Abstract
As genetic tests become cheaper and more readily available, pressure is increasing to routinely test individuals for susceptibility genes for complex common disorders. Using Alzheimer’s disease (AD) as an illustrative example, it is shown how population databases of AD cases on which individual risk estimates are based are faulty due to confusion about the AD phenotype. Furthermore, the APOEe4 genotype associated with increased risk of AD is neither necessary nor sufficient to cause AD. The article concludes with ethnographic findings that result from interviews with individuals who have been tested for their APOE status.