Interpreting quality-of-life data: methods for community consensus in asthma

Change in healthrelated quality of life (HRQoL) is an important outcome in asthma treatment. Patient and provider consensus on how to determine thresholds for identifying important improvements and declines, however, has not been achieved. To search for consensus in clinically important difference (CID) thresholds for HRQoL change from 3 points of view: (1) an expert panel of physicians who treat patients with asthma and measure the HRQoL of their patients, (2) asthmatic patients, and (3) the primary care physicians (PCPs) of these asthmatic patients. The expert panel used Delphi and consensus methods to agree on CID levels for the Asthma Quality of Life Questionnaire and the Medical Outcomes Study 36-Item Short-Form Health Survey, version 2.0. A total of 396 patients attending midwestern primary care clinic sites completed these interviews bimonthly for 1 year. The 46 PCPs treating these patients completed baseline assessments on each patient's asthma and then evaluated the change in each patient's condition at subsequent office visits during the next year. The patient-perceived estimates were consistent with results of previous studies but were notably lower than those derived from the expert panel and the PCPs. The Short-Form Health Survey generally did not provide sufficient sensitivity to detect important changes. Although consensus on the interpretation of change in HRQoL measures was not achieved, this evidence-based approach demonstrates the value of patient and physician perspectives and the need for improved dialogue and understanding to optimize the HRQoL of patients with asthma.