Multiple logistic regression analysis of the remaining predictors, including anti-dsDNA, C4, ESR, and clinically detected synovitis, showed clinically detected synovitis had the most significant association with and the highest odds of US-detected inflammatory arthritis in the final model (aOR = 142.35, 95% confidence interval [CI] 6.55–3093.96; p = 0.002), as well as a borderline significant association with ESR levels (aOR = 1.04, 95% CI 1.00–1.08; p = 0.05). The gene discussed is C4A; the disease is synovitis.