title: FEV3, FEV6 and their derivatives for detecting airflow obstruction in adult Chinese.
abstract: BACKGROUND
  Forced expiratory volume in 3 seconds (FEV(3)) and 6 seconds (FEV(6)) could complement FEV(1) and forced vital capacity (FVC) for detecting airflow obstruction.
  
  
  OBJECTIVE
  To compare FEV(1)/ FEV(6) and FEV(3)/FVC with  FEV(1)/FVC in the detection of airflow obstruction.
  
  
  METHODS
  Previous lung function data were re-analysed to establish reference values for FEV(3) and FEV(6). Data from a separate cohort of male smokers were used as test set. FEV(1), FEV(3),  FEV(6), FVC, FEV(1)/FVC, FEV(1)/ FEV(6) and FEV(3)/FVC were regressed against age, standing height, weight and body mass index, and the mean and 95% confidence intervals for the lower limit of normal (LLN) values for these parameters were determined.
  
  
  RESULTS
  The percentage of smokers with airflow obstruction in the test population using FEV(1)/FVC < LLN was 15.0%, while using FEV(1)/ FEV(6) < LLN and FEV(3)/FVC < LLN they were respectively 18.5% and 18.1%. Using FEV(1)/FVC < LLN as reference,  the sensitivity and specificity of FEV(1)/ FEV(6) < LLN in identifying airflow obstruction were 82.3% and 92.8%, while those for FEV(3)/FVC < LLN were 78.5% and 92.6%; the positive and negative predictive values were 67% and 96.7% for FEV(1)/ FEV(6)  < LLN and 65.3% and 96% for FEV(3)/FVC < LLN.
  
  
  CONCLUSIONS
  FEV(3)/FVC < LLN and FEV(1)/ FEV(6) < LLN are comparable to FEV(1)/FVC < LLN for detecting airflow obstruction. FEV(3)/FVC < LLN could be useful in screening  for airflow obstruction, while FEV(1)/ FEV(6) < LLN is useful in detecting airflow limitation in the elderly or in subjects with severe airflow obstruction.
authors.affiliation: Department of Medicine, University of Hong Kong, Hong Kong, China.
authors.forename: D C L
authors.initials: DC
authors.lastname: Lam
authors.forename: D Y T
authors.initials: DY
authors.lastname: Fong
authors.forename: W C
authors.initials: WC
authors.lastname: Yu
authors.forename: F W S
authors.initials: FW
authors.lastname: Ko
authors.forename: A C W
authors.initials: AC
authors.lastname: Lau
authors.forename: J W M
authors.initials: JW
authors.lastname: Chan
authors.forename: K L
authors.initials: KL
authors.lastname: Choo
authors.forename: T Y W
authors.initials: TY
authors.lastname: Mok
authors.forename: C Y
authors.initials: CY
authors.lastname: Tam
authors.forename: M S M
authors.initials: MS
authors.lastname: Ip
authors.forename: M M W
authors.initials: MM
authors.lastname: Chan-Yeung
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000402:Airway Obstruction / Q000175:diagnosis* / Q000473:pathology; D002681:China; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012016:Reference Values; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D013997:Time Factors; D014797:Vital Capacity; D055815:Young Adult