A Framework for Assessing Impairment from Asthma: Definitions of Asthma (2)
A variety of different approaches have been used to identify asthmatic subjects (Table 2). These different approaches are reviewed with particular emphasis on physician evaluation, questionnaire assessment of symptoms, and testing for bronchial responsiveness with a bronchoconstric-tor agent.
Physicians’ diagnoses of asthma are nonstandardized. In addition, there is evidence in adults and children that physicians may underdiagnose asthma. Specifically, many wheezing subjects with documented bronchial responsiveness do not receive a diagnosis of asthma and do not receive bronchodilator therapy. A physicians diagnostic label may be influenced by the patients age, smoking history, allergy status, and level of lung function, all of which are known to be associated with levels of bronchial responsiveness. Finally, many individuals who have symptoms may refuse to visit a physician for a variety of reasons, thus potentially biasing a physicians diagnosis to the more extreme cases. asthma inhalers
A questionnaire history of wheezing presents different problems. The prevalence of wheezing exceeds the prevalence of asthma. This is in part due to diagnostic bias on the part of physicians, but it is also due to lack of specificity of wheezing in its relationship to bronchial responsiveness.
Table 2—Approaches for Identifying Persons with Asthma
|Clinical evaluation||1. Nonstandardization of physician criteria for diagnosis|
|2. Bias toward more severe cases|
|3. Bias by access to physician|
|Questionnaire history of diagnosis||Same as above, plus recall bias by subjects|
|Questionnaire history of symptoms||Possibly influenced by frequency of other symptoms; less specific than doctor s diagnosis|
|Response to bronchodilator||May be influenced by level of FEV, correlation with bronchodilator; may lack sensitivity|
|Bronchoconstrictor response||Influenced by level of FEV,; may be nonspecific|