Clinical application of a simple questionnaire for the differentiation of asthma and chronic obstructive pulmonary disease.

Background: Asthma and chronic obstructive pulmonary disease (COPD) are highly prevalent chronic diseases characterized by airflow limitation. Both diseases have a distinct pathogenesis and require unique treatment approaches. Due to some common characteristic traits, asthma and COPD are often lumped together in clinical practice. We sought to develop a simple questionnaire for the distinction of asthma and COPD.

Methods: Clinical discriminants of asthma and COPD were retrospectively identified by multiple logistic regression using files from 547 consecutive adult patients presenting to a pulmonary specialist practice with a diagnosis of asthma or COPD. With these features, we generated a simple quantitative questionnaire supporting a diagnosis of COPD with high scores and asthma with low scores (range 0-15 points). Questionnaire results were compared with physician's diagnosis based on GINA and GOLD guidelines including skin tests, spirometry and reversibility data.

Results: 210 patients had COPD and 337 had asthma. Age of onset, smoking history, atopy status, and cough quality were significantly associated with a diagnosis of asthma or COPD. Questionnaire scores for COPD patients were higher than those for asthmatics (mean score 10.5+/-0.18 vs. 4+/-0.12, P<0.0001). Receiver operational characteristics (ROC) analysis revealed a cutoff score of 7 with the highest discriminant power (87.6% sensitivity, 87.2% specificity for COPD, 87.4% correctly classified, area under the ROC curve: 0.954). The overlap between asthma and COPD (score 6-8) comprised about 20% of the total population, these patients included a higher proportion of COPD patients with atopy, and smoking asthmatics.

Conclusions: In patients with obstructive airway diseases, a simple questionnaire can support the differentiation of asthma and COPD in everyday clinical practice. Further prospective trials are necessary to confirm these initial observations.