Complement assays

Unlocking the potential of complement testing in immune disorders


What are complement assays?

The complement system is a crucial component of our innate immune system that supports the body's defense against injuries and infections. Its functions include activation of the inflammatory response, phagocytosis-mediated destruction of bacteria and viruses, pathogen agglutination, and cell lysis of susceptible organisms.

There are three distinct pathways through which the complement cascade can be activated, each triggered by different mechanisms. These pathways involve more than 50 different proteins.

Complement testing is recommended for the assessment of specific complement disorders.1

Understand more about immunological disorders
Primary immunodeficiency, secondary immunodeficiency and inborn error of immunity

Range of assays

Comprehensive assay portfolio 

  • Comprehensive and optimized assays for quantification and functional assessment of complement. These assays are included in clinical guidelines2
  • The functional CH50 assay is used to measure classical complement pathway activity and can be used to investigate complement deficiencies
  • The complement component (C4, C1 Inactivator) assays aid in the determination of immune deficiencies, such as hereditary angioedema (HAE) and acquired angioedema (AAE) 

Primary immunodeficiency screening 


E. de Vriesin collaboration with European Society for Immunodeficiencies (ESID) members developed a protocol to screen for primary immunodeficiency

Precision diagnostics 

Complement assays are optimized for use with Optilite® Analyser and categorized into functional assays and protein concentration assays.

Human complement functional assay – CH50  Human complement protein assay - C1 inactivator
This functional assay aids in the characterization of classical complement pathway activity, and therefore aids in the investigation for complement deficiencies. This assay may be used where there is a clinical suspicion of immunological disorders. This assay quantifies the levels of C1i and can therefore aid in the characterization of complement deficiencies. The assays are also cleared as an aid in the diagnosis of hereditary angioedema. 
Human complement protein assay - C3 Human complement protein assay - C4
This assay quantifies the levels of C3 and can therefore aid in the characterization of complement deficiencies. This assay could be used if there is a suspicion of immunodeficiencies or as further testing dependent on initial tests. This assay quantifies the levels of C4 and can therefore aid in the characterization of complement deficiencies. Inherited or acquired deficiencies in C1 inhibitor cause decreased serum levels of C4, which are associated with angioedemas.


Optilite® CH50 enhanced productivity 

  • Automated – Quantifiable, quality results to avoid subjective interpretation
  • Optimized - Consistent, reliable results instills clinical trust
  • Fast – Turn around time of ~15 minutes to deliver timely clinical care
  • On board reagent stability of 30 days helps save on reagent cost
  • Shows good correlation when compared with conventional methods
  • Defined reference limits and measuring ranges for serum and plasma for user convenience 


*The ranges provided in the image have been obtained from a limited number of samples and are intended for guidance purposes only. Expected values may vary with age, sex, sample type, diet and geographical location. Each laboratory should verify the transferability of the expected values to its own population and, if necessary, determine its own reference interval. 
Optilite is a registered trademark of The Binding Site Group Ltd (Birmingham, UK) in certain countries.


Liposome-based CH50 method 

  • Automated method for quick functional assessment of the classical complement pathway
  • Uses antigen-coated liposomes encapsulating glucose-6-phosphate dehydrogenase (G6PDH) enzyme which are further sensitized with antibodies
  • When reagents are mixed with the clinical sample, complement in the sample is activated by Ag/Ab complexes on the liposome surface, resulting in liposome lysis and the release of G6PDH
  • G6PDH then reduces NAD to NADH, causing a measurable change in absorbance proportional to the complement activity in the sample
Immune Disorders
Immune Disorders
Immune Disorders

Learn more about the immune disorders that our complement assays aim to help diagnose and monitor.
Optilite® Analyser
Optilite® Analyser

Transform your diagnostics with Optilite® - a fully automated, robust benchtop analyser for special protein testing.
Contact Us?
Questions about our products or services? Our team is ready to hear them.

Complete this form and we will get back to you

By submitting this form you agree to Thermo Fisher Scientific Inc. Terms of Use and Privacy Notice, including transfer of your personal data to countries outside your country of residence.

1. Lung, Thomas et al. “The utility of complement assays in clinical immunology: A comprehensive review.” Journal of autoimmunity vol. 95 (2018): 191-200.
2. Antonis Fanouriakis et al. Ann Rheum Dis 2021;80:14-25