Biological treatment in ankylosing spondylitis in the Nordic countries during 2010-2016: a collaboration between five biological registries. - On behalf of: the DANBIO Registry, Copenhagen, Denmark; the SRQ/ARTIS Registry, Stockholm, Sweden; the ROB-FIN Registry, Helsinki, Finland; the NOR-DMARD Registry, Oslo, Norway; the ICEBIO Registry, Reykjavik, Iceland; Glintborg, B; Hetland, ML; Kristensen, LE; Jørgensen, TS; Eklund, K; Grondal, G; Geirsson, AJ; Jonsson, H; Joensuu, J; Törmänen, MRK; Skydsgaard, H; et al. (Scandinavian Journal of Rheumatology, 2018)