Pretreatment neutrophil-to-lymphocyte ratio is associated with clinical phenotypes and infection-related mortality in microscopic polyangiitis: the multicentre REVEAL cohort study

Background Microscopic polyangiitis (MPA) remains associated with substantial early mortality despite advances in immunosuppressive therapy, highlighting the need for simple biomarkers that facilitate LR) has been associated with disease activity and prognosis in antineutrophil cytoplasmic antibody-associated vasculitis (AAV), its phenotype-specific significance in newly diagnosed MPA remains unclear. We investigated whether pretreatment NLR is associated with clinical phenotype, disease course, and long-term outcomes in MPA. Methods Among 418 patients with MPA enrolled in the multicentre REVEAL cohort between 2005 and 2025, 340 newly diagnosed treatment-naïve patients fulfilling the 2022 ACR/EULAR classification criteria were included. Patients were stratified into tertiles according to pretreatment NLR. Baseline characteristics, temporal outcomes, and survival were compared. Infection-related mortality was further evaluated after stabilised inverse probability weighting (IPW). Results Higher pretreatment NLR was associated with greater disease severity, including higher Birmingham Vasculitis Activity Score ( P < 0.001) and Five-Factor Score ( P = 0.03), more frequent diffuse alveolar haemorrhage ( P = 0.015), poorer renal function ( P = 0.003), and more intensive remission-induction therapy, including methylprednisolone pulse therapy and rituximab. In contrast, interstitial lung disease was more common in patients with lower NLR ( P = 0.001). Despite these baseline differences, disease activity, glucocorticoid tapering, and cumulative organ damage became comparable after treatment initiation. Pretreatment NLR was not associated with relapse-free survival ( P = 0.44) but was associated with poorer overall survival ( P = 0.012) and higher infection-related mortality ( P = 0.002). After adjustment using IPW, the association with overall survival was no longer statistically significant, whereas the increased risk of infection-related mortality remained significant (HR 3.47, 95% CI 1.32–9.09, P = 0.034). Conclusion Pretreatment NLR reflected distinct inflammatory phenotypes and was independently associated with infection-related mortality in patients with newly diagnosed MPA. As an inexpensive and widely available marker, pretreatment NLR may have potential as a prognostic biomarker, although further validation is required to establish its clinical utility.