MO226: Is Remission of Hematuria Associated with Kidney Outcome in Biopsy-Proven Primary IGA Nephropathy?

Abstract

Abstract BACKGROUND AND AIMS Microscopic hematuria, associated with variable proteinuria, is the most common clinical feature of IgA nephropathy (IgAN). However, its role in the disease progression is still controversial. This study aims to assess whether remission of hematuria is associated with kidney outcome in adults with primary IgAN. METHOD This retrospective, longitudinal study enrolled 62 adults, out of 214 with biopsy-proven IgAN between 1 January 2008 and 31 December 2017 {age 41 [95% confidence interval (CI) 37–46] years, 73% males, eGFR 41.3 (95% CI 33.1–51) mL/min and proteinuria 1.1 (95% CI 0.9–1.6) g/g} who had at least three assessment visits 3 months apart until 31 May 2018. The median follow-up period was 68 (95% CI 58.6–77.3) months. Demographic (age, gender), comorbidities, clinical and laboratory data (proteinuria, hematuria and blood pressure) at the time of kidney biopsy and during the follow-up period were retrieved from medical records. Information about therapy was also recorded. The study endpoint was kidney death defined as doubling of serum creatinine or renal replacement therapy (RRT) initiation. Kidney survival was evaluated by Kaplan–Meier method and variables related to kidney outcome by multivariate Cox proportional hazard modeling. Remission of hematuria was defined as ≤ 5 red blood cells/high power field in at least two samples taken no less than 3 months apart. Subjects were grouped as remission of hematuria (n = 24) and persistent hematuria (n = 38). RESULTS There were no differences between the two groups regarding demographic characteristics, comorbidities, kidney function, proteinuria, hematuria or inflammation markers at time of kidney biopsy. During the follow-up period, remission of proteinuria (defined as a > 50% decrease in urinary protein-to-creatinine ratio from baseline) was found in more than half of the group with remission of hematuria but in less than a quarter of group with persistent hematuria (57.1% versus 24.2%; P = .02). However, systolic blood pressure was well controlled (<130 mmHg) in similar proportions (63.6 versus 57.9%, P = .7) and a comparable reduction in mean arterial blood pressure from the baseline was observed [ΔMAP −7.8 (95% confidence interval (CI) −14.1 to −0.45) versus −2.8 (95% CI −9.7–4.9) mmHg; P = .2] in both groups. A high proportion of patients were treated with renin–angiotensin inhibitors (71 versus 61%; P = .5) and almost a third received immunosuppressive therapy (38 versus 34%; P = .8), similarly in the two groups. During the follow-up, a lower proportion of patients with remission of hematuria reached the composite kidney endpoint (16.7 versus 42.1%, P = .03). In the univariate time-dependent analysis, the kidney survival was numerically better in patients with remission of hematuria [(71.4 (95% CI 64.5–78.2) versus 66.02 (95% CI 54.7–77.2) months; log rank P = .06; Fig. 1A]. However, in the multivariate time-dependent analysis, only the absence of proteinuria remission [OR 0.06 (95%CI 0.008–0.46), P = .007] and a lower baseline eGFR [OR 0.96 (95% CI 0.93–0.98), P = .007] were associated with a poor kidney outcome (chi-squared = 18.5, P < .001) (Fig. 1B). CONCLUSION In this cohort of young adults with biopsy-proven primary IgA nephropathy and moderate decline in kidney function, the remission of hematuria for at least 3 months was not associated with kidney outcome.