Through the development of a microfluidic chip-based method, Wang and colleagues identified two high-potential IgG sulfated N-glycan biomarkers for the classification of both rheumatoid factor (RF)-positive and -negative RA patients, as well as anti-citrullinated protein antibody (ACPA)-positive and -negative RA patients[148]. The gene discussed is PRTN3; the disease is rheumatoid arthritis.