HMGCR and ankylosing spondylitis: For the primary outcome, assuming that the per mmol/L decrement in LDL cholesterol by the HMGCR score resulted in a twofold decrease in the odds of ankylosing spondylitis, the current sample size of the primary cohort would have a 97.4% power to obtain an estimate with a two-sided significance level of 0.05 (Supplementary Figure 2).