Aerosol Sampling Detects TB DNA in Primary Care Patients

A recent study published in Open Forum Infectious Diseases investigates a novel, non‑sputum approach to tuberculosis (TB) diagnosis and transmission surveillance by collecting aerosolized Mycobacterium tuberculosis DNA (termed AMD) from people under evaluation for pulmonary TB in primary care in South Africa.

Diagnosing TB using sputum-based testing has long been standard, but it is limited in patients who cannot produce sputum and offers little direct insight into infectiousness. The authors recruited 137 symptomatic adults who had already undergone sputum testing with Xpert MTB/RIF Ultra (“Ultra”) and used a portable electrostatic aerosol sampler (the THOR device) at clinic sites to capture cough aerosols on site. These aerosol samples were then analyzed by Ultra to detect Mtb DNA.

Compared to sputum Ultra, aerosol AMD detection had a sensitivity of 46.6 % (95 % CI 42.5 – 50.7) and specificity of 76.5 % (95 % CI 70.4 – 82.5). In participants whose sputum Ultra result was in the “high” semi‑quantitative category, sensitivity rose to 56.9 %. The study identified male sex combined with medium or higher sputum Ultra quantitation as being independently associated with AMD detection (adjusted relative risk 3.26). A reported symptom of fever trended toward a negative association (adjusted RR 0.58; p = 0.099).

Interestingly, in three participants, the ratio of sputum to aerosol Mtb DNA was ≥ 0.75, suggesting these individuals had a strong capacity to emit Mtb DNA in exhaled aerosols. The researchers also detected AMD in 30 % of environmental control samples despite rigorous decontamination procedures—underscoring both the sensitivity of the sampling device and the risk of environmental contamination or nosocomial transmission.

The authors conclude that electrostatic aerosol sampling is feasible in primary care settings and may help identify patients with active transmission potential. They suggest that if refined, such methods could complement existing diagnostics to better characterize who is most likely to spread TB—and potentially help guide public health interventions.

While promising, the approach faces key challenges. The modest sensitivity means many true TB cases would be missed if aerosol sampling were used alone. Environmental contamination remains a concern, as evidenced by positive results in control samples despite careful protocols. The relationship between AMD detection and actual infectivity (i.e. viable bacilli, not just DNA fragments) also needs clearer elucidation. Finally, for implementation in high-burden settings, considerations of cost, device portability, and integration into clinical workflows will be critical.

This work takes an important step toward bridging diagnosis and transmission assessment in TB. If future studies validate the correlation between aerosol DNA detection and actual infectiousness, aerosol sampling might someday become a tool not just for diagnosing disease, but for interrupting its spread.