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

The objective of this study was to assess the performance of a lung-specifi c health status measure in patients with chronic obstructive pulmonary dise ase (COPD). We used the Respiratory Quality of Life Questionnaire (RQLQ), a modification of an Australian questionnaire intended for asthma patients a nd 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, va lidity and responsiveness in 59 outpatients attending a Norwegian hospital for COPD. Statistical analysis included internal consistency, test-retest r eliability and convergent validity between the two questionnaires. Responsi veness was assessed in patients reporting global change in health status ov er 1 year. All scales of the RQLQ showed good internal consistency (Cronbach's a=0.85- 0.94) and test-retest reliability (intraclass correlation coefficient=0.86- 0.94), as did the SF-36 scales (a=0.66-0.90 and intraclass correlation coef ficient=0.60-0.86). Pearson correlations between scales with similar items ranged from 0.54 to 0.76, supporting the construct validity of both questio nnaires. 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 valid ity and responsiveness in COPD patients, encouraging further use of this qu estionnaire.