Variability of peak expiratory flow in an unselected sample of school children

: In the framework of an epidemiological study, the information by peak flow variability (PEFV) was compared to the history of asthma in a non-selected population of primary-school children (n = 1812). PEFV as assessed by twice daily recordings of PEF for a one week period (n = 1237) was calculated as average of daily amplitudes (AVAM: average amplitude mean) in the case of at least complete data for five days (n = 991). Elevated PEFV defined as AVAM > 12%, was cross-tabulated with the asthma history (self-administered questionnaire). The median (90%-confidence-interval) of AVAM is 6.3% (2.2-15.9%). In 11.2% (n = 111) of the population, AVAM > 12% occurred). The sensitivity of AVAM > 12% with regard to "doctor's diagnosed asthma" (n = 35) is 37%. Under exclusion of children with recurrent wheezy bronchitis a specificity for AVAM > 12% of 90% is found. Our data on primary-school children suggests that PEFV is a specific but only slightly sensitive measurement with regard to previously diagnosed bronchial asthma.