Detection of anti-topoisomerase I antibodies by line immunoblot assay. Detection of anti-topoisomerase I (anti-topo I) antibodies by line immunoblot assay with respect to different levels of predicted diffusion capacity (DLCO) by a single breath (%), predicted forced vital capacity (FVC) (%) and modified Rodnan skin score (mRSS) values in 280 patients with systemic sclerosis (SSc) and diseases related to SSc. Numbers in bars, absolute counts. P values are results of the chi-square test. *For the chi-square test, because of the low case numbers in the last group, the last two mRSS groups were joined to hold the test assumptions (maximum 20% of cells have expected cell count < 5).