17% of 1st degree relatives AS pts had MRI- defined sacroiliitis, however not all of them were diagnosed w/ SpA due to absence of back pain. 25% w/ 1st degree AS relative met the classification criteria for SpA #ACR23 Abs #1403 https://t.co/W1T9ZqD4o1 @rheumnow https://t.co/DnaNSLiqfU