IL1A and systemic sclerosis: When stratifying patients into high and low serum IL‐1α subsets, using the median IL‐1α concentration (17.1 pg mL−1) as a cut‐off, we observed a higher proportion of SSc patients with digital ulcers in the high serum IL‐1α subset than in the low serum IL‐1α subset (Supplementary table 7).