PRTN3 and juvenile idiopathic arthritis: Conversely, in the context of autoantibodies in JIA, it is worth noting that apart from Rheumatoid Factor (RF), which is used as a biomarker for diagnosis of JIA, information about other known autoantibodies, such as antibodies against citrullinated peptide/protein antigens (ACPA) and anti-nuclear antibodies (ANA), has not been utilised for classification of JIA subtypes.