at all relevant nucleotides (Table 1). This model requires seven CYP2A6 polymorphisms including the deletion variant, and predicts phenotype in our sample with an R2 of 0.719. Inclusion of gender and smoking status as variables reduces the adjusted R2 marginally to 0.708, indicating the relative instability of gender and smoking status to predict metabolism in our sample. The phenotype can be predicted from the model by the equation, phenotype = 1 − (intercept • haplotype1 • haplotype2), using the parameter estimates summarized in Table 7. The estimate for the intercept is primarily driven by the three assumed null homozygotes, although the fitted parameter is based on the entire data set. The intercept represents the contribution of all other activities converting nicotine to cotinine following oral administration not accounted for by CYP2A6 (Table 7).
