Cotinine levels confirmed the classification of participants as nonsmokers (ie, never smokers and former smokers) and current smokers (Table 2), based on conventional indicative cotinine levels among nonsmokers and current smokers (never smokers and former smokers, approximately 5 nmol/L; current smokers, >85 nmol/L) (47). Across all six studies, median cotinine levels for nonsmokers were 3.40 nmol/L or lower (ranging from 0.57 to 3.40 nmol/L), whereas median cotinine levels in current smokers were 968.5 nmol/L or higher (ranging from 968.5 to 1535.0 nmol/L). As described previously, cotinine levels in current smokers in the EPIC study differed between case subjects and control subjects and were therefore considered separately.
