Hi Simply Southern
Over the years I've tried to stay updated with the latest findings regarding AS.
It might be worth contacting the makers of 'Promethase' and asking them to confirm whether or not rs7743761 which apparently corresponds to DHFRP2 (dihydrofolate reductase psi-2) is really associated with increased risk of AS.
Clearly most of the disease risk for AS currently lies within the HLA B27 gene (and to a much lesser extent HLA B40 B51 B47 and B13), followed next by ERAP1 (formerly ARTS1) then IL23R and then a string of lesser known and possibly less important genes such as CMP2 (Capillary Morphogenesis Protein 2).
Also worth noting is that the increased risk of AS of say x20 of one version of an SNP over the other version is only x20 specific to that particular SNP within that gene.
In the absence of at risk versions of HLA B27, ERAP1 and /or IL23R then the risk of AS associated with lower ranking genetic factors such as CMP2 or (presumably DHFRP2) is probably inconsequential.