Misclassification of smoking habits: An updated review of the literature

Table 5 Factors included in the final model for a rate, with the significant differences in misclassification rates (from base level) by factor level: Cut 1, multivariate analysis

Factor (base level), rates that included the factor in multivariate analysisa		Other factor levels: Difference in rate from base level, significancea
Study type (base level = general population)		Pregnancy	Diseased/case-control
M1	% of self-reported non-smokers whose cotinine implies current smoking		3.92++
M3	% of self-reported ex-smokers whose cotinine implies current smoking	14.63+++	3.89+
M4	% of self-reported current smokers whose cotinine implies non-smoking	-14.24---	10.71++
M7	% of true current smokers who report being ex-smokers		14.74+++
M10	% of self-reported current smokers (plus misclassified non-smokers) who report being ex-smokers		9.11+++
M11	% of true non-smokers who report being current smokers	-2.48-	6.92+++
Age group (base level = young)		Not young	All ages	Not stated
M4	% of self-reported current smokers whose cotinine implies non-smoking	-11.03-	-16.86---	-18.28---
M11	% of true non-smokers who report being current smokers		-3.87---	-4.58--
Time of publication (base level = in 1995 review)		Before 2003	2003 onwards
M4	% of self-reported current smokers whose cotinine implies non-smoking		11.17++
M5	% of true current smokers who report being non-smokers		9.61(+)
M8	% of self-reported current smokers (plus misclassified non-smokers) who report being non-smokers		6.26+
M9	% of self-reported current smokers (plus misclassified non-smokers) who report being never smokers		6.11++
Study quality (base level = good)		Not good
M4	% of self-reported current smokers whose cotinine implies non-smoking	6.32++
Tobacco products considered (baseline level = cigarettes)		Any smoking	Any tobacco
M2	% of self-reported never smokers whose cotinine implies current smoking	-2.22---
M3	% of self-reported ex-smokers whose cotinine implies current smoking	-3.61-
Location in females (base level = Canada/United States)c		Europe	Asia	Other
M5	% of true current smokers who report being non-smokers	6.73(+)	23.61+++
M6	% of true current smokers who report being never smokers	-11.06(-)	27.32++
M8	% of self-reported current smokers (plus misclassified non-smokers) who report being non-smokers		23.19+++
M9	% of self-reported current smokers (plus misclassified non-smokers) who report being never smokers	-8.62-	30.96+++	24.27+b

^aFor each factor, the rates shown are those with which the factor showed a significant (P < 0.01) independent association. All differences shown are adjusted for the other factors significant for that rate. They represent the difference in misclassification rate from the rate for the base level. Only statistically significant differences are shown. The significance of the difference is coded as: ⁺⁺⁺P < 0.001; ^---P < 0.001; ⁺⁺P < 0.01; ^--P < 0.01; ⁺P < 0.05; ^-P < 0.05; ⁽⁺⁾P < 0.1; ^(-)P < 0.1.

^bResult based on three estimates or less.

^cVariations between location were generally not significant for males or for sexes combined - see Supplementary File 3 for full results for sex × location.