Relationship Between Airway Obstruction and Respiratory Symptoms in Adult Asthmatics: Discussion
Previous studies have demonstrated a poor relationship between asthma symptoms and objective measures of airway obstruction. The present study extends these observations to an urban-based adult population with moderate to severe asthma.
Our data demonstrate that respiratory symptoms and airway obstruction correlate poorly in adult asthmatics. Similar results have been found in prior studies. Ferguson recorded daily symptom scores and PEF over eight consecutive 2-week intervals in a cohort of 20 asthmatic children. Although symptomatic periods were closely associated with low PEF values, asymptomatic intervals were associated with reduced PEF values 54% of the time. Sly et al demonstrated that there was no significant relationship between subjective symptom scores and FEVi in a group of 14 asthmatic children, both before and after a 4-week “training period” during which PEF was measured thrice daily. Kendrick et al demonstrated that 60% of 255 adult asthma patients were poor discriminators of their underlying airway obstruction as determined by serial PEF measurements over a 2-week period. In addition to these studies, many asthmatics have been demonstrated to poorly perceive added airway resistance or airway obstruction induced by inhaled pharmacologic agents. In effect, all of these studies have emphasized the lack of sensitivity asthma symptoms have for identifying the presence of underlying airway obstruction. This seems to be particularly true for patients with high levels of bronchial hyperreactivity. In the present study, patient symptoms did not correlate with the FEVX and only poorly correlated with PEF (Figs 1, 4). In contrast to prior studies, our patients tended to more frequently overestimate their level of airway obstruction (Fig 1). Moreover, as a group, our patients reported subjective improvement in many of their asthma symptoms without concomitant improvement in their PEF values (Table 2). Our results, therefore, further emphasize the importance of using objective measures of lung function in the assessment of asthma patients. Hypothesis