Development and validation of a short questionnaire in community acquired pneumonia

Background: A short but sensitive questionnaire evaluating changes in respiratory symptoms and well being during the treatment of community acquired pneumonia ( CAP) is needed. We have developed a measurement and evaluated its psychometric properties in 67 patients admitted with CAP. Methods: The patients were asked to indicate the presence and severity of dyspnoea, coughing, coughing up sputum, coughing up sputum with ease, the colour of the sputum, fatigue, fitness, and their state of health. The item fatigue showed substantial overlap with fitness and was therefore excluded. The response of the patients to the remaining eight items was used to calculate a CAP score. Results: The percentage of missing data (0.2-1.7%), floor and ceiling effects (0.2/5.5%), internal consistency (Cronbach alpha = 0.87), and the intraclass correlation coefficient for test-retest reproducibility (0.83) met predefined criteria, indicating good acceptability and reliability. Face and clinical validity were satisfactory. Effect sizes under treatment were large, indicating high responsiveness. Conclusion: The newly developed CAP score is a simple, reliable, valid, and highly responsive instrument. This makes it scientifically sound and clinically relevant for measuring outcome when evaluating treatment strategies in CAP.