Validation of self-reported smoking status by simultaneous measurement of carbon monoxide and salivary thiocyanate

Objective. The objective of this study was to determine the validity of tob acco questionnaires when using as gold standard either a single biomarker o r a combination of two biomarkers. Methods. The methods were self-reported smoking compared with salivary thio cyanate and expired carbon monoxide in a 1996, population-based, Swiss surv ey of 552 men and 565 women. Results. Sensitivity of self-reported smoking relative to salivary thiocyna te or carbon monoxide alone was low (38.2% for salivary thiocyanate greater than or equal to 100 mg/L, 56.4% for salivary thiocyanate greater than or equal to 150 mg/L and 62.6% for carbon monoxide greater than or equal to 9 ppm). When defining true positive smokers as people with high concentration of both salivary thiocyanate and carbon monoxide, overall, sensitivity was 88.6% and specificity was 87.2%. In women, sensitivity increased from 85 t o 89% when removing subjects exposed to passive smoking. When excluding hea vy smokers, sensitivity decreased to 63% in men and to 71% in women. Older women had tendency to misreport smoking. Conclusions. This comparison of questionnaire data with the simultaneous me asurement of salivary thiocyanate and expired carbon monoxide indicates tha t valid responses can be obtained for self-reported, current smoking in pop ulation-based surveys. However, the validity of questionnaires can be under estimated if the gold standard (of exposure to tobacco smoke) is either hig h levels of carbon monoxide or high levels of salivary thiocyanate, (C) 200 0 American Health Foundation and Academic Press.