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

Aims Previous studies have suggested that the self-reporting of smoking amo ngst diabetic patients is unreliable, and that objective markers such as br eath carbon monoxide (CO) or urinary cotinine are needed. As these studies have been mostly in young Type 1 diabetic patients, the reliability of smok ing history has been assessed in a large group of older Type 2 diabetic pat ients. Methods Two hundred and ninety-nine Type 2 diabetic patients were investiga ted for smoking habits by unstructured questionnaire, breath CO, and urinar y ratio. Results Mean age of the group was 63 (range 30-80) years and 41% were femal e. Direct questioning suggested 77 (26%) to be smokers, and of these 852 ha d raised (>1 mu g/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 questionnai re 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 diabe tic patients, a structured smoking: history appeared to identify current sm okers with goad accuracy.