Fourteen symptoms, which can be described in patients' daily diaries, provide a new model for quantifying exacerbations in chronic obstructive pulmonary disease (COPD).
Called the Exacerbations of Chronic Pulmonary Disease Tool (EXACT), the 14-item list includes:
- breathless today
- how breathless today
- shortness of breath with personal care
- shortness of breath indoors
- shortness of breath outdoors
- cough today
- mucus when coughing
- chest congested
- chest discomfort
- chest tight
- difficulty with mucus
- sleep disturbed
In order to select the items, researchers identified 23 symptoms from patient interviews administered to 410 patients with COPD with an average stable FEV1 of 51% predicted and 1.8 exacerbations in the preceding 12 months. Results appeared in the June issue of Chest.
A total of 222 patients had a physician-diagnosed exacerbation; 188 were stable. Item-level analyses were used in the first stage analyzing 23 criteria. One item was excluded due to poor performance across multiple criteria. A Rasch model was conducted to screen the remaining 22 items for fit to a unidimensional construct. Eight items were removed because of a less-than-good performance. None of the surviving 14 items showed evidence of differential item functioning between stable and exacerbation states (analysis of variance P >0.05 in each case). Internal consistency (person separation index) was excellent at 0.92. Post hoc exploratory factor analysis revealed one dominant factor, with three domains (breathlessness, cough and sputum, and chest symptoms) that accounted for 68% of the variance.
“Previous symptomatic definitions have been limited to the cardinal symptoms of cough, sputum, and breathlessness, but this comprehensive assessment demonstrates that exacerbation symptoms show a much broader spectrum than previously recognized,” the authors wrote, concluding that the newly-developed tool can be used successfully to quantify COPD exacerbation severity.