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HelpTest Code AH50 Alternative Complement Pathway, Functional, Serum
Reporting Name
Alternative Complement Path Func, SUseful For
Investigation of suspected alternative pathway complement deficiency, atypical hemolytic uremic syndrome, C3 glomerulonephritis, and dense-deposit disease
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Serum RedOrdering Guidance
COM / Complement, Total, Serum and this test are the most appropriate primary assays to use as screening methods for complement deficiencies. Abnormal results in one or the other, neither or both assays will help direct further testing.
This test is rarely useful when ordered in isolation.
Specimen Required
Patient Preparation: Patient should be fasting.
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Immediately after specimen collection, place the tube on wet ice.
2. After sample has clotted on wet ice, centrifuge at 4° C and aliquot serum into a plastic vial.
3. Freeze specimen within 30 minutes of centrifugation. Sample must be placed on dry ice if not frozen immediately.
NOTE: If a refrigerated centrifuge is not available, it is acceptable to use a room temperature centrifuge, provided the specimen is kept on ice before centrifugation, and immediately afterward, the serum aliquoted and frozen.
Specimen Minimum Volume
0.2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Frozen | 14 days |
Reference Values
≥46% normal
Day(s) Performed
Monday, Thursday
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
86161
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| AH50 | Alternative Complement Path Func, S | 74520-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 88676 | Alternative Complement Path Func, S | 74520-8 |
Interpretation
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.
Clinical Reference
1. Frank MM. Medical intelligence current concepts: complement in the pathophysiology of human disease. N Engl J Med. 1987;316(24):1525-1530. doi:10.1056/NEJM198706113162407
2. Thurman JM, Holers VM. Brief reviews: the central role of the alternative complement pathway in human disease. J Immunol. 2006;176(3):1305-1310. doi:10.4049/jimmunol.176.3.1305
3. Frank MM. Complement deficiencies. Pediatr Clin North Am. 2000;47(6):1339-1354. doi:10.1016/s0031-3955(05)70274-1
4. Go RS, Winters JL, Leung N, et al. Thrombotic microangiopathy care pathway: A consensus statement for the Mayo Clinic Complement Alternative Pathway-Thrombotic Microangiopathy (CAP-TMA) Disease-Oriented Group. Mayo Clin Proc. 2016;91(9):1189-1211. doi:10.1016/j.mayocp.2016.05.015
5. Willrich MAV, Andreguetto BD, Sridharan M, et al. The impact of eculizumab on routine complement assays. J Immunol Methods. 2018;460:63-71. doi:10.1016/j.jim.2018.06.010
Report Available
3 to 5 daysMethod Name
Enzyme-Linked Immunosorbent Assay (ELISA)
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.