COPD and Asthma Fatigue Scale (CAFS): Development and Psychometric Assessment

Abstract

Objectives

Patients with respiratory diseases report significant fatigue, but few measures have been developed to assess respiratory disease-related fatigue in patients with either asthma or chronic obstructive pulmonary disease (COPD). This study developed and evaluated the psychometric characteristics of the COPD and Asthma Fatigue Scale (CAFS), a respiratory disease-targeted scale.

Study Design

Patient qualitative data (focus groups and individual interviews) with COPD and asthma patients were used to generate the CAFS. An observational study involving patients with asthma or COPD from the US and UK was then conducted to assess the psychometric qualities of the CAFS. COPD patients completed the St. George’s Respiratory Questionnaire, asthma patients completed the Asthma Quality of Life Questionnaire, and selected clinical severity measures were collected for all patients.

Results

Qualitative data were obtained from 78 patients with COPD and 84 with asthma. The observational study included 311 patients with COPD and 324 with asthma. The final 12-item CAFS was confirmed based on factor and item analyses. Internal consistency was 0.95 (both groups) and test-retest reliability was 0.82 and 0.84 (COPD and asthma, respectively). In COPD patients, CAFS scores were significantly correlated with St. George’s Respiratory Questionnaire scores (P <.0001); mean CAFS scores varied significantly by disease severity, exacerbations, and health status (P ≤.0014). In asthma patients, CAFS scores were significantly correlated with Asthma Quality of Life Questionnaire scores (P <.0001); mean CAFS scores varied significantly by disease severity, exacerbations, and health status (all P ≤.0024).

Conclusions

The CAFS was developed using systematic qualitative and psychometric methods and is a reliable and valid measure of fatigue in asthma or COPD patients.