Complement C1 esterase inhibitor – functional
| Category | Immunology |
|---|---|
| Test background |
Functional C1 inhibitor levels must be requested alongside antigenic C1 inhibitor (see C1 esterase inhibitor – antigenic) and C3 and C4. This test aids diagnosis of type II HAE, affecting 15 % of sufferers. A low C4, plus a normal or raised C1 inhibitor antigenic level, is associated with low/absent C1 inhibitor functional activity. In type I HAE, patients have a low C1 inhibitor antigenic level and low functional activity. |
| Clinical Indications |
Recurrent angioedema, laryngeal oedema, or abdominal pain in the absence of urticaria Family history |
| Reference range | 0.7-1.3 g/L |
| Sample & container required | Plain tube (Rust; Serum) |
| Sample volume | 1 mL serum |
| Transport storage | For external users, separate and freeze immediately. Transport frozen. For internal users, transport to I&I ASAP |
| Turnaround time | 21 days |