title: Comparison between objective measures of smoking and self-reported smoking status in patients with asthma or COPD: are our patients telling us the truth?
abstract: OBJECTIVE
  Smoking prevalence is frequently estimated on the basis of self-reported smoking status. That can lead to an underestimation of smoking rates. The aim of this study was to evaluate the difference between self-reported smoking status and that determined through the use of objective measures of smoking at a pulmonary outpatient clinic.
  
  
  METHODS
  This was a cross-sectional study involving 144 individuals: 51 asthma patients, 53 COPD patients, 20 current smokers, and 20 never-smokers. Smoking status was determined on the basis of self-reports obtained in interviews, as well as through tests of exhaled carbon monoxide (eCO) and urinary cotinine.
  
  
  RESULTS
  All of the asthma patients and COPD patients declared they were not current smokers. In the COPD and asthma patients, the median urinary cotinine concentration was 167 ng/mL (range, 2-5,348 ng/mL) and 47 ng/mL (range, 5-2,735 ng/mL), respectively (p < 0.0001), whereas the median eCO level was 8 ppm (range, 0-31 ppm) and 5 ppm (range, 2-45 ppm), respectively (p < 0.05). In 40 (38%) of the patients with asthma or COPD (n = 104), there was disagreement between the self-reported smoking status and that determined on the basis of the urinary cotinine concentration, a concentration > 200 ng/mL being considered indicative of current smoking. In 48 (46%) of those 104 patients, the self-reported non-smoking status was refuted by an eCO level > 6 ppm, which is also considered indicative of current smoking. In 30 (29%) of the patients with asthma or COPD, the urinary cotinine concentration and the eCO level both belied the patient claims of not being current smokers.
  
  
  CONCLUSIONS
  Our findings suggest that high proportions of smoking pulmonary patients with lung disease falsely declare themselves to be nonsmokers. The accurate classification of smoking status is pivotal to the treatment of lung diseases. Objective measures of smoking could be helpful in improving clinical management and counseling.
authors.affiliation: University of São Paulo, School of Medicine, Hospital das Clínicas, São Paulo, Brazil. Department of Pulmonology, Instituto do Coração - InCor, Heart Institute - University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, Brazil.
authors.forename: Rafael
authors.initials: R
authors.lastname: Stelmach
authors.affiliation: University of São Paulo, School of Medicine, Hospital das Clínicas, São Paulo, Brazil. Department of Pulmonology, Instituto do Coração - InCor, Heart Institute - University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, Brazil.
authors.forename: Frederico Leon Arrabal
authors.initials: FL
authors.lastname: Fernandes
authors.affiliation: University of São Paulo, School of Medicine, Hospital das Clínicas, São Paulo, Brazil. Department of Pulmonology, Instituto do Coração - InCor, Heart Institute - University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, Brazil.
authors.forename: Regina Maria
authors.initials: RM
authors.lastname: Carvalho-Pinto
authors.affiliation: University of São Paulo, School of Medicine, Hospital das Clínicas, São Paulo, Brazil. Department of Pulmonology, Instituto do Coração - InCor, Heart Institute - University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, Brazil.
authors.forename: Rodrigo Abensur
authors.initials: RA
authors.lastname: Athanazio
authors.affiliation: University of São Paulo, School of Medicine, Hospital das Clínicas, São Paulo, Brazil. Department of Pulmonology, Instituto do Coração - InCor, Heart Institute - University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, Brazil.
authors.forename: Samia Zahi
authors.initials: SZ
authors.lastname: Rached
authors.affiliation: University of São Paulo, School of Medicine, Hospital das Clínicas, São Paulo, Brazil. Department of Pulmonology, Instituto do Coração - InCor, Heart Institute - University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, Brazil.
authors.forename: Gustavo Faibischew
authors.initials: GF
authors.lastname: Prado
authors.affiliation: University of São Paulo, School of Medicine, Hospital das Clínicas, São Paulo, Brazil. Department of Pulmonology, Instituto do Coração - InCor, Heart Institute - University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, Brazil.
authors.forename: Alberto
authors.initials: A
authors.lastname: Cukier
mesh_terms: D001249:Asthma / Q000453:epidemiology* / Q000652:urine; D015415:Biomarkers / Q000032:analysis; D001938:Brazil / Q000453:epidemiology; D002248:Carbon Monoxide / Q000032:analysis; D003367:Cotinine / Q000652:urine; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology* / Q000378:metabolism; D057566:Self Report; D012907:Smoking / Q000453:epidemiology* / Q000652:urine
chemical_list: D015415:Biomarkers; D002248:Carbon Monoxide; D003367:Cotinine
keywords: Asthma; Carbon monoxide; Cotinine; Pulmonary disease, chronic obstructive; Smoking