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Test Code AH50 Complement, Alternate Pathway (AH50), Functional, Serum

Reporting Name

Complement, Alternate Path, Func, S

Useful For

Investigation of suspected alternative pathway complement deficiency, atypical hemolytic uremic syndrome, C3 glomerulonephritis, dense-deposit disease

Specimen Required

Patient Preparation: Patient should be fasting.

Collection Container/Tube: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Immediately after drawing the specimen, place the tube on wet ice.

2. Spin down and separate serum from clot.

3. Freeze specimen within 30 minutes.

Seattle Children's Hospital Note:

Collect 2.0 mL whole blood in a Red top.

Specimen Type

Serum Red

Specimen Minimum Volume

0.2 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Frozen 14 days

Day(s) and Time(s) Performed


Performing Laboratory

Mayo Medical Laboratories in Rochester

Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Method Description

For quantitation of alternative pathway function, immunoassay strips are coated with specific activators of the alternative pathway. Patient serum is diluted in diluent containing a specific blocker to ensure that only the alternative pathway is activated. During the incubation of the diluted patient serum in the wells, complement is activated by the specific coating generating a terminal complement complex (C5b-9, membrane attack complex: MAC). Strips are washed and the MAC is detected with a specific alkaline phosphatase-labeled antibody to the neoantigen expressed during MAC formation. After additional washing, color generation is accomplished by incubation with alkaline phosphatase substrate solution. The amount of complement activation correlates with the color intensity and is measured in terms of absorbance (optical density).(Nordin JG, Truedsson L, Sjoholm A: New procedure for detection of complement deficiency by ELISA, J Imm Methods 1993;166:655-668)

Reference Values

≥46% normal

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
AH50 Complement, Alternate Path, Func, S 74520-8


Result ID Test Result Name Result LOINC Value
88676 Complement, Alternate Path, Func, S 74520-8

Reject Due To


Mild OK; Gross OK


Mild OK; Gross OK


Mild OK; Gross OK


Serum gel tube