title: COPD Diagnostic Questionnaire (CDQ) for selecting at-risk patients for spirometry: a cross-sectional study in Australian general practice.
abstract: BACKGROUND
  Using the COPD Diagnostic Questionnaire (CDQ) as a selection tool for spirometry could potentially improve the efficiency and accuracy of chronic obstructive pulmonary disease (COPD) diagnosis in at-risk patients.
  
  
  OBJECTIVE
  To identify an optimal single cut point for the CDQ that divides primary care patients into low or high likelihood of COPD, with the latter group undergoing spirometry.
  
  
  METHODS
  Former or current smokers aged 40-85 years with no prior COPD diagnosis were invited to a case-finding appointment with the practice nurse at various general practices in Sydney, Australia. The CDQ was collected and pre- and post-bronchodilator spirometry was performed. Cases with complete CDQ data and spirometry meeting quality standards were analysed (1,054 out of 1,631 patients). CDQ cut points were selected from a receiver operating characteristic (ROC) curve.
  
  
  RESULTS
  The area under the ROC curve was 0.713. A cut point of 19.5 had the optimal combination of sensitivity (63%) and specificity (70%) with two-thirds below this cut point. A cut point of 14.5 corresponded to a sensitivity of 91%, specificity of 35% and negative predictive value of 96%, and 31% of patients below this cut point.
  
  
  CONCLUSIONS
  The CDQ can be used to select patients at risk of COPD for spirometry using one cut point. We consider two possible cut points. The 19.5 cut point excludes a higher proportion of patients from undergoing spirometry with the trade-off of more false negatives. The 14.5 cut point has a high sensitivity and negative predictive value, includes more potential COPD cases but has a higher rate of false positives.
authors.affiliation: School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Stanley
authors.affiliation: Centre for Health Equity Training Research and Evaluation (CHETRE), Ingham Institute, Liverpool BC, New South Wales, Australia.
authors.forename: Iqbal
authors.initials: I
authors.lastname: Hasan
authors.affiliation: 1] School of Health, University of South Australia, Adelaide, South Australia, Australia [2] Discipline of General Practice, School of Population Health, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Crockett
authors.affiliation: Department of General Practice, CAHPRI School for Public Health and Care, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Onno C P
authors.initials: OC
authors.lastname: van Schayck
authors.affiliation: School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Zwar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001315:Australia / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013147:Spirometry / Q000379:methods*; D011795:Surveys and Questionnaires