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Immunology Laboratory

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Complement Activity - Classical and Alternative Pathways

Also known as: CH50; AP50; CH100; AP100

Test of integrity of classical and alternate lytic pathways of complement. Such conditions are rare and present either with a predisposition to recurrent bacterial infections, especially meningococcal (C5-9, properdin) and pneumococcal infection (C1-4), or with increased susceptibility to immune complex diseases such as SLE (C1-4).

NB If you suspect this condition, we suggest that you discuss this with an Immunologist prior to requesting this assay.

Specimen requirements

Serum - 1ml


Price on application

Laboratory turnaround time

21 days

Laboratory method


Reference range/units

Normal >60% activity of normal control
Borderline 40 6o 60% of normal control
Abnormal <40% of normal control

Associated tests

Not applicable

Sample stability

<8 hours at RT (must be stored at -80ÂșC)

Shipping and storage

Sample needs to reach the Laboratory within 8 hours of venepuncture.

Patients with any form of meningococcal disease, particularly if recurrent, should be screened in convalescence with a CH100.

UKAS Accreditation status

This test is currently not accredited due to changes in method.

Further information and contact details

For further information, email

Last reviewed:22 May 2023