Tongue swabs help find TB in people living with HIV

Tuberculosis (TB) remains a major health threat for people living with HIV (PWH), and many cases are missed because people do not always provide sputum samples or seek care specifically for TB. Gerard A. Cangelosi and colleagues tested a Targeted Universal Tuberculosis Testing (TUTT) idea: routinely testing high-risk people, even when they were not seeking TB care. The team enrolled 251 PWH in KwaZulu-Natal, South Africa, most of whom were coming to primary healthcare clinics to start antiretroviral therapy. Participants had a median age of 34 years, were 56% female, and 67% reported TB symptoms. Median CD4 count was 347 cells/µl and 16% had a prior history of TB. To make testing easier and less invasive, researchers tried tongue swabs (TS) collected with Copan FLOQSwab and Medline foam swab, alongside traditional samples like urine and sputum. The study asked whether non-sputum methods could pick up TB cases when people are tested regardless of symptoms, and whether tongue swabs could work as part of TUTT programs for this vulnerable group.

The study compared two tongue swab testing protocols and standard reference tests. FLOQSwabs were tested by sequence-specific magnetic capture (SSMaC) with qPCR (FLOQSwab-SSMaC). Medline foam swabs were processed by centrifuge-sedimentation and high-volume qPCR (foam-sedimentation). Urine lipoarabinomannan was detected using LF-LAM. The extended microbiological reference standard (eMRS) was any positive result on Xpert Ultra and/or liquid culture of sputum. Against that eMRS, FLOQSwab-SSMaC detected 43% of cases (13/30) and was 100% specific (131/131). Foam-sedimentation detected 47% (9/29) and was 100% specific (176/176). When sputum Xpert Ultra Trace-positive results were excluded from the eMRS, sensitivities rose to 52% for FLOQSwab-SSMaC and 50% for foam-sedimentation. Tongue swab testing was more sensitive than urine LF-LAM, and both tongue swabs and urine were more sensitive in participants with CD4 counts below 200 cells/µl.

These results show that tongue swab testing, combined with molecular methods, can detect about half of TB cases among PWH and does so with high specificity. That level of sensitivity means tongue swabs are not a complete replacement for sputum testing, but they offer a practical, non-invasive option where sputum collection is difficult or not possible. Because tongue swabs outperformed urine LF-LAM in this study population and worked better in people with lower CD4 counts, they could be especially useful in targeted programs for PWH, including those newly entering care or unable to produce sputum. The study suggests TUTT programs that include tongue swabs and reliable molecular tests may help find undiagnosed TB earlier, reduce transmission, and link more people to treatment—particularly in resource-limited settings and primary health clinics where traditional sputum-based testing is a barrier.