Association of Lupus Nephritis Histopathologic Classification With Venous Thromboembolism—Modification by Age at Biopsy

INTRODUCTION: Lupus nephritis (LN) is an independent risk factor for venous thromboembolism (VTE). The risk of VTE has not been analyzed by International Society of Nephrology/Renal Pathology Society or World Health Organization LN class. Study goals were to measure VTE incidence in an LN patient cohort, to evaluate associations between VTE and LN class, and to investigate factors modifying associations between VTE and LN class. METHODS: A retrospective analysis was performed using Glomerular Disease Collaborative Network data. Image-confirmed VTE was compared between patients with any LN class V lesion and patients with only LN class III or IV. Logistic regression was used to calculate odds ratios and 95% confidence intervals. Effect modification was assessed between main effect and covariates. RESULTS: Our cohort consisted of 534 LN patients, 310 (58%) with class III/IV and 224 (42%) with class V with or without class III/IV, including 106 with class V alone. The VTE incidence was 62 of 534 (11.6%). The odds of VTE were not significantly different between patients with class III/IV and class V in adjusted analyses (odds ratio [OR] = 0.82, 95% confidence interval [CI] = 0.45−1.48). An age interaction was observed (P = 0.009), with increased odds of VTE with class III/IV diagnosed at a younger age (2.75, 0.90−8.41 estimated at age 16 years) and decreased odds with class III/IV diagnosed at an older age (0.23, 0.07−0.72 estimated at age 46 years), compared to class V. CONCLUSIONS: The VTE incidence was similar among patients with LN classes III/IV and V, suggesting that VTE risk is not limited to class V−related nephrotic syndrome and that age may modulate LN class-specific VTE risk.