Credibility of a smoking questionnaire based on urine cotinine level for patients with bladder cancer - a preliminary report.

An analysis of the reliability of a questionnaire on smoking in 96 patients with transitional cell carcinoma (TCC) of the bladder. The credibility of the questionnaire was evaluated based on the detection of cotinine, an objective marker of tobacco smoke exposure, in urine. It was confirmed that approximately 18% of smokers did not admit to smoking, did not comply with recommendations to stop smoking, and about 4% of non-smokers were exposed to tobacco smoke unknowingly.