—We thank Drs Speizer and Doll for their letter.
They believe that our report "begs the real issue," but we think their comment misses the main point. The key distinction in the diagnostic-exchange hypothesis is that asthma was often underdiagnosed in the days before a response to bronchodilators would help suggest or confirm the diagnosis. After bronchodilators became widely used, the patients with asthma who formerly would have been given a false-negative diagnosis, such as some other respiratory disease, could receive a correct certification of asthma. The autopsy study cited by Speizer and Doll1 simply confirmed that very few of the asthma diagnoses were false-positive in patients who died during the "epidemic." A check for false-positive errors, however, does not address the previous (or concomitant) false-negative diagnoses that are a prime source of the diagnostic-exchange problem. We would have hoped that "the science of the practice of common sense"