Health-related quality of life in a multiracial Asian interstitial lung disease cohort

Background: Understanding health-related quality of life (HRQL) in patients with interstitial lung disease (ILD) provides insight into disease burden and treatment effects on patients' well-being. We examined HRQL in a multiracial Asian ILD cohort using the King's brief ILD (K-BILD) and EuroQol 5-dimension-3-level (EQ5D-3L) questionnaires and their associations with several clinical variables. Methods: This was a single-centre cross-sectional study of ILD patients in a university-affiliated tertiary public hospital in Singapore. All patients completed two self-administered HRQL questionnaires upon study entry, and their clinical information was retrieved from electronic medical records. Results: Ninety-nine patients (56% male, 75% Chinese) were included. The median (interquartile range) age was 63 (54-72) years. The most common ILD diagnosis was connective tissue disease-related ILD (n=51, 52%), followed by idiopathic pulmonary fibrosis (n=27, 27%). The mean (standard deviation) scores for the EQ5D-3L utility value, EQ5D Visual Analogue Scale (VAS) and K-BILD total were 0.806 (0.284), 75.1 (12.8) and 63.9 (14.3), respectively. A moderate correlation was found between the EQ5D-3L and K-BILD total and domain scores. The HRQL scores also correlate moderately with the modified Medical Research Council dyspnoea scale (mMRC) scores. There was a weak-to-moderate correlation between HRQL and forced vital capacity (FVC), carbon monoxide diffusing capacity (DLCO) and Charlson comorbidity index. Multiple linear regression showed a significant association of K-BILD total [beta coefficient 0.244, 95% confidence interval (CI): 0.075-0.414; P=0.005], K-BILD 'breathlessness and activities' (beta coefficient 0.448, 95% CI: 0.192-0.703; P=0.001), and the 'psychological' domain (beta coefficient 0.256, 95% CI: 0.024-0.488; P=0.031) with DLCO %pred after adjustment for age, sex, BMI, race, smoking history, comorbidities, FVC %pred and ILD diagnosis. Non-Chinese race was a predictor of better K-BILD 'psychological' domain (beta coefficient 8.680, 95% CI: 0.656-16.704; P=0.034) after adjustment. Conclusions: HRQL is significantly impaired in ILD patients, and low DLCO is a strong predictor of this impairment.