Complement Factor H and Factor I
| Category | Immunology |
|---|---|
| Test background |
Factor H and I are regulators of the complement cascade. Factor H is a co-factor for factor I mediated cleavage of alternative pathway C3b into iC3b and it competes with factor B to prevent formation of the alternative pathway C3 convertase. Dysregulated alternative pathway regulation is a cause of dense deposit disease (DDD) and can be caused by C3 nephritic factors, anti-Factor H antibodies and genetic loss of function mutations of Factor H. Factor H deficiency may also cause atypical haemolytic uremic syndrome (aHUS). |
| Clinical Indications |
HUS |
| Reference range | Factor H = >0.43 g/L Normal values do not exclude genetic mutations in Factor H & I |
| Sample & container required | Serum (RST rust top) |
| Sample volume | 5-10 mL blood (1 mL serum) |
| Turnaround time | 28 days |
| Notes | Not currently performed in house. This test is performed by radial immunodiffusion at Royal Victoria Hospital, Newcastle |