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Complement factor C4 activation in patients with hereditary angioedema
Anne Aabom1, Anette Bygum1, Claus Koch2
1Department of Dermatology and Allergy Centre, Odense University Hospital, Odense, Denmark; OPEN, Odense Patient data Explorative Network, Odense University Hospital, Odense, Denmark.
Clinical Biochemistry
|April 17, 2017
Summary
Screening for hereditary angioedema with C1-inhibitor (C1-INH-HAE) using total antigenic C4 may miss patients. Measuring the C4c/C4 ratio is a more effective diagnostic measure for C1-INH-HAE.
Area of Science:
- Immunology
- Complement System
- Hereditary Angioedema
Background:
- Low complement factor C4 is a screening tool for C1-inhibitor deficiency hereditary angioedema (C1-INH-HAE).
- Some C1-INH-HAE patients have normal C4 levels, risking missed diagnosis.
- C4 activation products may improve diagnostic accuracy.
Purpose of the Study:
- To compare total antigenic C4 and non-functional C4c as measures of C4 activation in C1-INH-HAE.
- To determine the optimal diagnostic marker for C1-INH-HAE screening.
Main Methods:
- Developed monoclonal antibodies for total C4 and activated C4c.
- Assessed plasma from 19 Danish C1-INH-HAE patients using ELISAs.
- Measured total antigenic C4, functional C4, and non-functional C4c.
Main Results:
- Total antigenic C4 levels varied, with 2 patients showing normal levels.
- Functional C4 was low in all C1-INH-HAE patients.
- The C4c/C4 ratio identified non-functional C4 in about half of the measured C4 and captured all patients.
Conclusions:
- The C4c/C4 ratio is a superior diagnostic measure for C1-INH-HAE compared to total antigenic C4 alone.
- Relying solely on total antigenic C4 for screening poses a risk of overlooking C1-INH-HAE cases.