title: Serial lung function variability using four portable logging meters.
abstract: OBJECTIVE
  Portable lung function logging meters that allow measurement of peak expiratory flow (PEF) and forced expiratory volume in 1 second (FEV(1)) are useful for the diagnosis and exclusion of asthma. The aim of this study was to investigate the within and between-session variability of PEF and FEV(1) for four logging meters and to determine the sensitivity of meters to detect FEV(1) and PEF diurnal changes.
  
  
  METHODS
  Thirteen assessors (all hospital staff members) were asked to record 1 week of 2-hour PEF and FEV(1) measurements using four portable lung function meters. Within-session variability of PEF and FEV(1) were compared for each meter using a coefficient of variation (COV). Between-session variability was quantified using parameter estimates from a cosinor analysis which modeled diurnal change for both lung function measures and also allowed for variation between days for individual sessions.
  
  
  RESULTS
  The mean within-session COV for FEV(1) was consistently lower than that for PEF (p < 0.001). PEF showed a higher but not significantly different (p = 0.068) sensitivity for detecting diurnal variation than FEV(1). PEF was also slightly more variable between days, but not significantly different than FEV(1) (p = 0.409). PEF and FEV(1) diurnal variability did not differ between the 4 meters (p = 0.154 and 0.882 respectively), but within-session FEV(1) COV differed between meters (p = 0.009).
  
  
  CONCLUSIONS
  PEF was marginally more sensitive to within-day variability than FEV(1) but was less repeatable. Overall, differences between the 4 meters were small, suggesting that all meters are clinically useful.
authors.affiliation: Occupational Lung Disease Unit, Department of Respiratory Medicine, Birmingham Heartlands Hospital, Bordesley Green East, Birmingham B9 5SS, UK. vicky.c.moore@heartofengland.nhs.uk
authors.forename: Vicky C
authors.initials: VC
authors.lastname: Moore
authors.forename: Nick R
authors.initials: NR
authors.lastname: Parsons
authors.forename: Maritta S
authors.initials: MS
authors.lastname: Jaakkola
authors.forename: Cedd B S G
authors.initials: CB
authors.lastname: Burge
authors.forename: Charles F
authors.initials: CF
authors.lastname: Pantin
authors.forename: Alastair S
authors.initials: AS
authors.lastname: Robertson
authors.forename: P Sherwood
authors.initials: PS
authors.lastname: Burge
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology; D002940:Circadian Rhythm / Q000502:physiology*; D003627:Data Interpretation, Statistical; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate / Q000502:physiology*; D012680:Sensitivity and Specificity; D013147:Spirometry / Q000295:instrumentation*