I think David is right. Because the general chance of AS is so low, and the relative risk factors for most of the SNPs reported for AS in Promethease are between 0.7 - 1.5, I don't think they would be of any diagnostic value.
However the 20x relative risk rs7743761(A;A) allele could be an exception since it's a high odds ratio and only a very small percentage of people have that allele - looks like about 2% of Europeans from the Promethease graph.
These are the two studies that are linked to as references in Promethease for that SNP:
The first one mentions rs7743761 but I couldn't find any mention of a 20x odds ratio or see anything like that in the tables or figures. The second one doesn't seem to mention rs7743761 at all. So perhaps Promethease made an error in their reporting on that SNP.