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.