title: Pulmonary function testing in New Zealand: the use and importance of reference ranges.
abstract: OBJECTIVE
  The diagnosis, assessment and management of a wide range of respiratory diseases rely on accurate interpretation of lung function tests through the use of reference equations to generate predicted values. This paper ascertains the suitability of reference equations currently used in New Zealand through comparison with newly derived equations from the Wellington Respiratory Survey, and discusses the relevance of the findings to the Asia Pacific region.
  
  
  METHODS
  A survey of lung function testing facilities determined the reference equations in common usage. Pulmonary function test results from healthy, lifelong non-smoking subjects (n = 180) were expressed as percentage predicted values, with comparisons made between the currently used and Wellington Respiratory Survey reference equations. Differences in disease severity classification in subjects with COPD (n = 46) and asthma (n = 61) were determined, using the different reference equations.
  
  
  RESULTS
  Currently used equations significantly underpredict measured values for FEV(1), PEF, TLC and RV by up to 20%. Severity classification of COPD and asthma based on per cent predicted FEV(1) was substantially altered by the choice of reference equation.
  
  
  CONCLUSIONS
  Many reference equations in current usage in New Zealand are no longer suitable for use. The applicability of reference equations used in other populations and countries within the Asia Pacific region requires further investigation. We recommend that up-to-date reference equations are derived and implemented if those currently used are shown to be unsatisfactory.
authors.affiliation: Medical Research Institute of New Zealand, Wellington, New Zealand.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Marsh
authors.forename: Sarah
authors.initials: S
authors.lastname: Aldington
authors.forename: Mathew V
authors.initials: MV
authors.lastname: Williams
authors.forename: Mark
authors.initials: M
authors.lastname: Weatherall
authors.forename: David
authors.initials: D
authors.lastname: Robiony-Rogers
authors.forename: David
authors.initials: D
authors.lastname: Jones
authors.forename: Richard
authors.initials: R
authors.lastname: Beasley
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006306:Health Surveys; D006801:Humans; D008168:Lung / Q000502:physiology / Q000503:physiopathology; D008171:Lung Diseases / Q000145:classification / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009520:New Zealand; D011237:Predictive Value of Tests; D012016:Reference Values; D012129:Respiratory Function Tests / Q000379:methods*; D012720:Severity of Illness Index; D013147:Spirometry