Asthma not found in high percentage of adults who were previously diagnosed

Diagnosis of asthma in the community can be difficult. Various types have been identified, all of which potentially have different triggers and clinical presentations. Asthma can be episodic or can follow a relapsing and remitting course, which further complicates attempts to arrive at a diagnosis based on a single patient-physician encounter. Although asthma is a chronic disease, the expected rate of spontaneous remissions of adult asthma and the stability of diagnosis are unknown.

Shawn D. Aaron, M.D., of the Ottawa Hospital Research Institute, University of Ottawa, Canada, and colleagues conducted a study that included 701 adults who reported a history of physician-diagnosed asthma established within the past five years. All participants were assessed with home peak flow and symptom monitoring, spirometry (measures lung function), and bronchial challenge tests, and those participants using daily asthma medications had their medications gradually tapered off over four study visits. Participants in whom a diagnosis of current asthma was ultimately ruled out were followed up clinically with repeated bronchial challenge tests over one year.

Of 701 participants, 613 completed the study and could be conclusively evaluated for a diagnosis of current asthma, which was ruled out in 203 of 613 study participants (33 percent). Twelve participants (2 percent) were found to have serious cardiorespiratory conditions that had been previously misdiagnosed as asthma in the community. After an additional 12 months of follow-up, 181 participants (30 percent) continued to exhibit no clinical or laboratory evidence of asthma. Participants in whom current asthma was ruled out, compared with those in whom it was confirmed, were less likely to have undergone testing for airflow limitation in the community at the time of initial diagnosis (44 percent vs 56 percent, respectively). More than 90 percent of participants in whom asthma was ruled out had asthma medications safely stopped for an additional one-year period.

"Two phenomena may account for failure to ultimately confirm current asthma in 33.1 percent of the study cohort: (1) spontaneous remission of previously active asthma; and (2) misdiagnosis of asthma in the community. At least 24 of 203 participants (11.8 percent) in whom current asthma was ruled out had undergone pulmonary function tests in the community that had been previously diagnostic of asthma. These participants presumably experienced spontaneous remission of their asthma at some time between their initial community diagnosis and entry into the study," the authors write.

"This study also suggests that misdiagnosis of asthma may occasionally occur in the community. In 2.0 percent of study participants, a serious untreated cardiorespiratory condition was identified that may have been previously misdiagnosed as asthma. In addition, the study demonstrated that failure to consistently use objective testing at the time of initial diagnosis of asthma was associated with failure to confirm current asthma. These results suggest that whenever possible, physicians should order objective tests, such as prebronchodilator and postbronchodilator spirometry, serial peak flow measurements, or bronchial challenge tests, to confirm asthma at the time of initial diagnosis."