The prevalence of self-reported smoking and validation with urinary cotinine among commercial drivers in major parks in Lagos, Nigeria

The validity of self-reported smoking is questionable because smokers are inclined to deny smoking. We aimed to determine the prevalence of self-reported smoking among intra-city commercial drivers in Lagos, and assess its validity based on urinary cotinine assessment. This study was conducted at three major motor parks in Lagos, Nigeria. Information on smoking status and habits was obtained from 500 consecutive male drivers using a structured questionnaire during a face-to-face interview. Eighty-one self-reported smokers and non-smokers were selected by systematic random sampling for urinary cotinine assessment using cotinine strips. The prevalence of self-reported smoking was compared to the prevalence of smoking based on urinary cotinine and the specificity and positive predictive values of self-reported smoking was determined. Prevalence of self-reported current smoking was 32% and 17.9% of nonsmokers were passive smokers. Among 81 drivers in whom urinary cotinine assessment was performed, the prevalence of smoking based on self-report was 34 (42%) compared to 41 (50.6%) when based on urinary cotinine, (X²=38.56, P<0.001). The rate of misclassification among self-reported non-smokers as smokers was 21.3% and misclassification rate for self-reported smokers as non-smokers was 8.8%. The sensitivity of self-reported smoking in accurately classifying smoking status was 91.2% and the specificity was 78.7%. The prevalence of self-reported cigarette smoking among commercial drivers in Lagos is high and a significant proportion of self-reported non-smokers are passive smokers. Self-reported smoking status obtained during face-to-face interview appears unreliable in obtaining accurate smoking data in our locality.