PURPOSE: The purpose of this study is to develop and validate a user friendly patient-completed COPD tool that predicts COPD stability in patients who already have a COPD diagnosis.
METHODS: A working group of COPD and patient-reported outcomes specialists was convened and patient interviews were conducted to generate a 21-item questionnaire. These items were administered to 395 COPD patients naïve to the specialist from 7 sites across the US. A physician’s global rating of stability was recorded which took into consideration different components including pulmonary function tests, COPD symptoms and exacerbation, COPD impact on activities of daily living and on emotional functioning, health-related resource utilization and smoking status. Using data of 75% of the subjects (“development sample”), stepwise binary logistic regression models were used to identify the items which are able to best discriminate a patient’s stability status as defined by the physician’s rating (Stable = “Completely Stable”). Based on clinician input, additional items that dealt with symptoms often queried by physicians were tested for inclusion in the final tool using additional logistic models. Validation analyses were conducted including internal consistency reliability, discriminant validity, known-groups validity and sensitivity/specificity analyses.
RESULTS: Five items (documenting emotional functioning, symptom frequency and resource utilization) were selected for inclusion into the final COPD assessment tool. The internal consistency reliability of the questionnaire was 0.74. The five items in the COPD assessment tool discriminated between groups of patients differing in the physician’s rating of COPD stability (F=44.26; p<0.0001), the percent predicted pre-bronchodilator FEV1 (F=4.90; p<0.01), and the percent predicted post-bronchodilator FEV1 (F=2.92; p<0.05). The COPD assessment tool was able to predict “complete stability” with an overall area under the ROC curve (AUC) of 0.83.
CONCLUSION: This study demonstrates that the COPD assessment tool is a valid, reliable and practical patient-based measure of COPD stability.
CLINICAL IMPLICATIONS: This tool may provide physicians valuable quantitative information regarding the impact of the disease on individual patients which may foster communication between patients and physicians regarding patient’s COPD stability.
DISCLOSURE: Jacqueline Carranza Rosenzweig, Employee GSK.