Further, ACA-positive and ACA-negative patients did not differ in their mean plasma/serum IFN-α (13.3 vs. 13.1 pg ml−1, P = 0.28, N = 25, discovery SSc cohort; 398 vs. 403 pg ml−1, P =0.1, N = 49, replication SSc cohort). The gene discussed is IFNA1; the disease is systemic sclerosis.