Soluble Tyro-3 and Axl may reflect the current activity and renal involvement in patients with microscopic polyangiitis and granulomatosis with polyangiitis.

Objectives: This study investigated whether soluble Tyro-3 (sTyro-3), sAxl, and sMer could reflect the current activity in patients with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA).

Methods: This study retrospectively reviewed the medical records of 76 patients with MPA and GPA, and measure the serum concentrations of sTyro-3, sAxl, and sMer using the stored serum at AAV diagnosis. Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV)-specific indices included Birmingham vasculitis activity index (BVAS), five-factor score, the short-form 36-item health survey, and vasculitis damage index. High AAV activity was defined as the highest tertile of BVAS.

Results: The median age of the 47 MPA and 29 GPA patients was 66.0 years and 43.4% were men. The serum concentrations of sTyro-3 and sAxl were significantly correlated with BVAS and the total score of renal manifestation. The serum concentrations of sTyro-3 and sAxl were independently correlated with BVAS (β=0.343 and β=0.310, respectively). In addition, the serum concentrations of sTyro-3 and sAxl were independently associated with the renal involvement of MPA and GPA (OR 1.003 and OR 1.055, respectively).

Conclusions: This study demonstrated the potential of the serum concentrations of sTyro-3 and sAxl to reflect the current activity and renal involvement in patients with MPA and GPA.