In contrast, there was a significantly lower score in SpA versus RA for lining-layer thickness (P = 0.032), CD1a (P = 0.009), lymphoid aggregates (P = 0.029), anticitrulline staining (P < 0.001), and mAb 12A staining (P < 0.001). This evidence concerns the gene CD1A and rheumatoid arthritis.