title: A discriminant function model as an alternative method to spirometry for COPD screening in primary care settings in China.
abstract: OBJECTIVE
  COPD is often underdiagnosed in a primary care setting where the spirometry is unavailable. This study was aimed to develop a simple, economical and applicable model for COPD screening in those settings.
  
  
  METHODS
  First we established a discriminant function model based on Bayes' Rule by stepwise discriminant analysis, using the data from 243 COPD patients and 112 non-COPD subjects from our COPD survey in urban and rural communities and local primary care settings in Guangdong Province, China. We then used this model to discriminate COPD in additional 150 subjects (50 non-COPD and 100 COPD ones) who had been recruited by the same methods as used to have established the model. All participants completed pre- and post-bronchodilator spirometry and questionnaires. COPD was diagnosed according to the Global Initiative for Chronic Obstructive Lung Disease criteria. The sensitivity and specificity of the discriminant function model was assessed.
  
  
  RESULTS
  THE ESTABLISHED DISCRIMINANT FUNCTION MODEL INCLUDED NINE VARIABLES: age, gender, smoking index, body mass index, occupational exposure, living environment, wheezing, cough and dyspnoea. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, accuracy and error rate of the function model to discriminate COPD were 89.00%, 82.00%, 4.94, 0.13, 86.66% and 13.34%, respectively. The accuracy and Kappa value of the function model to predict COPD stages were 70% and 0.61 (95% CI, 0.50 to 0.71).
  
  
  CONCLUSIONS
  This discriminant function model may be used for COPD screening in primary care settings in China as an alternative option instead of spirometry.
authors.affiliation: State Key Laboratory of Respiratory Diseases, Guangzhou Institute of Respiratory Diseases, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, China;
authors.forename: Jiangyu
authors.initials: J
authors.lastname: Cui
authors.forename: Yumin
authors.initials: Y
authors.lastname: Zhou
authors.forename: Jia
authors.initials: J
authors.lastname: Tian
authors.forename: Xinwang
authors.initials: X
authors.lastname: Wang
authors.forename: Jingping
authors.initials: J
authors.lastname: Zheng
authors.forename: Nanshan
authors.initials: N
authors.lastname: Zhong
authors.forename: Pixin
authors.initials: P
authors.lastname: Ran