This suggests the potential role of PCSK9 as a marker to predict non-responsiveness to biological treatments in RA.271 Moreover, in a recent study involving 89 RA patients and 50 controls, higher blood PCSK9 levels were observed in RA patients, showing a positive correlation with Th17 cells, Th17/Treg ratio, CRP, and disease activity score (DAS), but not with Th1, Th2 cells, or Th1/Th2 ratio. Here, PCSK9 is linked to rheumatoid arthritis.