The Complement AH50 blood test, also known as the Alternative Pathway Hemolytic Assay, measures the functional activity of the alternative pathway of the complement system. The complement system is a crucial part of the immune response, consisting of proteins that enhance the ability to fight infections, clear damaged cells, and promote inflammation. Unlike the classical pathway, the alternative pathway can be activated without the presence of antibodies, making it an important first line of defense against pathogens.
In the AH50 test, a blood sample is taken from the patient and mixed with rabbit red blood cells. These cells are used because they readily activate the alternative complement pathway. The test measures the ability of the patient's complement proteins to lyse, or break down, these red blood cells. The degree of hemolysis is quantified and reported as an AH50 value. A normal AH50 value indicates that the alternative pathway components are present and functioning correctly.
Abnormal AH50 results can point to various medical conditions. A low AH50 level suggests a deficiency or dysfunction in one or more components of the alternative pathway, which could be due to genetic factors, autoimmune diseases, or certain infections. Specific deficiencies, such as in factors B, D, or properdin, can lead to low AH50 levels and result in increased susceptibility to infections and other immune-related issues.
The AH50 test is particularly useful for diagnosing and monitoring diseases that involve complement system dysfunction. It is often used in conjunction with the CH50 test, which assesses the classical pathway, to provide a comprehensive evaluation of complement activity. This combined approach helps healthcare providers identify specific complement deficiencies and tailor treatment plans to address the underlying causes of immune system dysregulation.