Effect of varying the time frame for COOP-WONCA functional health status charts: a nested randomised controlled trial in Bristol, UK

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Abstract
STUDY OBJECTIVES: To investigate whether changing the stated time frame for COOP-WONCA charts has any effect on responses. Specifically, to assess the effect of attempting to avoid the situation where the time frame crosses the onset of an acute episode. DESIGN: A randomised controlled trial of two time frames, nested within a main trial comparing early discharge with a hospital at home scheme against routine discharge policy. The time frames compared were the standard two weeks (four for the pain chart) and a shorter period of 48 hours for all seven charts. SETTING: Acute hospital wards in Frenchay Healthcare Trust and the Avon Orthopaedic Centre in Bristol. PARTICIPANTS: Patients entered into the main trial, who were medically stable, in need of continued rehabilitative care but suitable for discharge to hospital at home. MAIN RESULTS: A total of 200 patients were randomised, 106 to the shorter time frame, 94 to the standard charts. No clear differences were observed between the two groups for the proportion failing to self complete the charts. For the (seven) chart scores, only pain was statistically significantly different between the time frames (Mann-Whitney p = 0.0085; proportion reporting moderate or severe pain 19% higher in the standard group, 95% confidence intervals 5% to 33%). For both this chart and that for change in health, however, there was evidence of greater differences between the versions of the chart among those admitted more recently (p values for relevant interactions 0.004 and < or = 0.001 respectively). CONCLUSIONS: While the present findings give some support for the wide applicability of the standard version, there is sufficient evidence here to indicate that the time frame may influence the results, particularly for patients with a recent acute episode. In the absence of further data, then, it would seem prudent to consider a shorter time frame for such patients, especially if the aim is to assess current health status or to measure changes over a comparatively short period of time, or both.