From the Guidelines
Complement Levels in Post-Streptococcal Glomerulonephritis
Complement levels, specifically C3, are typically decreased during the acute phase of post-streptococcal glomerulonephritis (PSGN) 1.
- The degree of C3 depression can vary, but it is often more pronounced in patients with severe disease.
- Serial measurements of C3 levels can be useful in monitoring disease activity and response to treatment.
- Levels usually return to normal within 8-12 weeks 1.
- Persistently low C3 in serum beyond week 12 may be an indication for kidney biopsy to exclude complement C3 glomerulonephritis (C3GN) 1.
- No specific medication, such as corticosteroids or immunosuppressants, is typically required for complement level management in PSGN.
- C4 levels may also be assessed, but the primary focus is on C3 levels in the context of PSGN 1.
From the Research
Complement Levels in Post-Streptococcal Glomerulonephritis
- Complement levels are decreased in patients with post-streptococcal glomerulonephritis (PSGN), with low serum C3, properdin, and C5 levels indicating aggressive complement activation 2, 3, 4.
- The classical complement pathway is frequently activated in patients with PSGN, with elevated C4d/C4 ratios indicating C4 activation 5.
- C3 and C5 levels are decreased in PSGN, with C3 levels being decreased in more than 90% of cases 4.
- C4 levels are typically normal or only slightly decreased in PSGN, with the early return to normal of fourth component concentrations being a favourable prognostic sign 2, 5.
- Other complement components, such as C6 and C8, may also be decreased in some patients with PSGN, particularly those with low C3 levels 5.
Patterns of Complement Activation
- Complement activation in PSGN is thought to occur through the alternative pathway, with C3 splitting activity present before the clinical onset of nephritis 3.
- The activation of the classical pathway also plays a role in PSGN, with C4 activation occurring in some patients 5.
- The pattern of complement activation in PSGN is distinct from that seen in other types of glomerulonephritis, such as systemic lupus erythematosus 2.
Clinical Implications
- Decreased complement levels, particularly C3, are a hallmark of PSGN and can be used to diagnose and monitor the disease 4, 6.
- Measuring C3 and C4 levels may also be helpful in evaluating other causes of acute nephritis 4.
- The management of PSGN is mainly supportive, with fluid restriction, anti-hypertensives, diuretics, and renal replacement therapy as needed 6.