Ethnic Differences in Incidence and Outcomes of Childhood Nephrotic Syndrome

Abstract

Background and objectives: Ethnic differences in outcomes among children with nephrotic syndrome are unknown.

Design, setting, participants, & measurements: We conducted a longitudinal study at a single regional pediatric center comparing ethnic differences in incidence from 2001 to 2011 census data and longitudinal outcomes, including relapse rates, time to first relapse, frequently relapsing disease, and use of cyclophosphamide. Among 711 children, 24% were European, 33% were South Asian, 10% were East/Southeast Asian, and 33% were of other origins.

Results: Over 10 years, the overall incidence increased from 1.99/100,000 to 4.71/100,000 among children ages 1-18 years old. In 2011, South Asians had a higher incidence rate ratio of 6.61 (95% confidence interval, 3.16 to 15.1) compared with Europeans. East/Southeast Asians had a similar incidence rate ratio (0.76; 95% confidence interval, 0.13 to 2.94) to Europeans. We determined outcomes in 455 children from the three largest ethnic groups with steroid-sensitive disease over a median of 4 years. South Asian and East/Southeast Asian children had significantly lower odds of frequently relapsing disease at 12 months (South Asian: adjusted odds ratio; 0.55; 95% confidence interval, 0.39 to 0.77; East/Southeast Asian: adjusted odds ratio; 0.42; 95% confidence interval, 0.34 to 0.51), fewer subsequent relapses (South Asian: adjusted odds ratio; 0.64; 95% confidence interval, 0.50 to 0.81; East/Southeast Asian: adjusted odds ratio; 0.47; 95% confidence interval, 0.24 to 0.91), lower risk of a first relapse (South Asian: adjusted hazard ratio, 0.74; 95% confidence interval, 0.67 to 0.83; East/Southeast Asian: adjusted hazard ratio, 0.65; 95% CI, 0.63 to 0.68), and lower use of cyclophosphamide (South Asian: adjusted hazard ratio, 0.82; 95% confidence interval, 0.53 to 1.28; East/Southeast Asian: adjusted hazard ratio, 0.54; 95% confidence interval, 0.41 to 0.71) compared with European children.

Conclusions: Despite the higher incidence among South Asians, South and East/Southeast Asian children have significantly less complicated clinical outcomes compared with Europeans.

Keywords: Asian Continental Ancestry Group; Ethnic Groups; European Continental Ancestry Group; Humans; Incidence; Longitudinal Studies; Recurrence; children; cyclophosphamide; ethnicity; nephrotic syndrome; steroids.

Copyright © 2016 by the American Society of Nephrology.

Figures

Figure 1.

Proportion of frequently relapsing nephrotic syndrome and absolute number of relapses by ethnicity among 455 children with nephrotic syndrome (1993–2014). (A) Data by ethnicity shows frequently relapsing nephrotic syndrome at 6, 12, and 18 months from diagnosis. (B) Absolute total number of relapses by ethnicity. (C) Absolute number of relapses after treatment with cyclophosphamide. *P value ≤0.05; ***P value ≤0.001.

Figure 2.

Kaplan–Meier cumulative probability curves for time to first relapse and time to cyclophosphamide by ethnicity. (A) Developing first relapse from diagnosis of nephrotic syndrome in days. (B) Use of cyclophosphamide from diagnosis of nephrotic syndrome in years.