Quality of Life in inflammatory bowel disease: biases and other factors affecting scores.

Health-Related Quality of Life (HRQOL) measurement has become a key element in the assessment of chronic diseases during the execution of clinical research and in the delivery of health care. Poor HRQOL is clearly recognized in patients with inflammatory bowel disease (IBD) and relates to the type of disease (Crohn's disease or ulcerative colitis) and disease severity. It is also linked to non-disease elements e.g., gender, age, personality, cultural factors and coping skills. The dynamic properties of HRQOL may be depicted using different measurement tools and the portrayal may well differ when using a generic- or a disease-specific instrument. HRQOL status also changes with time, as do disease and non-disease parameters. Several examples of population selection bias are demonstrated using the Sickness Impact Profile (SIP), the time trade-off and the McMaster Inflammatory Bowel Disease Questionnaire (IBDQ). While HRQOL is generally good in IBD patients, mean HRQOL scores are still significantly depressed compared to normal controls. The IBDQ, a disease-specific HRQOL instrument, has yielded consistent results in both cross-sectional studies and prospective clinical trials. Such HRQOL instruments can be used to identify the types of new therapies that are needed, subgroups of patients which might benefit from specific treatments, patient satisfaction, treatment efficacy and efficiency. These applications must always be undertaken with careful attention to rigorous research methodology.