title: Accuracy and precision of desktop spirometers in general practices.
abstract: BACKGROUND
  Spirometry has become an essential tool for general practices to diagnose and monitor chronic airways diseases, but very little is known about the performance of the spirometry equipment that is being used in general practice settings. The use of invalid spirometry equipment may have consequences on disease diagnosis and management of patients.
  
  
  OBJECTIVE
  To establish the accuracy and precision of desktop spirometers that are routinely used in general practices.
  
  
  METHODS
  We evaluated a random sample of 50 spirometers from Dutch general practices by testing them on a certified waveform generator using 8 standard American Thoracic Society waveforms to determine accuracy and precision. Details about the brand and type of spirometers, year of purchase, frequency of use, cleaning and calibration were inquired with a study-specific questionnaire.
  
  
  RESULTS
  39 devices (80%) were turbine spirometers, 8 (16%) were pneumotachographs, and 1 (2%) was a volume displacement spirometer. Mean age of the spirometers was 4.3 (SD 3.7) years. Average deviation from the waveform generator reference values (accuracy) was 25 ml (95% confidence interval 12-39 ml) for FEV(1) and 27 ml (10-45 ml) for FVC, but some devices showed substantial deviations. FEV(1) deviations were larger for pneumotachographs than for turbine spirometers (p < 0.0031), but FVC deviations did not differ between the two types of spirometers. In the subset of turbine spirometers, no association between age and device performance was observed.
  
  
  CONCLUSIONS
  On average, desktop spirometers in general practices slightly overestimated FEV(1) and FVC values, but some devices showed substantial deviations. General practices should pay more attention to the calibration of their spirometer.
authors.affiliation: COPD and Asthma Research and Development Unit, Department of Primary and Community Care, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Tjard R J
authors.initials: TR
authors.lastname: Schermer
authors.forename: Eddy H A
authors.initials: EH
authors.lastname: Verweij
authors.forename: Riet
authors.initials: R
authors.lastname: Cretier
authors.forename: Annelies
authors.initials: A
authors.lastname: Pellegrino
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Crockett
authors.forename: Patrick J P
authors.initials: PJ
authors.lastname: Poels
mesh_terms: D000704:Analysis of Variance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety; D005541:Forced Expiratory Volume; D058006:General Practice / Q000295:instrumentation* / Q000592:standards; D006801:Humans; D009426:Netherlands; D011656:Pulmonary Emphysema / Q000175:diagnosis; D011786:Quality Control; D012680:Sensitivity and Specificity; D013147:Spirometry / Q000295:instrumentation* / Q000706:statistics & numerical data