PAD-4 Autoantibodies Identified as a Novel Severity Factor in RA September 30, 2008 By Arthritis Center …only 1 of 126 patients (0.8%) with other rheumatic diseases (scleroderma, myositis, lupus, and primary Sjogren’s)—yielding a sensitivity of 42% and specificity of 99% for RA. Clinical characteristics of PAD4…