Relationship between airway obstruction and respiratory symptoms in adult asthmatics

Study objectives: To characterize the relationship between symptoms and the degree of airway obstruction as determined by the FEV1 and peak expiratory flow (PEF) in a cohort of adult patients attending a university-based urban asthma clinic. Design: Each of six current asthma symptoms, including cough, dyspnea, wheeze, chest tightness, sputum production, and nocturnal awakening was rated by patients on a 0 (none) to 4 (constant) scale at initial and first follow-up clinical evaluations. Spirometry and PEF were measured at the initial clinical visit and PEF was measured at all follow-up visits. Patients: Sixty-seven adult patients with chronic asthma. Measures and results: Asthma symptoms did not correlate with the degree of airway obstruction as determined by the FEV1 (percent predicted FEV1 vs total symptoms: r=0.143; p=0.263; n=70) and only correlated poorly with PEF (percent predicted PEF vs total symptoms: r=0.384; p=0.0029; n=58). Subjective wheezing was the best individual predictor of the level of airway obstruction in this group of patients. When reassessed an average of 7.9 weeks later, patients reported significant improvement in several symptoms, including those of wheeze, chest tightness, dyspnea, and nocturnal awakening. However, this symptomatic improvement was not associated with improvement in the level of airway obstruction. Conclusions: Asthma symptoms correlate poorly with the level of airway obstruction as determined by the FEV1 and PEF. Following treatment, subjective improvement in asthma symptoms may occur without improvement in the level of airway obstruction. These results support the recommendation to measure airway obstruction objectively when assessing adult patients with chronic asthma.