Error in smoking measures: effects of intervention on relations of cotinine and carbon monoxide to self-reported smoking. The Lung Health Study Research Group

Am J Public Health. 1993 Sep;83(9):1251-7. doi: 10.2105/ajph.83.9.1251.


Objectives: Sources of measurement error in assessing smoking status are examined.

Methods: The Lung Health Study, a randomized trial in 10 clinical centers, includes 3923 participants in a smoking cessation program and 1964 usual care participants. Smoking at first annual follow-up was assessed by salivary cotinine, expired air carbon monoxide, and self-report. Each of these measures is known to contain some error. Sensitivity and specificity were calculated by comparing a biochemical measure with self-report to produce an undifferentiated estimate of error. Classification error rates due to imprecision of the biochemical measures and to the error in self-report were estimated separately.

Results: For cotinine compared with self-report, the sensitivity was 99.0% and the specificity 91.5%. For carbon monoxide compared with self-report, the sensitivity was 93.7% and the specificity 87.2%. The classification error attributed to self-report, estimated by comparing the results from intervention and control groups, was associated with the responses of 3% and 5% of participants, indicating a small but significant bias toward a socially desirable response.

Conclusions: In absolute terms in these data, both types of error were small.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Breath Tests
  • Carbon Monoxide / analysis*
  • Cotinine / analysis*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Saliva / chemistry*
  • Self Disclosure*
  • Sensitivity and Specificity
  • Smoking Cessation
  • Smoking* / psychology


  • Carbon Monoxide
  • Cotinine