Background: Chronic respiratory diseases, including chronic obstructive pulmonary disease (COPD), asthma, interstitial lung disease (ILD), and bronchiectasis, are not curable and can affect not only the patient's quality of life but also impact families and communities. We aimed to identify the association between generic self-reported Health-related quality of life (HRQoL) using the 36-Item Short Form Health Survey questionnaire (SF-36) and pulmonary function test (PFT).

Methods: A cross-sectional observational study was conducted on patients who performed PFT in Songklanagarind hospital. The SF-36 questionnaire was used to evaluate generic HRQoL. The correlation between SF-36 scores and pulmonary function parameters was analyzed.

Results:
A total of 384 patients were enrolled, of whom 213 (55.5%) were female. 64.7% of patients were non-smokers. There were 135 (35.2%), 80(20.8%), 49(12.8%), 25(6.5%), and 15(3.9%) patients with asthma, ILD, COPD, resectable lung cancer, and bronchiectasis groups, respectively. FEV₁%predicted showed a significant linear correlation with four domains: physical functioning, role limitation due to physical health, role limitation due to emotion, and general health perception in all population (p<0.05). In subgroup analyses, HRQoL of both physical and mental component summaries deteriorated only in asthma and ILD patients according to the severity of FEV₁.

Conclusion: Some domains of the HRQoL by the SF-36 questionnaire has a correlation with FEV₁%predicted. For asthma and ILD patients, the more FEV1%predicted reduce, the poorer quality of life they have.