이전에 발표된 여러 연구는 SE와 항-CCP 양성 RA 뿐만 아니라 항-CCP 항체 음성과의 연관성을 보고했다.
Several previously published studies have reported the association of the SE and smoking with anti-cyclic citrullinated peptide (CCP) negative as well as anti-CCP positive RA.