Assessment of peak expiratory flow in asthma.

Assessment of peak expiratory flow is a test of airway caliber that is simple, inexpensive, and easily performed on an outpatient basis. Because asthma is characterized by fluctuations in airway caliber, such a test can be useful in the diagnosis and assessment of the condition's severity. Although this approach is useful, it has several pitfalls: peak expiratory flow is less sensitive than forced expiratory volume in 1 second in the assessment of airway caliber; compliance with daily assessment on a long-term basis is generally not satisfactory; and daily monitoring of airway caliber may not be more sensitive than symptoms recorded in a diary to identify flare-ups. Peak expiratory flow may be a useful means of asthma assessment for subjects who either under- or over-estimate their symptoms, if the tests are conducted over short intervals of monitoring, and specifically in the investigation of occupational asthma.