Performance of a short lung-specific health status measure in outpatients with chronic obstructive pulmonary disease

Abstract

The objective of this study was to assess the performance of a lung-specific health status measure in patients with chronic obstructive pulmonary disease (COPD). We used the Respiratory Quality of Life Questionnaire (RQLQ), a modification of an Australian questionnaire intended for asthma patients and adapted in this study to fit patients with COPD also. For comparison we chose the general health profile measure Short Form 36 (SF-36). We assessed the five RQLQ scales and eight SF-36 scales for reliability, validity and responsiveness in 59 outpatients attending a Norwegian hospital for COPD. Statistical analysis included internal consistency, test-retest reliability and convergent validity between the two questionnaires. Responsiveness was assessed in patients reporting global change in health status over 1 year. All scales of the RQLQ showed good internal consistency (Cronbach's α=0·85-0·94) and test-retest reliability (intraclass correlation coefficient=0·86-0·94), as did the SF-36 scales ( α=0·66-0·90 and intraclass correlation coefficient=0·60-0·86). Pearson correlations between scales with similar items ranged from 0·54 to 0·76, supporting the construct validity of both questionnaires. The RQLQ had responsive scales, showing significant changes in the expected direction over 1 year. We conclude that the RQLQ showed an acceptable reliability, construct validity and responsiveness in COPD patients, encouraging further use of this questionnaire.