U1 and systemic sclerosis: When compared to other SSc-SA, anti-U11/U12 showed significantly stronger association with pulmonary fibrosis versus all other antibodies studied (anti-centromere, anti-PM/Scl, anti-RNA Pol III, anti-Th/To, anti-Scl-70, anti-U1 RNP, and anti-U3 RNP) with the exception of anti-Ku for which it is likely the number of cases was too low to reach statistical significance [36].