Unrelated African American (N = 52), Asian American (N = 55), and European American ancestry individuals (N = 239) from three existing laboratory-based nicotine metabolism studies were selected for genotyping on the Smokescreen array [57]. For all samples, the NMR is defined as the trans-3’-hydroxycotinine to cotinine ratio. In these three studies, biospecimens were collected, and creatinine-adjusted cotinine and trans-3’-hydroxycotinine levels were estimated via mass spectrometry using an established method [57].
