title: Peak flow variability in the SAPALDIA study and its validity in screening for asthma-related conditions. The SPALDIA Team.
abstract: We used 3-wk peak expiratory flow (PEF) measurements (twice daily) made in the diary study of the population-based Swiss Study on Air Pollution and Lung Disease in Adults to describe PEF-variability (PEF(var)) (amplitude as a percent of the mean, PEF [i.e., difference between morning and evening values divided by the mean]) in the study population and in five subgroups (physician-diagnosed asthma; current asthma, or physician-diagnosed asthma plus asthma attacks and/or medication; history of wheezing without a cold; hyperreactive; and nonsymptomatic). We assessed the performance of PEF(var) as a potential tool with which to screen for asthma. Alternatively, subjects with a PEF(var) of >/= 20%, >/= 30%, and >/= 50% on at least 2 d were considered to have high variability. The analyses were conducted for subgroups with different pretest probabilities for asthma-related conditions. The median PEF(var) was 4.5%. Among asthmatic subjects, women had nonsignificantly higher PEF(var) values than did men. In all other groups, women had significantly lower PEF(var). Both in the entire population and in subgroups with a higher pretest probability for asthma-related conditions, screening performance of PEF was limited. A PEF(var) of >/= 20% on at least 2 d detected current asthma with a sensitivity of 36% (specificity = 90%; positive predictive value = 16.4%). Results were better among subjects with a history of wheezing without colds (sensitivity = 40.4%; specificity = 83.6%; positive predictive value = 45.2%). PEF(var), a useful measure both clinically and in epidemiology, is of limited value when unselected populations are screened for asthma-related conditions, since the overlap of PEF(var) distributions across subgroups is large.
authors.affiliation: Swiss Study on Air Pollution and Lung Disease in Adults (SAPALDIA); Institute of Social and Preventive Medicine, University of Basel, Basel, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Künzli
authors.forename: E Z
authors.initials: EZ
authors.lastname: Stutz
authors.forename: A P
authors.initials: AP
authors.lastname: Perruchoud
authors.forename: O
authors.initials: O
authors.lastname: Brändli
authors.forename: J M
authors.initials: JM
authors.lastname: Tschopp
authors.forename: G
authors.initials: G
authors.lastname: Bolognini
authors.forename: W
authors.initials: W
authors.lastname: Karrer
authors.forename: C
authors.initials: C
authors.lastname: Schindler
authors.forename: U
authors.initials: U
authors.lastname: Ackermann-Liebrich
authors.forename: P
authors.initials: P
authors.lastname: Leuenberger
mesh_terms: D000293:Adolescent; D000328:Adult; D000397:Air Pollution / Q000009:adverse effects*; D001249:Asthma / Q000175:diagnosis* / Q000453:epidemiology; D002940:Circadian Rhythm; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate / Q000187:drug effects; D011159:Population Surveillance; D011237:Predictive Value of Tests; D012307:Risk Factors; D013557:Switzerland / Q000453:epidemiology