Measuring functional health status in primary care using the COOP-WONCA charts: acceptability, range of scores, construct validity, reliability and sensitivity to change.

Abstract

BACKGROUND. The COOP-WONCA charts comprise six scales designed to measure functional health status in primary care. AIM. A study was undertaken to describe the acceptability, distribution of chart scores, construct validity, test-retest reliability and sensitivity to change when these charts were used in the United Kingdom. METHOD. For acceptability, distribution of scores and construct validity, data were obtained from 100 consecutive consulting patients aged 16 years and over and 100 non-consulting age-sex matched individuals from one general practice. In order to examine reliability and sensitivity to change, both groups were followed up two weeks later. RESULTS. Regarding acceptability, four patients refused to complete the charts during the initial recruitment of the consulters; 74 out of 100 non-consulters returned the first postal questionnaire. The follow-up questionnaire was returned by 68 out of 100 consulters and 57 out of 74 non-consulters. Overall distributions of scores demonstrated reasonable variation. Regarding construct validity, differences between the consulters and non-consulters were all in the anticipated direction and reached statistical significance for three of the six charts. For reliability, the proportion of non-consulters whose scores were unchanged ranged from 56% to 73%. For those whose scores changed, the differences were small and evenly balanced. For sensitivity to change, the proportion of consulters whose scores altered ranged from 45% to 59% with mean changes all indicating improvements in health. There were larger changes for patients consulting about acute problems than for those with chronic problems. CONCLUSION. It appears that the charts were acceptable, with reasonable distributions of scores and evidence of construct validity. Moderate levels of reliability and sensitivity to change were demonstrated. This study suggests that the COOP-WONCA charts are suitable for measuring functional health status in primary care in the UK.