Le. Wagenknecht et al., MISCLASSIFICATION OF SMOKING STATUS IN THE CARDIA STUDY - A COMPARISON OF SELF-REPORT WITH SERUM COTININE LEVELS, American journal of public health, 82(1), 1992, pp. 33-36
Background. Although widely used in epidemiological studies, self-repo
rt has been shown to underestimate the prevalence of cigarette smoking
in some populations. Methods. In the CARDIA study, self-report of cig
arette smoking was validated against a biochemical marker of nicotine
uptake, serum cotinine. Results. The prevalence of smoking was slightl
y lower when defined by self-report (30.9%) than when defined by cotin
ine levels equal to or greater than 14 ng/mL (32.2%, P < .05). The mis
classification rate (proportion of reported nonsmokers with cotinine l
evels of at least 14 ng/mL) was 4.2% and was significantly higher amon
g subjects who were Black, had a high school education or less, or wer
e reported former smokers. Possible reasons for misclassification incl
ude reporting error, environmental tobacco smoke, and an inappropriate
cutoff point for delineation of smoking status. Using self-report as
the gold standard, the cotinine cutoff points that maximized sensitivi
ty and specificity were 14, 9, and 15 ng/mL for all, White, and Black
subjects, respectively. The misclassification rate remained significan
tly higher in Black than in White subjects using these race-specific c
riteria. Conclusion. Misclassification of cigarette smoking by self-re
port was low in these young adults; however, within certain race/educa
tion groups, self-report may underestimate smoking prevalence by up to
4%.