libitum 3′-trans-hydroxycotinine/cotinine. That is, parameter estimates for *12 were statistically significantly different from normal function alleles, but not from *2 and *4, whereas estimates for the *9 and *1A(51A) alleles were significantly different from both normal and *2/*4 alleles (data not shown). The designation of *12 is also consistent with recently reported evidence from at least one *12/*2 individual [45]. Our study also benefits from the fortuitous inclusion of two exceptionally slow metabolizing *12 heterozygotes, including one *12/*4 individual, and controls for genotype at rs1137115 (51A/G).
