Blood cotinine levels as indicators of smoking treatment outcome.

Pretreatment blood cotinine levels, expired carbon monoxide levels, and self-reported cigarette consumption were evaluated as predictors of smoking treatment outcome in 114 patients. Of these indices of nicotine intake, blood cotinine level was the most useful predictor. High blood cotinine level was the best predictor of dropping out before completion of treatment and of smoking at the end of treatment and at follow-ups. The usefulness of cotinine as a marker of tobacco dependence is discussed.