Serum soluble programmed cell death protein 1 could predict the current activity and severity of antineutrophil cytoplasmic antibody-associated vasculitis: a monocentric prospective study

OBJECTIVES: We investigated whether serum soluble programmed cell death protein 1 (sPD-1) could predict the current activity and severity of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) based on Birmingham vasculitis activity score (BVAS) in patients with AAV. METHODS: Fifty-nine patients from a monocentric prospective cohort of AAV were included. On the same visit-day, blood samples were collected and isolated sera were stored, BVAS and other AAV-related parameters were assessed, and laboratory tests were performed. We defined the lower limit of the highest tertile of BVAS as the cut-off for severe AAV (BVAS ≥12). Serum sPD-1 was measured from stored serum samples. RESULTS: The mean age was 59.7 years (38 women). The mean BVAS was 8.9 and 18 patients had severe BVAS. Patients with severe AAV exhibited the higher mean serum sPD-1 than those without (380.7 pg/mL vs. 180.3 pg/mL). Serum sPD-1 (r=0.367), white blood cell count (r=0.288), haemoglobin (r=-0.590), serum albumin (r=-0.670) erythrocyte sedimentation rate (ESR) (r=0.339) and C-reactive protein (CRP) (r=0.450) were significantly correlated with BVAS. Moreover, serum sPD-1 was meaningfully correlated with haemoglobin and serum albumin, but not ESR or CRP. In the multivariable linear regression analysis, only serum sPD-1 was significantly associated with BVAS (standardised β 0.274, p=0.024). We calculated the optimal cut-off of serum sPD-1 for severe AAV as 70.1 pg/mL. Severe AAV were more frequently identified in patients with serum sPD-1 ≥70.1 pg/mL than those without (RR 13.867). CONCLUSIONS: Serum sPD-1 could predict the current activity and severity of AAV.