A 35-year-old woman with a 5-year history of recurrent gross hematuria (3–4 episodes per year, each lasting 2–3 days) is found to have persistent microscopic hematuria, mild proteinuria (0.8 g/day), and normal serum creatinine. Serum complement levels are normal. Kidney biopsy shows IgA-dominant deposits on immunofluorescence. Which single feature best distinguishes her IgA nephropathy from rapidly progressive glomerulonephritis (RPGN)?