Thanks for reading the Spittoon. We’re not planning to do a post like that, but I can say a few words about the difficulties of genotyping the SNP that determines APOE status (rs429358).

Some parts of the genome are especially difficult to read due to the sequence and/or structure of the DNA molecule in those regions. As luck would have it, that’s the case with the part of chromosome 19 near rs429358.

There are ways to genotype rs429358 by zeroing in on it specifically. But our genotyping platform is optimized to provide accurate results at more than 500,000 locations across the genome, not at any one location in particular.

We can make an educated guess about a person’s genotype at rs429358 based on the data we do collect, and get the correct result in the majority of cases. But our goal is to provide accurate genetic information for everyone across the genome; we want to have near-perfect genotyping for rs429358 before we start giving customers their APOE results. We expect to be able to do that soon.

It could be interesting to have a more detailed blog post about what “technical reasons” prevent you from giving out APOE status, what solutions are possible, why that particular SNP is more problematic to sequence than others, etc.