Oxygen administration and the protection of health-care workers from infections.

disease, and a positive test result for antinuclear antibodies (ANAs) would not have been considered to have ssSSc. ANA positivity can occur in IPF patients, and thus we did not solely rely on this in our analysis. Rather, we highlighted the specificity of nucleolar staining for ANAs.3 In fact, in our previously described cohort of IPF subjects who were anti-Th/To-positive, we argued that, on retrospective analysis, those with ANAs revealed by nucleolar staining, and particularly those with Th/To antibodies, appeared to have had ssSSc-ILD.4 Dr. Singh states that antitopoisomerase antibodies have been reported in patients with IPF and suggests this could produce a nucleolar staining ANA. A closer review of the referenced article shows that 18 of 41 IPF patients (44%) had antibodies to DNA topoisomerase II.5 However, only 3 of the 18 patients had a positive ANA finding obtained by Hep2 cell substrate, and the pattern of immunofluorescence was not reported. Furthermore, to our knowledge, the presence of antitopoisomerase II antibodies in IPF patients has not been confirmed by another group, although it has been reported in Japanese patients with SScILD.6 Additionally, antitopoisomerase II antibodies should not be confused with antitopoisomerase I (anti-Scl-70) antibodies, which are highly specific for diffuse SSc and give a nucleolar pattern on ANA testing. Notably in our study, while all six patients had ANAs revealed by nucleolar staining, only one patient showed antitopoisomerase I (anti-Scl-70) antibodies. We believe that our case definition for ssSSc-ILD accurately differentiates those patients with ssSSc from those with IPF, and that this distinction is clinically useful.