Clinical background:
The CH50 and AP100 assays are ran conjunctively and test complement function. The use of these assays should be limited to the investigation of suspected complement deficiency or the monitoring of complement blocking medications. Any patient with recurrent pyogenic infections or meningococcal disease should be screened, as there is a possibility of a complement deficiency. Patients with atypical lupus may rarely show a defect in CH50 and complement components C1 or C2.
Specimen container paediatric:
Serum-Plain tube
Specimen container adult:
Serum-SST
Minimum volume paediatric:
2 ml
Minimum volume adult:
2 ml
Special requirements:
Samples MUST be separated within 4 hours of venesection. Please ensure that the sample arrives in the laboratory as soon as possible after being taken.
Freq analysis:
Weekly
Add on test:
These tests cannot be added on without discussion with the Immunology team at [email protected]
Interpretation:
Low/Absent complement function may be caused by complement consumption, for example during ongoing infection or inflammation, by genetic complement deficiencies or by the use of complement targeting medication e.g. Eculizumab.
Results can also be low due to incorrect sample transport.
The Immunology team can advise on abnormal results and any further testing which may be useful.
Reference ranges:
Alternative Pathway: 30-113%
CH50: 41.68-95.06 U/ml
Other info:
The Alternative Pathway assay is an enzyme immunoassay and the CH50 assay is a liposomal assay which uses a change in absorbance to determine complement activity.