Am. J. Respir. Crit. Care Med.,
Volume 160, Number 2, August 1999, 427-434
Peak Flow Variability in the SAPALDIA Study and Its
Validity in Screening for Asthma-related Conditions
NINO
KÜNZLI,
ELISABETH ZEMP
STUTZ,
ANDRE P.
PERRUCHOUD,
OTTO
BRÄNDLI,
JEAN-MARIE
TSCHOPP,
GIANFRANCO
BOLOGNINI,
WERNER
KARRER,
CHRISTIAN
SCHINDLER,
URSULA
ACKERMANN-LIEBRICH,
and
PHILIPPE
LEUENBERGER, for the SAPALDIATeam
Swiss Study on Air Pollution and Lung Disease in Adults (SAPALDIA); Institute of Social and Preventive Medicine, University of Basel, Basel;
Centre Valaisan de Pneumologie, Montana; Zürcher Höhenklinik, Wald; Ospedale Mendrisio, Mendrisio; Luzerner Höhenklinik, Montana;
University Hospital Basel, Basel; and Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
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 (PEFvar) (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 PEFvar as a potential tool with which to screen for asthma. Alternatively, subjects with a PEFvar 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 PEFvar was 4.5%. Among asthmatic subjects, women had nonsignificantly higher PEFvar values
than did men. In all other groups, women had significantly lower PEFvar. Both in the entire population and in subgroups with a higher pretest probability for asthma-related conditions, screening performance of PEF was limited. A PEFvar 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%). PEFvar, 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
PEFvar distributions across subgroups is large.
