Creating scenarios of the impact of copd and their relationship to copd assessment test (CAT？) scores

A Bland and Altman plot showed a consistent relationship between CAT scores and scores obtained with the St George's Respiratory Questionnaire for COPD (SGRQ-C) permitting a direct mapping process between CAT and SGRQ items. The severity associated with each CAT item was calculated using a probabilistic model and expressed in logits (log odds of a patient of given severity affirming that item 50% of the time). Severity estimates for SGRQ-C items in logits were also available, allowing direct comparisons with CAT items. CAT scores were categorised into Low, Medium, High and Very High Impact. SGRQ items of corresponding severity were used to create scenarios associated with each category.Each CAT category was associated with a scenario comprising 12 to 16 SGRQ-C items. A severity 'ladder' associating CAT scores with exemplar health status effects was also created. Items associated with 'Low' and 'Medium' Impact appeared to be subjectively quite severe in terms of their effect on daily life.These scenarios provide users of the CAT with a good sense of the health impact associated with different scores. More generally they provide a surprising insight into the severity of the effects of COPD, even in patients with apparently mild-moderate health status impact.Understanding a chronic obstructive pulmonary disease (COPD) patient's health status is an integral part of overall patient management. International guidelines on the management of COPD recommend that both lung function and health status are monitored regularly to guide any changes in treatment [1], and both the European Respiratory Society and the American Thoracic Society recommend that health status should be assessed as an outcome in clinical trials of new and existing pharmacological therapies for treatment of COPD [2]. A number of different questionnaires are available that assess health status in COPD, these include the Chronic Respiratory Questionnaire (CRQ) [3], the Clinical COPD Questionnaire (CCQ) [4],