C5b-9 plays an important role in the pathogenesis of immunoglobin A nephropathy (IgAN). We evaluated
C5b-9 as a prognostic marker for IgAN. We prospectively enrolled 33 patients with biopsy-proven IgAN. We analyzed the correlation between baseline urinary
C5b-9 levels, posttreatment changes in their levels, and clinical outcomes, including changes in
proteinuria, estimated glomerular filtration rate (eGFR), and treatment response. Baseline urinary
C5b-9 levels were positively correlated with
proteinuria (r = 0.548, p = 0.001) at the time of diagnosis. Changes in urinary
C5b-9 levels were positively correlated with changes in
proteinuria (r = 0.644, p < 0.001) and inversely correlated with changes in eGFR (r = -0.410, p = 0.018) at 6 months
after treatment. Changes in urinary
C5b-9 levels were positively correlated with time-averaged
proteinuria during the follow-up period (r = 0.461, p = 0.007) but were not correlated with the mean annual rate of eGFR decline (r = -0.282, p = 0.112). Baseline urinary
C5b-9 levels were not a significant independent factor that could predict the treatment response in logistic regression analyses (odds ratio 0.997; 95% confidence interval, 0.993 to 1.000; p = 0.078). Currently, urinary
C5b-9 is not a promising prognostic
biomarker for IgAN, and further studies are needed.