HLA-DRB1 and systemic lupus erythematosus: Although the positive association between the carrier frequency of DRB1*15:01 and SLE failed to reach significance in this set (Pc = 0.0705, odds ratio [OR] 1.76, 95% confidence interval [CI] 1.22–2.53, Table 1), a significant protective association was found for DRB1*13:02 and SLE (Pc = 0.0123, OR 0.42, 95% CI 0.26–0.68).