Clinical methods for the longitudinal study of asthma

Clinical variables used to estimate the severity of asthma, such as the patient's history, physical examination, maximal expiratory flow rates, and a record of treatments needed, appear to be associated statistically. A combination of (a) the patient's personal account of his condition during a week, which provides a record of continuity, and (b) the determination of maximal expiratory flow which objectively records changes in respiratory function, was found to provide a highly reliable index of change, i.e., positive or negative “improvement.” None of the procedures evaluated could be considered unrelated to “improvement” and therefore be discarded. While it may be desirable to include other types of information in scoring the severity of asthma, or to obtain more frequent recording of data, weekly records (graded numerically) of history, physical examination, maximal expiratory flow rate, and treatments received are useful and sensitive indices of change in longitudinal studies.