Complement Total (CH50) Test

The Complement Total (CH50) Test is a functional assay that measures the overall activity of the classical complement pathway. It is used to investigate suspected complement deficiencies, monitor autoimmune conditions such as systemic lupus erythematosus (SLE), and assess disease activity in immune complex disorders. The test is suitable for patients with recurrent infections, unexplained angioedema, or a family history of complement deficiency, as well as for clinicians monitoring treatment response in complement-mediated diseases.

The CH50 test works by adding a standardised amount of antibody-sensitised sheep red blood cells to the patient's serum. If the complement system is functioning normally, it will lyse the red blood cells, and the degree of haemolysis is measured spectrophotometrically. The result is expressed as the dilution of serum required to lyse 50% of the red blood cells, hence the name CH50. This provides a sensitive, global assessment of the classical pathway, including the function of C1 through C9.

Biomarkers
- Complement Total (CH50)

Why it matters
The complement system is a vital part of innate immunity, and its dysfunction can lead to severe infections, autoimmune tissue damage, or hereditary angioedema. A low CH50 result may indicate a deficiency in one or more complement components, consumption due to active immune complex disease, or a genetic defect. Early detection guides further component-specific testing, informs treatment decisions, and helps prevent complications such as renal failure or recurrent meningococcal infections. For patients with known autoimmune conditions, serial CH50 measurements can track disease flares and response to therapy.

• Complement Total (CH50)

No special preparation required.

For blood tests, we recommend drinking plenty of water beforehand to ensure smooth sample collection. If you are taking any regular medication, continue to do so unless advised otherwise by your doctor.