Portuguese version of the King’s Brief Interstitial Lung Disease questionnaire: measurement properties

Abstract

The King’s Brief Interstitial Lung Disease (KBILD) assesses the health-related quality of life (HRQoL) in ILD. Its measurement properties are not fully understood, hindering its widespread use. Reliability and validity of its European Portuguese version were assessed.

In this cross-sectional study, KBILD, St. George’s Respiratory Questionnaire-IPF (SGRQI), London Chest Activities of Daily Living (LCADL), lung function (FVC%p and DLCO%p) and 6-min walk distance (6MWD) were acquired at baseline. KBILD was repeated 48-72h via phone call by two raters.

195 people with ILD (63±14 years; 47% male; FVC%p 87±20; DLCO%p 65±23) were included. KBILD showed good to excellent internal consistency (α=0.74-0.92), test-retest (ICC=0.80-0.86) and inter-rater (ICC=0.92-0.97) reliability and good agreement between raters, without evidence of systematic bias. SEM and MDC95 ranged between 0.79-1.70 and 2.20-4.72, respectively. Correlations between KBILD and: SGRQI were significant, negative and moderate to high (ρ=-0.48 to -0.86;p<0.01); LCADL were significant, negative and moderate to high (ρ=-0.48 to -0.72;p<0.01); lung function and 6MWD were significant, positive and small to moderate (ρ=0.23;p<0.05 to 0.50;p<0.01). Ceiling effect was found for psychological and chest symptoms domains. Its discriminant validity was demonstrated (Fig. 1).

The European Portuguese KBILD is a reliable and valid questionnaire to assess HRQoL in ILD.