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

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.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.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).Serum sPD-1 could predict the current activity and severity of AAV.