Clinical data discriminating between adults with positive and negative results on bronchodilator testing

OBJECTIVE: To evaluate how spirometry, symptoms and smoking discriminate between subjects who are responsive to bronchodilator testing and those who are non-responsive, and to examine how cut-off points of positive tests are related to symptoms of chronic obstructive pulmonary disease (COPD) and asthma.

METHODS: Subjects aged 47–48 and 71–73 years living in Bergen, Norway, were recruited. The 3506 participants (69%) filled in questionnaires and performed a bronchodilator test using salbutamol.

RESULTS: Tests were positive (forced expiratory volume in 1 s [ΔFEV₁] ≥200 ml and ≥12%) in 107 subjects (3%). In logistic regression, spirometry (FEV₁ < 80%, OR 6.0, 95%CI 3.6–10.2, and FEV₁/FVC < 0.70, OR 3.1, 95%CI 1.9–5.2) and pack-years ≥ 20 (OR 0.3, 95%CI 0.2–0.7), but not symptoms, predicted the test outcome. FEV₁% and FEV₁/forced volume capacity (FVC) discriminated equally well between positive and negative tests (area under the receiver operating characteristic [ROC] curve 0.81, 95%CI 0.77–0.85 vs. 0.77, 95%CI 0.72–0.82). The largest likelihood ratio for positive tests was 5.4 (95%CI 3.8–7.8) using FEV₁ < 80% and FEV₁/FVC < 0.70.

CONCLUSIONS: Spirometry and to a lesser extent smoking, but not symptoms, are useful in discriminating between middle-aged and elderly patients with positive and negative bronchodilator tests. Acute responses to salbutamol, expressed by commonly used ΔFEV₁ cut-off points, are poorly related to COPD- and asthma-like symptoms.