Generic versus disease-specific instruments in quality-of-life assessment of chronic obstructive pulmonary disease.

OBJECTIVES: Chronic respiratory diseases may alter a patient's social life and well-being. Measures of health-related quality of life have been proven to bring complementary information to functional assessments. The aim of the study was to describe the questionnaires that are most frequently used to measure this subjective construct in patients with chronic obstructive pulmonary disease (COPD) and to compare the responses obtained via administering one generic (SF-36) and one disease-specific questionnaire (St. George's Respiratory Questionnaire; SGRQ) to patients with COPD.
METHODS: One group of patients (46 individuals) was used to evaluate the questionnaire's performance in repeated administrations under unchanged conditions (reproducibility) and to study the correlations of corresponding domains of respective questionnaires. Responsiveness of both questionnaires was tested on another group of 129 patients measured before and after the therapeutic stay at the spa. Methods of correlational analysis (Spearman, intraclass, and canonical correlation coefficients) as well as the Wilcoxon rank test were used for statistical analysis.
RESULTS: Both questionnaires seem to be comprehensive outcome measures for patients with COPD, but some particular areas may not be covered with the same intensity (e.g. emotional problems). Reproducibility of both questionnaires was good and only small non-significant shifts were seen, particularly in physical and social functioning domains. In repeated measurement, the SGRQ seemed to be slightly more responsive to change than the SF-36.
CONCLUSIONS: The idea of using generic and disease-specific questionnaires together probably represents the best approach to this topic. It may improve our knowledge and explain better the relationship between disease-specific changes in patient status and both disease-specific treatment and general functional status.