Editing Complement system (section)

=== Diagnostic tools ===
Diagnostic tools to measure complement activity include the [[total complement activity]] test.<ref>{{Cite web |title=Complement Deficiencies Workup: Laboratory Studies, Imaging Studies, Other Tests |url=https://emedicine.medscape.com/article/135478-workup |access-date=2018-04-26 |website=emedicine.medscape.com |language=en}}</ref>

The presence or absence of complement fixation upon a challenge can indicate whether particular antigens or antibodies are present in the blood. This is the principle of the [[complement fixation test]].{{cn|date=July 2024}}