Translation and validation of the King's Brief Interstitial Lung Disease (K-BILD) questionnaire in French, Italian, Swedish, and Dutch.

No disease-specific instruments exist in Dutch, French, Italian, and Swedish to measure health status in idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases (ILDs). The King's Brief Interstitial Lung Disease (K-BILD) is a 15-item validated questionnaire assessing health status in patients with ILD. The aim of this study was to translate and validate the K-BILD to French, Italian, Swedish, and Dutch versions. The K-BILD was translated following a forward-backward multistep procedure and tested in structured patient interviews. Subsequently, 195 outpatients with ILD were asked to complete K-BILD, St. George's Respiratory Questionnaire (SGRQ), and Euroqol EQ-5D-5L (EQ5D), twice, 2 weeks apart. Internal consistency, concurrent validity, and repeatability were determined. No major difficulties occurred in the translation processes. The K-BILD was considered comprehensible and relevant by patients. One hundred seventy-six patients (108 IPF and 68 other ILDs) completed the translated K-BILD. Internal consistency was good for all K-BILD modules (Cronbach's α 0.70-0.93). Concurrent validity of K-BILD was strong compared with SGRQ ( r = -0.86) and EQ5D ( r = 0.68), low with transfer capacity of the lung for carbon monoxide corrected for hemoglobin ( r = 0.33) and with forced vital capacity ( r = 0.35). The K-BILD and its domains were repeatable over 2 weeks; intraclass correlation coefficients were 0.86-0.93 ( n = 159). Known groups validity showed K-BILD was able to discriminate between patients based on severity of disease. K-BILD's validity and reliability for patients with IPF was similar to that of other ILDs. The French, Italian, Swedish, and Dutch translated K-BILD questionnaires were well-received by patients and demonstrated excellent validity comparable to the original English K-BILD.