smokers (mean≈170 ng/mL) (26). Previous studies in the CHRNA5-A3-B4 field have suggested objective biomarkers are more sensitive than CPD (7). We have previously shown that CHRNA5-A3-B4 variants are significantly associated with cotinine levels in as few as 163 smokers (12). Therefore, we believe that the accuracy of biomarkers (versus self-report CPD) compensates for the smaller size of our study.
