Population and Proteinuria Comparison Between UK and Chinese IgAN Patients

Proteinuria is a common symptom of IgA nephropathy (IgAN) and serves as a surrogate endpoint for predicting long-term outcomes of the disease. KDIGO guidelines call for proteinuria <1 g/day as a therapeutic target, yet a recent study in China suggested a lower threshold of <0.3 g/day (approximately 26 mg/mmol).

In a poster presentation at ASN Kidney Week 2024, a group of researchers led by Jonathan Barratt, PhD, shared results from an evaluation and comparison of population characteristics and proteinuria findings of Chinese and UK cohorts with IgAN. The poster was titled Concordance of Proteinuria Thresholds between Chinese and UK Cohorts with IgA Nephropathy.

The analysis included 3,493 patients with biopsy-proven IgAN from the UK RaDaR registry, one of the largest and most comprehensive population-based datasets for patients with the disease. More patients in the UK cohort were male (70.5%) compared to the Chinese patients (51.4%). The UK patients also tended to be older (42.8±14.4 years) than the Chinese patients (36.5±12.0 years). A larger percentage of UK patients (69.2%) were at stage 3 or higher CKD than their Chinese counterparts (30.8%). UK patients also had lower eGFR (47.8±31.0 vs 78.43±30.45 mL/min/1.73 m²).

During follow-up, 2,040 (58%) of the UK patients advanced to kidney failure and their median survival was eight (7.5-8.7) years. Median survival directly correlated with proteinuria and was notably lower among patients with proteinuria ≥100 mg/mmol (HR, 3.072; 95% CI, 2.32-4.06). Median survival for patients with proteinuria <50, 50-99, 100-199, 200-299, and >300 mg/mmol was 10.4 (7.3-NE), 9.7 (7.6-NE), 5.8 (4.3-7.7), 3.3 (2.1-4.8), and 1.4 (0.9-1.9) years, respectively.

Although some differences were observed across populations, IgAN patients with certain characteristics consistently had a worse prognosis. Even when levels are below the current KDIGO threshold, proteinuria indicates a risk of kidney failure. Due to this finding, it may be worth considering a lower threshold.

Source: Barratt J, Pitcher D, Hirst C, Gale DP. Concordance of proteinuria thresholds between Chinese and UK cohorts with IgA nephropathy. FR-PO858. Abstract of a poster presented at the American Society of Nephrology Kidney Week 2024; October 25, 2024; San Diego, California. Funding for the study was provided by Novartis Pharma AG.