OBJECTIVES:

The King’s Brief Interstitial Lung Disease questionnaire (K-BILD), a disease-specific quality of life questionnaire (QoL) for individuals with interstitial lung disease (ILD) has not been applied in a German setting yet. Thus, a comparison of K-BILD with the well-established EQ-5D-5L could show its usability in clinical settings.

METHODS:

We calculated mean of EQ-5D-index and visual analog scale (VAS) and K-BILD alongside with their correlation in total score and in different domains for 239 patients with different ILD entities from the longitudinal observational HILDA study. Additionally potential predictors (age, sex, ILD entity, FVC percentage of predicted value (FVC%), DLCO percentage of predicted value, and either sum of comorbidities (model1) or distinct comorbidities (model2)) for QoL were investigated with linear regression models.

RESULTS:

Means were as follows EQ-5D-index 0.79 (SD 0.18), VAS 60.4 (SD 19.3) and K-BILD 53.4 (SD 11.5).

EQ-5D and K-BILD showed moderate positive correlations (EQ-5D-index vs. K-BILD 0.61; VAS vs. K-BILD 0.57). The “breathlessness and activities” K-BILD domain highly correlated with the “usual activities” (-0.70) and “mobility” domain (-0.66) of EQ-5D index. Other domains showed moderate correlations.

In model1 higher FVC% was associated with higher QoL (EQ-5D index 0.0028 p=0.0001; VAS 0.26 p=0.0006; K-BILD 0.16 p=0.0007) whereas comorbidity burden decreased QoL (EQ-5D index -0.032 p=0.0015; VAS: -3.14 p=0.0034; K-BILD -2.13 p=0.001).

In model2 FVC% showed similar results (0.0023 p=0.0005; 0.0023 p=0.0021; 0.16 p=0.0009). Heart Insufficiency and Diabetes Mellitus influenced EQ-5D-index (0.13 p=0.0354; -0.0087 p=0.008) and Depression decreased K-BILD (-6.46 p=0.023). Other factors had no significant influence.

CONCLUSIONS:

K-BILD and EQ-5D score reveal similar QoL trends and are sensible to the same disease-related factors. K-BILD reacts more sensitively to ILD-specific aspects of QoL rendering it a valuable complementary measure to EQ-5D-5L which is usually recommended for health care decision making.