In this study, the BACES score was related to HRQOL and associated clinical factors in patients with NTM-PD who initiated antibiotic treatment. The scoring system correlated with patients’ symptoms, perceived well-being, malnutrition, body composition, lung function, 6MWD, and handgrip strength. The odds of adipopenia increased according to the BACES score in men and the odds of adipopenia and sarcopenia also increased according to the BACES score in women. Therefore, the BACES score can be used as a predictor for HRQOL and associated factors in patients with NTM-PD at the start of antibiotic treatment.

HRQOL is a multifaceted concept in which biological and physiological variables, symptoms, functional status, and general health perceptions are closely integrated with individual and environmental characteristics21. As diverse clinical conditions can affect HRQOL along with sociodemographic factors22,23, a holistic approach is required to measure HRQOL. The NTM-KOREA study comprehensively evaluated HRQOL and associated factors by incorporating symptom assessment, questionnaires, laboratory tests, and physical measurements.

Various generic or disease-specific tools have been developed to measure HRQOL24. For instance, St George’s Respiratory Questionnaire, the Leicester Cough Questionnaire, and the QOL-B are widely used in bronchiectasis with good validity, internal reliability, and repeatability25. However, no standard instruments have been developed for NTM-PD. Recent studies have used the QOL-B, NTM Module, and Patient-Reported Outcomes Measurement Information System Fatigue 7a to measure HRQOL in patients with NTM-PD26,27,28. In this study, we used the QOL-B questionnaire to measure HRQOL in patients with NTM-PD. As the BACES score increased, HRQOL measured using the QOL-B was poorer in many domains including respiratory symptoms. Regarding HRQOL, malnutrition and sarcopenia are two important health conditions. Nutritional status plays a pivotal role in preserving and improving HRQOL in the aged population29. Nutritional status is known to affect the development and progression of NTM-PD30. We found a high proportion of patients being at risk of malnutrition even in the BACES mild group (score: 0–1), and the odds of malnutrition increased along with BACES score. Sarcopenia, i.e., decline in muscle mass and function, results in increased levels of dependency and disability. Consequently, HRQOL in individuals with sarcopenia is markedly impaired compared with that in individuals without sarcopenia31. Sarcopenia can lead to several harmful health consequences including falls, fractures, hospitalization, and death. We found a considerable proportion of possible sarcopenia and sarcopenia cases in the BACES moderate (score: 2–3) and severe (score: 4–5) groups. Moreover, the odds of sarcopenia were positively associated with the BACES score in women. Taken together, our results suggest that the BACES score reflects HRQOL and associated clinical factors in patients with NTM-PD.

However, the BACES score alone may be limited in fully capturing HRQOL and associated factors. While our study found that HRQOL was lower among patients with higher BACES scores, it is important to note that even some patients with lower BACES scores experienced compromised HRQOL. Therefore, clinicians should be aware that patients with NTM-PD may experience substantial impacts on their HRQOL, warranting HRQOL assessment regardless of disease severity. Further research is needed on the development of more sophisticated assessment tools to better evaluate HRQOL in patients with NTM-PD. In addition, multidisciplinary strategies for improving HRQOL through both pharmacologic and non-pharmacologic interventions are necessary.

According to a recent study, physical inactivity was more prevalent in individuals with NTM-PD than in the general population. Moreover, physical inactivity was associated with disease severity, as evidenced by the presence of cavities, disease extent, and treatment requirement32. However, our results did not reveal a relationship between physical activity and the BACES score. The reasons for this disparity could lie in the study population and assessment tool. Our study was restricted to participants who were initiating antibiotic treatment, and the measurement tool, IPAQ-SF, has not been validated for patients with NTM-PD. Further research would be required using a fitness tracker in various stages of NTM-PD.

Current guidelines recommend a ‘watchful waiting’ approach rather than immediate treatment following the diagnosis of NTM-PD in selected cases4. However, clear guidance and detailed methods for managing this observation period remain lacking. A recent study has shown that HRQOL improved with NTM treatment, especially in patients with poor baseline HRQOL33. Additionally, higher BACES severity is associated with a lower spontaneous culture conversion rate15. Considering these findings and our results, the BACES score may serve as an indirect yet convenient tool for determining treatment strategies for NTM-PD, addressing not only microbiologic outcomes but also patient-centered aspects. Specifically, early treatment initiation might be considered in patients with higher BACES scores. However, the BACES score is limited in evaluating changes in HRQOL due to treatment. The erythrocyte sedimentation rate, BMI, and cavity presence are the only variables that could be changed from all components that comprise the BACES score. Further research will be needed as more data from the NTM-KOREA cohort becomes available.

The principal strength of this study is its prospective design, which captured the actual experiences of patients with NTM-PD in a clinical setting. Patients from referral hospitals representative of all regions of South Korea were also included, which enhances the generalizability of our findings. Unlike previous studies that primarily evaluated the BACES score for predicting mortality or microbiological outcomes, our study expanded its application to patient-centered metrics such as HRQOL, nutritional status, and sarcopenia. This broadens the clinical relevance of the BACES score and makes our findings more applicable in real-world practice.

However, this study has some limitations. First, although we used data from a prospective cohort, the present analysis was cross-sectional. Second, all measurements were obtained within four weeks of the initiation of antimycobacterial therapy. Therefore, extrapolation to patients managed with watchful waiting should be performed with caution. Nonetheless, the combined evidence from our findings and previous reports—showing that higher BACES scores predict faster disease progression—indicates that the score may serve as a convenient predictor to support treatment decisions in the post-diagnosis phase13. Future studies that follow both treated and untreated cohorts will be essential for confirming this role. Lastly, as age and BMI are inherently included in the BACES score, we did not adjust for them separately in our analysis. Supplementary analyses showed that BMI (plus age) did not significantly outperform the BACES score in predicting outcomes, such as adipopenia, sarcopenia, and symptoms. This approach preserves the original structure and interpretability of the score, although the potential influence of age and BMI on the outcomes should still be considered.

In conclusion, the BACES score was related to HRQOL and associated factors in patients with NTM-PD requiring treatment. HRQOL and associated clinical conditions were significantly compromised, and the strong relationship between higher BACES scores and poor HRQOL persisted after adjusting for confounding variables. Therefore, the BACES score can be considered a supplementary tool to evaluate HRQOL and associated clinical factors at the start of treatment in patients with NTM-PD.