Predictors of gross hematuria following SARS-CoV-2 mRNA vaccination in patients with IgA nephropathy.

Background There have been several reports of IgA nephropathy (IgAN) patients with gross hematuria and acute deterioration of urinary findings and kidney function following SARS-CoV-2 mRNA vaccination. Recent case series studies have indicated a possible link between the status of urinary findings at the time of vaccination and the subsequent appearance of gross hematuria. In this study, we aimed to determine whether the status of pre-vaccination urinary findings was associated with post-vaccination gross hematuria in patients already diagnosed with IgAN. Methods Outpatients with IgAN who had been followed up before vaccination were included. We analyzed the association between the remission of pre-vaccination microscopic hematuria (urine sediment <5 red blood cell/high power field) or proteinuria (<0.3 g/gCr) and post-vaccination gross hematuria. Results A total of 417 Japanese patients with IgAN (median age, 51 years; 56% female; estimated glomerular filtration rate (eGFR), 58 mL/min/1.73 m2) were included. The frequency of gross hematuria following vaccination was higher in 20/123 patients (16.3%) with microscopic hematuria than in 5/294 patients (1.7%) without microscopic hematuria prior to vaccination (P <0.001). There was no association between pre-vaccination proteinuria and post-vaccination gross hematuria. After adjusting for potential confounders, such as sex (female), age (<50 years), eGFR (≥60 mL/min/1.73 m2), and histories of tonsillectomy and corticosteroid therapy, pre-vaccination microscopic hematuria was still associated with post-vaccination gross hematuria (OR 8.98, P <0.001). As the severity of pre-vaccination microscopic hematuria increased, the incidence of post-vaccination gross hematuria increased (P <0.001). Conclusions Pre-vaccination microscopic hematuria in patients with IgAN is a major predictor of post-vaccination gross hematuria, regardless of potential confounders including previous treatments for IgAN.