Yes, they've used different chips over the years.
If we have had the appropriate datas, we could have made more comparisons between your groups (ME from PR and control), to see
-prevalence of mutated alleles (how much polymorphisms for these 13 snp altogether in each group)
-prevalence of homozygotes for the mutated alleles (how much double for the 13 snp altogether polymorphisms for each group)
-prevalence of associations between some of these 13 mutated alleles (test different combinations of the 13 mutated alleles/snp and see if these combinations have different prevalences among the groups)
A pity we can't do more