Purpose: The present study aimed to develop and validate the modified patient-reported outcome scale for chronic obstructive pulmonary disease (mCOPD-PRO) for measuring the health status in COPD using both classical test theory and item response theory.
Methods: A working group was initially established. The conceptual framework of COPD-PRO was modified. Subsequently, items related to COPD were gathered and selected through expert consultation, patient cognitive interviewing, classical test theory methods, as well as the item response theory method. Finally, the formed mCOPD-PRO was evaluated in terms of reliability, content validity, construct validity, criterion validity, known groups validity, and feasibility.
Results: A total of 155 items were gathered in the item bank, and two rounds of expert consultation, interviews with patients and field survey were conducted. The mCOPD-PRO included 27 items in the physiological, psychological, and environmental domains. The Cronbach’s alpha of the instrument was 0.954. The correlation coefficients between the scores of each item and its domain scores ranged from 0.429 to 0.902. Confirmatory factor analysis showed that the comparative fit index, incremental fit index, non-normed fit index, standardized root-mean-square residual, and root-mean-square error of approximate were 0.91, 0.91, 0.90, 0.11, and 0.16, respectively. The correlation coefficient between mCOPD-PRO total scores and COPD assessment test scores and the modified Medical Research Council dyspnea scale scores was 0.771 and 0.651, respectively. The differences in mCOPD-PRO total scores and domain scores between the mild/moderate group and severe/extremely severe group of patients with COPD were both statistically significant (P < 0.01). The acceptance and completion rates of mCOPD-PRO were both 99.5%, and the median completion time was 5 min (IQR, 4– 11 min).
Conclusion: The 27-item mCOPD-PRO is well developed and has good reliability, validity, and feasibility. It may provide a scientific and effective instrument for the clinical evaluation of COPD.
Keywords: chronic obstructive pulmonary disease, patient-reported outcome, classical test theory, item response theory, instrument