Table 1—

Criteria for acceptability and reproducibility of maximal expiratory flow/volume curves as stated by the American Thoracic Society (ATS) 3 and European Respiratory Society (ERS) 4

Acceptability
Start-of-test criteria
Vbe%FVC <5% or Vbe <0.15 L, whichever is greater (ATS)
Vbe%FVC <5% or Vbe <0.10 L, whichever is greater (ERS)
End-of-test criteria
 FET >6 (ATS)
 Exhaustion of patient or plateau in time/volume curve (no volume change during 1) (ATS and ERS)
No coughing, Valsalva manoeuvre or hesitation (ATS and ERS)
Reproducibility
 ΔFVC <200 mL and ΔFVC 1 <200 mL (ATS)
 ΔFVC % <5% or ΔFVC <100 mL, whichever is greater and ΔFVC1 % <5% or ΔFVC1 % <100 mL, whichever is greater (ERS)
  • Vbe%FVC: backward extrapolated volume as percentage of forced vital capacity

  • Vbe: backward extrapolated volume

  • FET: forced expiratory time

  • ΔFVC: absolute difference between two highest forced vital capacities

  • ΔFEV1: absolute difference between two highest forced expiratory volumes in one second

  • ΔFVC %: percentage difference between two highest forced vital capacities

  • ΔFVC1 %: percentage difference between two highest forced expiratory volumes in one second