Test Overview
Clinical Utility
Diagnosis of C7 deficiency. Investigation of a patient with an undetectable total complement level.
Method
Liposome immune lysis assay (LILA)
Analytical Platform
Advia XPT
Method Description
Activity of C7 is measured by mixing patient serum with a C7-deficient serum. The lytic activity of the serum mixture is tested against sensitized, labeled liposomes. If lysis occurs, the patient serum must be the source of the C7. The target liposomes are a commercial reagent (WAKO total complement CH50).
Result Included
C7 Complement, Functional
Specimen
Specimen Type
SerumContainers
Preferred Containers
Gold top (clot activator & gel)
Acceptable Containers
Red top (no additive)
Volume
Sample Volume
1.0 mL
Minimum Volume
0.5 mL
Patient Preparation
Fasting 12 hours preferred but not required.
Collection & Handling
Collection Instructions
1. Immediately after specimen collection, place the tube on wet ice and allow specimen to clot.
2. Centrifuge at 4 degrees C and aliquot serum into a plastic vial.
3. Within 30 minutes of centrifugation, freeze specimen. Specimen 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 sample is kept on ice before centrifugation, and immediately afterward, the serum is aliquoted and frozen.
Stability
| Frozen |
|---|
| 14 days |
Rejection Criteria
| Criteria | Specification |
|---|---|
| Lipemia | Gross |
Performance & Interpretation
Turnaround Time
8 days
Results
-
C7 Complement, FunctionalU/mL36 - 60
Comment
Low levels of complement may be due to inherited deficiencies, acquired deficiencies, or due to complement consumption (eg, as a consequence of infectious or autoimmune processes).
Absent C7 levels in the presence of normal C3 and C4 values are consistent with a C7 deficiency. Absent C7 levels in the presence of low C3 and C4 values suggest complement consumption.
As with all complement assays, proper specimen handling is of utmost importance to ensure that the complement system is not activated before clinical testing.>br>Absent (or low) C7 functional levels in the presence of normal C7 antigen levels should be replicated with a new serum specimen to confirm that C7 inactivation did not occur during shipping.
Referral Location
Out-of-Country
Interface & Setup
HL7 Interface Codes
| Order Code | Result Name | Result Codes | Units |
|---|---|---|---|
| C7FX S | C7 Complement, Functional, S | 63664 | U/mL |
Test Version
Last Updated
2025-11-11