Comparison of questionnaire, breath carbon monoxide and urine cotinine in assessing the smoking habits of Type 2 diabetic patients

Summary Aims Previous studies have suggested that the self-reporting of smoking amongst diabetic patients is unreliable, and that objective markers such as breath carbon monoxide (CO) or urinary cotinine are needed. As these studies have been mostly in young Type 1 diabetic patients, the reliability of smoking history has been assessed in a large group of older Type 2 diabetic patients. Methods Two hundred and ninety-nine Type 2 diabetic patients were investigated for smoking habits by unstructured questionnaire, breath CO, and urinary ratio. Results Mean age of the group was 63 (range 30–80) years and 41% were female. Direct questioning suggested 77 (26%) to be smokers, and of these 852 had raised (> 1 μg/mg) urinary cotinine–creatinine , and 71% raised (> 8 p.p.m.) breath CO. Assuming urinary cotinine–creatinine as the ‘gold standard’, the sensitivity, specificity and positive predictive values for questionnaire were 97%, 95% and 85%, respectively; and for breath CO they were 74%, 98%, and 93%. Conclusion It is concluded that at least in this population of Type 2 diabetic patients, a structured smoking history appeared to identify current smokers with good accuracy.