Cavity Volume and Proximity to Airway May Affect Tuberculosis Treatment

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Individuals with tuberculosis who had large cavity volumes closer to the airway had a cough frequency 2-fold higher than in individuals with smaller cavities.
Individuals with tuberculosis who had large cavity volumes closer to the airway had a cough frequency 2-fold higher than in individuals with smaller cavities.

Individuals diagnosed with tuberculosis with large cavitary lung disease may have a greater cough frequency that lasts for a longer period of time, especially when cavities are closer to the airway, according to a study published in CHEST.

Researchers identified 41 HIV-negative individuals at 2 tertiary hospitals in Peru who were diagnosed with culture-confirmed, drug-susceptible pulmonary tuberculosis  and conducted a longitudinal prospective study to identify an association between cough frequency and duration, as well as radiological characteristics (cavity volume and cavity proximity to the airway). In addition, researchers assessed an association between radiological characteristics and bacillary burden and culture conversion.

Individuals with large cavity volumes had a cough frequency 2-fold higher than those individuals with smaller cavities (rate ratio [RR], 1.98; 95% CI, 1.17-3.35; P =.01). In addition, individuals with cavities farther away from the airway had a significantly lower cough frequency compared with those with cavities closer to the airway (RR, 0.41; 95% CI, 0.248-0.68; P =.001). When cavity volume and proximity to the airway combined were analyzed during treatment, only proximity to the airway was significant (RR, 0.38; 95% CI, 0.20-0.72; P =.003). During treatment, older age had a stronger trend for cough frequency, and both atelectasis and pleural effusion were associated with a higher cough frequency (RR, 1.89 [95% CI, 1.17-3.08; P =.01] and RR, 1.99 [95% CI, 1.06-3.73; P =.03], respectively).

During treatment, a higher bacillary burden and faster culture growth were associated with larger cavity volumes (mean difference [MD], −2.42; 95% CI, −4.6 to −0.28; P =.03), whereas lower bacillary burden and longer time for culture growth was associated with cavities farther from the airway (MD, 3.26; 95% CI, 1.35-5.2; P =.001). Only proximity to the airway remained statistically significant during treatment when analyzing both cavity volume and proximity (MD, 2.76; 95% CI, 1.01-4.5; P =.002).

Despite being observed to have a cough cessation rate 3 times faster in individuals with smaller cavities compared with larger cavities, the results were not found to be statistically significant (adjusted hazard ratio, 2.89; 95% CI, 0.95-8.8; P =.06). Interestingly, cavities located >10 mm from the airway had a 3 times higher hazard for coughing cessation compared with cavities ≤10 mm (adjusted HR, 3.61; 95% CI, 1.26-10.4; P =.02), with probabilities of 37.3% and 75.0% for those closer and farther from the airway, respectively. Probabilities of culture conversion were 100% and 73.3% for small and large cavities, respectively.

The researchers concluded that there is an association between cough frequency during treatment with both cavitary volume and proximity to the airway. Therefore, because a patient with a large cavity close to the airway is at an increased risk of coughing during treatment, clinicians can identify this individual as being at a higher risk for expelling more Mycobacterium tuberculosis  into the environment, and should closely monitor them during treatment.

Reference

Proaño A, Bui D, López J, et al; for the Tuberculosis Working Group in Peru. Cough frequency during treatment associated with baseline cavitary volume and proximity to the airway in pulmonary tuberculosis [published online March 17, 2018]. CHEST. doi:10.1016/j.chest.2018.03.006

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