Serum C3 Range in Nephrotic Syndrome

Introduction to Nephrotic Syndrome and C3 Levels

In nephrotic syndrome, serum C3 levels are typically normal or elevated, unless there is concurrent complement-mediated glomerular disease, according to the American Society of Nephrology 1, 2

Low C3 levels in a patient with nephrotic syndrome should trigger investigation for specific complement-mediated diseases, such as C3 glomerulopathy, lupus nephritis, or infection-related glomerulonephritis, as recommended by the American Society of Nephrology 1, 3
Characterized by dominant C3 deposits with minimal or no immunoglobulin on kidney biopsy, C3 glomerulopathy is a condition that requires further investigation 3
Approximately 60-80% of patients over age 50 with C3 glomerulopathy have monoclonal gammopathy, according to the National Kidney Foundation 4

Persistently low C3 beyond 8-12 weeks after infection should prompt kidney biopsy to exclude C3 glomerulopathy, as suggested by the International Society of Nephrology 1, 5
In classical post-streptococcal glomerulonephritis, C3 normalizes within 8-12 weeks, according to the American Academy of Pediatrics 1

All complement factors, including C3, are typically depressed in active lupus nephritis, and screening with ANA, anti-dsDNA, and complement levels (C3, C4) is necessary, as recommended by the American College of Rheumatology 2, 6

When C3 is low in nephrotic syndrome, a diagnostic algorithm should be followed, including measuring C4 immediately, screening for infection, and performing an autoimmune workup, as suggested by the National Institute of Diabetes and Digestive and Kidney Diseases 1, 7
Kidney biopsy is mandatory when C3 remains low beyond 12 weeks or diagnosis is uncertain, according to the American Society of Nephrology 1, 5