Seventy seven percent of RA patients with strong binding of the A2554 antibody were also RF positive (RF+, data not shown) and showed the highest levels of serum ANGPTL4 in the ELISA using the detection antibody from lot I. Based on these results we concluded that the capture antibody from DuoSet ELISA Development kit (DY3485, R&D Systems) bound RF and thus was the primary cause for the false positive detection of ANGPTL4. The gene discussed is ANGPTL4; the disease is rheumatoid arthritis.