Pairwise t-tests comparing heterozygotes and homozygotes of the CYP2A6 alleles *1B, *1D, *1H and *14 provide no evidence for a significant difference between diplotypes composed of these haplotypes (Table 4, Fig. 1). Testing by ANOVA found no evidence that any of these diplotypes are different from one another (df=7, p=0.46). These four haplotypes are hence termed ‘normal metabolizer’ haplotypes. By comparison, carriers of the *1A(51A) or *9 haplotypes display significantly slower nicotine metabolism than carriers of normal metabolizer haplotypes, and significantly faster metabolism efficiency than diplotypes consisting of likely null alleles (*2, *4 and *12) (Table 4, Fig 2).
