Mortality in patients with IgA nephropathy

Abstract

Background: Immunoglobulin A nephropathy (IgAN) is the most common glomerulonephritis globally. Few studies have investigated mortality in patients with IgAN compared with the age- and sex-adjusted general population.

Study design: Cohort study with record linkage between the Norwegian Kidney Biopsy Registry, Norwegian Cause of Death Registry, and Norwegian Renal Registry.

Setting & participants: 633 patients diagnosed with IgAN in 1988-2004.

Predictor: Estimated glomerular filtration rate (eGFR), age, and sex.

Outcomes: Deaths and causes of death before and after the onset of end-stage renal disease through 2008.

Results: Mean follow-up was 11.8 (range, 0-20.8) years. During the observation period, the observed number of deaths was 80 and the expected number was 42.1, resulting in a standardized mortality ratio (SMR) of 1.9 (95% CI, 1.5-2.4). Risk stratification based on initial eGFR showed that SMR was 1.0 (95% CI, 0.6-1.6) if eGFR was ≥60 mL/min/1.73 m(2), 1.9 (95% CI, 1.3-2.8) if eGFR was 30-60 mL/min/1.73 m(2), and 3.6 (95% CI, 2.6-5.0) in patients with eGFR <30 mL/min/1.73 m(2). Renal replacement therapy (RRT) was initiated in 146 patients and 35 of the 80 deaths occurred after the start of RRT. The age- and sex-adjusted SMR was not increased significantly in the pre-RRT period (1.3; 95% CI, 1.0-1.7), but was increased after initiation of RRT (4.9; 95% CI, 3.5-7.0). The most common cause of death was cardiovascular disease, accounting for 45% of all deaths.

Limitations: Treatment during follow-up is not known.

Conclusions: Mortality in patients with IgAN was twice the expected rate, but not significantly increased before RRT. The risk of end-stage renal disease was substantially higher than risk of death.

Keywords: Immunoglobulin A nephropathy; end-stage renal disease; mortality; prognosis; risk factor.