Reliability and validity of the COOP/WONCA health status measure in patients with chronic obstructive pulmonary disease.

The objective of the study was to assess the reliability and validity of the Dartmouth Primary Care Cooperative Information Project/World Organization of National Colleges, Academies, and Academic Associations of General Practice/Family Physicians (COOP/WONCA) questionnaire in outpatients with chronic obstructive pulmonary disease (COPD). The test-retest reliability of individual items of the COOP/WONCA questionnaire was assessed using a weighted kappa-statistic, and construct validity was assessed by correlating items of the COOP/WONCA with the EQ-5D health status measure. Discriminant validity was assessed by comparing scores for known groups, at the same time comparing the results with those of a lung-specific health status questionnaire. The individual items of the COOP/WONCA had test-retest reliabilities of 0.67-0.78 (weighted kappa). Spearman's rank correlations between COOP/WONCA single-item scores and corresponding EQ-5D ranged 0.45-0.72, which were generally higher than associations between non-corresponding items. Four of the five COOP/WONCA items did not discriminate between patient groups divided according to forced expiratory flow in 1 sec (FEV1) in percent of predicted and 6-min walking distance, while four of five items of the lung-specific questionnaire discriminated well between these groups. The COOP/WONCA chart system was reliable and showed properties supporting the construct validity of the measure. The items, however, did not discriminate well between known groups, indicating that this questionnaire is not very sensitive in patients with COPD. The reliability of the COOP/WONCA items was acceptable for use at group level, but lower than current recommendations for use in individual patients.