Association between lower respiratory tract symptoms and falls in peak expiratory flow in children.

Peak expiratory flow (PEF) measurements are increasingly recommended in childhood asthma management. However, few data are available on the temporal relationship between the onset of upper and lower respiratory tract symptoms and significant falls in PEF. We wanted to determine whether falls in PEF constitute a sensitive marker for clinical episodes of respiratory morbidity. We therefore analysed data on daily PEF and respiratory symptom recording from a 12 month longitudinal study in 192 children aged 7 and 8 yrs with current respiratory symptoms. Outcome measures were number of and relationship between: 1) episodes of fall in PEF (defined as a fall in PEF for more than 2 days to < 1.5 SD below individual mean morning PEF); and 2) upper and lower respiratory tract symptom events (defined as a respiratory symptoms score of > 3 units within three consecutive days). One hundred and eight six of the 192 children completed the study. For the group as a whole, the mean number of PEF episodes per subject was 3.5, and the mean number of symptom events 8.9, with 29% of symptom events being temporally associated with a PEF episode, and 40% of PEF episodes not being accompanied by a symptom event. Forty nine percent of PEF episodes were preceded by at least two consecutive days of either upper or lower respiratory symptoms. We conclude that falls in PEF alone were not a sensitive marker for episodes of respiratory morbidity. On almost half of the occasions where PEF did fall, morbidity could have been detected at least 2 days earlier using symptom reporting.(ABSTRACT TRUNCATED AT 250 WORDS)