Novel mortality‐predicting index at diagnosis can effectively predict all‐cause mortality in patients with antineutrophil cytoplasmic antibody‐associated vasculitis

BACKGROUND: This study investigated whether the inflammation prognostic index (IPI) and the mortality predicting index (MPI) at diagnosis could predict all‐cause mortality in patients with antineutrophil cytoplasmic antibody (ANCA)‐associated vasculitis (AAV). METHODS: We included 223 AAV patients and reviewed their medical records. Clinical and laboratory data and AAV‐specific indices at diagnosis were assessed. The IPI was calculated as neutrophil‐to‐lymphocyte ratio (NLR) × C‐reactive protein to albumin ratio (CAR). Here, we newly developed an MPI (NLR × CAR × monocyte counts). RESULTS: The mean age of 223 patients (122 MPA, 57 GPA and 44 EGPA patients) was 59 years. The rate of mortality was 11.2%. Using the receiver operator characteristic curve for all‐cause mortality, the cut‐offs were calculated as NLR: 3.22, CAR: 3.25, IPI: 18.53 and MPI: 8367.82. In the univariable Cox hazard analysis, age, gender, smoking history, BVAS, FFS and over the cut‐off of each index showed statistical significance. As the indices share at least two mutual variables, the multivariable analysis was conducted four times based on each index. An IPI ≥18.53 (HR 3.162) and MPI ≥8367.82 (HR 3.356) were significantly associated with all‐cause mortality. CONCLUSIONS: This study developed a novel indicator, MPI, that uses the existing NLR and CAR indices and proved that it could predict all‐cause mortality in AAV patients.