Can blood remaining in urine after six months help identify people with IgA nephropathy at greater risk of kidney decline?

Details

Proteinuria is a well-established surrogate marker in IgA nephropathy (IgAN), but the independent prognostic value of early hematuria remission remains unclear. The researchers hypothesized that treatment response at 6 months, particularly whether blood remained in the urine, would be associated with subsequent kidney outcomes.

They conducted a single-center retrospective cohort study of patients with biopsy-proven IgAN at Hiroshima University Hospital between April 2010 and March 2024. To minimize immortal time bias, they used a 6-month landmark analysis: only patients who were event-free at 6 months were included, and follow-up began at that point.

Patients were classified by urinary red blood cell (uRBC) count at 6 months: remission meant fewer than 5 red blood cells per high-power field (RBC/HPF), persistent moderate hematuria meant 5–29 RBC/HPF, and persistent severe hematuria meant at least 30 RBC/HPF. The primary outcome combined end-stage kidney disease or a decline of at least 30% in estimated glomerular filtration rate. The researchers used multivariable Cox models, Kaplan–Meier analyses, and restricted cubic spline models.

The analysis included 286 patients, with a median age of 43 years; 48.2% were male. During a median follow-up of 3.1 years, 38 patients (13.3%) reached the composite outcome. Compared with remission, persistent severe hematuria was associated with a higher risk of this outcome: hazard ratio 2.97, 95% confidence interval 1.33–6.67, P = 0.01. Restricted cubic spline analyses showed a graded association between higher uRBC counts and worse kidney outcomes.

The researchers concluded that persistent severe hematuria at 6 months was independently associated with worse kidney outcomes. Monitoring hematuria at 6 months may provide a clinically useful marker for risk stratification in patients with IgAN.