Sir

Your News story 'Alzheimer's tests under fire' (Nature 455, 1155; 2008) highlights the fierce debate about the availability of genetic tests to the general public. The overwhelming amount of data concerning the major genetic risk factors for Alzheimer's disease have recently been summarized: they show that various markers, although promising, are far from conclusive and are much farther from mainstream use than the controversial APOE test (L. Bertram and R. E. Tanzi Nature Rev. Neurosci. 9, 768–778; 2008), whose flaws you describe.

During our 15 years of studying genetic risk factors for Alzheimer's disease (see J. R. M. Oliveira et al. J. Mol. Neurosci. doi 10.1007/s12031-008-9124-0; 2008), our group has often been approached by private laboratories and colleagues interested in making APOE genotyping — and many other markers — available to the general public.

In our experience, non-affected family members are often interested in knowing their genotype, in the hope of preventing the disorder. But laypeople are rarely well equipped to understand the often murky relationship between their genotype and phenotype. They may reach erroneous conclusions, make irresponsible lifestyle decisions or pursue unproven therapies if their test results seem alarming.

The core of the problem is a misunderstanding of crucial terms such as risk factor, prevention, cure and treatment, along with the false notion that medication is available to prevent the manifestation of symptoms. People who become aware of their genetic risk factors through a test with limited predictive power will be forced to grapple with a complex set of uncertainties. That is not a responsible way to offer medical information.