Complement – Alternative Pathway (AH50) Functional, Serum
Test Overview
Clinical Utility
Investigation of suspected alternative pathway complement deficiency, atypical hemolytic uremic syndrome, C3 glomerulonephritis, dense-deposit disease
Method
Enzyme-linked immunosorbent assay (ELISA)
Method Description
The Wieslab enzyme-linked immunosorbent assay (ELISA) complement assay for the alternative pathway combines principles of the hemolytic assay for complement activation with the use of labeled antibodies specific for neoantigens produced as a result of complement activation. The micro titer plate strips are coated with lipopolysaccharide (LPS). Patient serum is diluted in diluent containing specific blocker to ensure that only the alternative pathway is activated. During the first incubation, the diluted patient serum in the wells is activated by the coating. The wells are then washed and C5b-9 (MAC) is detected with a specific alkaline phosphatase labeled antibody to the neoantigen expressed during MAC formation. After a final wash, an alkaline phosphatase substrate is added. The amount of alternative pathway complement activity correlates with the color intensity of the solution and is measured in terms of absorbance (optical density: OD).(Frazer-Abel A, Sepiashvili L, Mbughuni MM, Willrich MA: Overview of laboratory testing and clinical presentations of complement deficiencies and dysregulation. Adv Clin Chem. 2016;77:1-75. doi: 10.1016/bs.acc.2016.06.001)
Result Included
Complement - Alternative Pathway (AH50) Functional
Aliases/Synonyms
aHUS
Specimen
Specimen Type
SerumContainers
Collection Containers
Red top (no additive). Avoid gel separator tubes.
Volume
Sample Volume
1 mL
Minimum Volume
0.2 mL
Specimen Comment
Avoid gel separator tubes
Patient Preparation
Fasting
Collection & Handling
Collection Instructions
Collect a fasting sample.
Handling Information
Immediately after specimen collection, place the tube on wet ice. Centrifuge at 4°C and aliquot serum into plastic vial. Freeze specimen within 30 minutes.
Stability
| Frozen |
|---|
| 14 days |
Rejection Criteria
| Criteria | Specification |
|---|---|
| Specimen | Received not frozen |
Performance & Interpretation
Turnaround Time
12 Days
Results
-
Complement - Alternative Pathway (AH50) Functional% of norm≥46
Comment
Absent complement alternative pathway (AH50) in the presence of a normal total hemolytic complement (CH50) suggests an alternative pathway component deficiency.
Normal AH50 with absent CH50 suggests an early (C1, C2, C4) classic pathway deficiency.
Absent AH50 and CH50 suggests a late (C3, C5, C6, C7, C8, C9) component deficiency or complement consumption.
Absent AH50 and CH50 in the presence of a normal C3 and C4 suggests a late (C5, C6, C7, C8, C9) component deficiency.
Normal CH50 and AH50 in the presence of recurrent infection and continued suspicion of complement deficiency, suggest testing for lectin pathway function.
Referral Location
Out-of-Country
Interface & Setup
HL7 Interface Codes
| Order Code | Result Name | Result Codes | Units |
|---|---|---|---|
| AH50F S | Complement, Alternate Path, Func, S | 63358 | % of norm |
Test Version
Last Updated
2021-01-15