (LF) ECO PEP device. The project notes that pooled testing has already been applied to symptomatic respiratory patients in high-burden settings and that sputum induced by the LF ECO can give results similar to using a hypertonic solution. Because kits and cartridges are costly and of limited availability, assessing pooled testing together with a sputum-induction device aims to increase the number of people who can be screened rapidly without consuming a cartridge per person.

If the pooled sputum approach and the Lung Flute ECO device work as intended, the implications could be substantial for TB control. Pooling samples into a single Xpert® MTB/RIF Ultra cartridge would raise the reach of rapid molecular diagnosis, reducing the number of cartridges needed and lowering per-person testing costs. That could let programs test more household contacts — including those who are early in the course of disease or who cannot expectorate spontaneously, such as many children — and detect infectious cases earlier, cutting transmission in the community. For Latin America and other regions with limited budgets and constrained access to imported consumables, a validated pooling strategy offers a potentially sustainable way to expand testing without relying on preferential pricing or special trade conditions. The study aims to produce practical evidence that national programs can use to scale up testing, reduce sources of infection, and support the broader goal of TB elimination by finding cases more efficiently.