While this obviously reduces the power of the study, the same is true for the number of target genes: adding more genes to the list, would have increased the number of tagging SNPs resulting in even bigger type I error bias due to multiple testing.[29] Therefore, no other gene of the purinergic pathway was chosen in addition to CD73, although ENPP1,[30] for-instance, is also well known to be associated with vascular calcification. This evidence concerns the gene ENPP1 and calcification.