Modified Body Mass Index at Diagnosis is a Useful Predictor of Mortality in Patients With Antineutrophil Cytoplasmic Antibody-associated Vasculitis

Objective: We investigated whether modified body mass index (mBMI) at diagnosis could predict all-cause mortality during follow-up in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Methods: The medical records of 203 AAV patients with BMI ≥18.5 kg/m² were reviewed. mBMI was calculated using an equation: mBMI=BMI (kg/m²)×serum albumin (g/L). All-cause mortality was considered as a poor outcome, and the follow-up duration based on all-cause mortality was defined as the period from AAV diagnosis to death for deceased patients, and the period from AAV diagnosis to the last visit for surviving patients. Results: The median age was 59.0 years (35.5% were male). The median BMI and mBMI were 22.8 kg/m² and 813.2 kg·g/m²·L. Twenty-five patients (12.3%) died. mBMI was well correlated with age, BVAS, FFS, erythrocyte sedimentation rate and C-reactive protein at diagnosis. Deceased patients exhibited significantly lower mBMI at diagnosis compared to surviving patients. AAV patients mBMI ≤570.1 kg·g/m²·L showed a significantly higher frequency of all-cause mortality (38.5% vs. 8.5%), and furthermore, exhibited a significantly higher risk for all-cause mortality than those with mBMI >570.1 kg·g/m²·L (RR 6.750). mBMI ≤570.1 kg·g/m²·L showed a significantly lower cumulative patients’ survival rate than those with mBMI >570.1 kg·g/m²·L. In the multivariable Cox hazards model analysis, either serum albumin or mBMI was significantly associated with all-cause mortality in AAV patients. Conclusion: In conclusion, mBMI ≤570.1 kg·g/m²·L at diagnosis may be a useful predictor of all-cause mortality during followup additionally to serum albumin in AAV patients.