Feno levels may predict complications among patients with nontuberculous mycobacterial pulmonary disease: Study

Measurement of exhaled nitric oxide (FeNO) is a potentially useful diagnostic test for asthma. However, no study has explored the relationship between FeNO and respiratory symptoms of nontuberculous mycobacterial pulmonary disease (NTM-PD) complicated with asthma. The objective of this study was to assess the utility of measuring FeNO levels in patients with nontuberculous mycobacterial pulmonary disease complicated by asthma. In this single-center retrospective cohort study, 140 nontuberculous mycobacterial pulmonary disease patients with FeNO measured were enrolled. They selected nontuberculous mycobacteria-PD patients who complicated with asthma as the nontuberculous mycobacteria+BA group, defined using the following criteria: nontuberculous mycobacteria patients with symptoms consistent with asthma, and nontuberculous mycobacteria patients with symptomatic improvement after diagnostic therapy with ICS ± a long-acting beta 2-agonist (LABA). We then calculated a diagnostic cutoff point to distinguish between the NTM+BA groups and the nontuberculous mycobacteria groups (all others). High-resolution computed tomography (HRCT) images were evaluated using the CT scoring system and their association with FeNO was examined.

Results: A total of 89 patients were included in the study. Compared with the nontuberculous mycobacteria group, the nontuberculous mycobacteria+BA group had higher rates of allergic disease (51.6% vs. 22.4%; p=0.0085) and higher FeNO values (median, 23 [interquartile range {IQR}, 15.0-43.0] ppb vs. median, 17 [IQR, 11.8-23.0] ppb; p=0.015). With diagnostic asthma care using mainly ICS/LABA with reference to the FeNO, most patients (91.0%, 20/22) in the nontuberculous mycobacteria-preceding subgroup in the nontuberculous mycobacteria+BA group demonstrated a prompt improvement of their symptoms and AFB culture findings did not worsen (Culture positive rate (%): Pre-treatment: 59.1% vs. Post-treatment: 40.9%, p=0.3660) at 6 months after starting diagnostic therapy. The optimal diagnostic cutoff point of FeNO to distinguish between the two groups was calculated as 21.5 ppb by the ROC curve (sensitivity 75%, specificity 71.93%, p<0.0001; area under the curve: 0.7989). No significant correlation was observed between FeNO and the severity of CT images in the patients. A certain number of patients with nontuberculous mycobacteria-PD showed exacerbated respiratory symptoms due to asthmatic complications. Elevated FeNO levels suggest asthma complications, even in patients with nontuberculous mycobacteria.

Reference:

Miki, M., Miki, K., Akiba, E. et al. The diagnostic impact of fractional exhaled nitric oxide for asthmatic cough in nontuberculous mycobacterial pulmonary disease. BMC Pulm Med 24, 210 (2024). https://doi.org/10.1186/s12890-024-03028-3