Portable lab-in-tube TB screening device yields results in under an hour

A handheld, battery-powered lab-in-tube (LIT) assay device can deliver accurate tuberculosis (TB) diagnoses in less than an hour, according to a study.

Developed by researchers from Tulane University in New Orleans, Louisiana, US, the LIT assay integrates sputum or saliva specimen liquification, Mycobacterium tuberculosis bacilli lysis, recombinase polymerase amplification (RPA), and CRISPR detection steps into a single consumable tube.

The tube is then processed and analysed by the portable device. This device is a 3D-printed case fitted with a rechargeable battery, a miniature incubator, imaging components, a 3.5-in touchscreen, and a Raspberry Pi microprocessor.

The LIT assay device was designed to detect M. tuberculosis DNA in patient serum, saliva, and sputum samples with a sample-to-answer time of <1 h and that could be deployed as a point-of-care TB test for multiple TB manifestations, the researchers said.

Paediatric blood samples

The researchers tested the device using blood samples from 27 children with either pulmonary or extrapulmonary TB. Results showed a sensitivity of 81 percent for detecting TB, 83 percent for pulmonary TB, and 75 percent for extrapulmonary TB. This performance exceeded that of sputum/gastric lavage cultures (55 percent) and GeneXpert MTB/RIF (68 percent), meeting the WHO target product profile criteria for new nonsputum TB diagnostics. [Sci Transl Med 2025;doi:10.1126/scitranslmed.adp6411]

“Serum LIT assay results were positive for 78 percent of extrapulmonary or pulmonary plus extrapulmonary TB cases, which otherwise required tissue biopsy, X-ray imagery, or other clinical observations to diagnose,” according to the researchers.

When the test was conducted using first blood samples from 35 children who were close contacts but did not demonstrate evidence of infection and were negative on tuberculin skin test, the LIT assay had a specificity of 94 percent. In another cohort of 49 children who had low likelihood of TB disease but who were not tested for TB, all tested negative on the LIT assay.

Given that sputum is the primary diagnostic specimen for pulmonary TB diagnosis, these results hold clinical importance for “young children, individuals living with HIV or other immune insufficiencies, and individuals with extrapulmonary TB [who] often cannot produce sputum or produce sputum with low M. tuberculosis concentrations that yield false negative results,” the researchers said.

“Changes in assay results for [samples] isolated during treatment were also highly predictive of clinical response,” underscoring the potential value of the LIT assay for monitoring treatment effectiveness in children, they added.

Adult saliva, sputum samples

The researchers also evaluated the diagnostic performance of the LIT assay device using saliva samples from a case-control cohort of 15 adults with TB disease and 15 who lacked evidence of infection. Results showed a 73-percent sensitivity and 100-percent specificity, although fluorescent signals from the TB-positive samples varied widely.

For sputum samples obtained from 36 adults with suspected TB, the LIT assay had a diagnostic sensitivity of 100 percent and specificity of 90.3 percent. Specificity was similar for samples obtained from individuals with nontuberculous mycobacteria infections (87.5 percent) and those with no evidence of infection (91.3 percent).

Low-cost advantage

“Our results indicate that [the LIT assay] can detect adult and paediatric TB, including pulmonary and extrapulmonary TB cases, with high sensitivity and specificity when using serum, saliva, or sputum as the diagnostic specimen, suggesting that this approach has strong potential as a point-of-care test for TB diagnosis in resource-limited settings underserved by current methods,” the researchers said.

Importantly, the LIT assay device offers a cheaper TB testing alternative. Each device costs less than USD 800, and the cost per test is extremely low at around USD 2.7. In contrast, the GeneXpert system—aside from being larger and requiring extensive technology and logistics—costs a minimum of USD 19,000 per machine and approximately USD 8 per test. The researchers emphasized that this low-cost feature of the LIT assay is crucial for use in resource-limited settings underserved by current methods.

Lead researcher Brady Youngquist, a graduate student in the Tulane University Center for Cellular and Molecular Diagnostics, added that the LIT assay device “reduces the expertise and equipment required for TB diagnosis which is essential for point-of-care application.”

“Saliva-based testing for TB is particularly exciting because it can be easily obtained in all patients and can be used for portable testing without the need for blood draw. And sputum is often not produced in children and patients living with HIV, a common co-infection,” Youngquist said.