Ordering Guidance

The most appropriate primary assays to use as screening methods for complement deficiencies are COM / Complement, Total, Serum and AH50 / Alternative Complement Pathway, Functional, Serum. Abnormal results in one or the other, none, or both assays will help direct further testing. If total complement and AH50 are both normal but the suspicion of a complement deficiency remains, this test for the lectin pathway function is recommended. After the initial 3 pathways of complement functional status are evaluated, the analysis of individual components and regulators may uncover functional or quantitative defects in certain components.

This test is rarely useful when ordered in isolation.

As the heat-labile fraction of the immune system, complement activation in vitro has been a challenge for researchers and scientists. Because of the thermal instability of complement proteins, it is often necessary to repeat testing to rule out a possible pre-analytical issue with a sample type, real complement consumption, or dysregulation.

Specimen Required

Patient Preparation:

1. Specimen should not be collected earlier than 48 hours following plasma exchange.

2. Fasting is preferred.

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 plastic vial.

3. Freeze specimen within 30 minutes of centrifugation. Sample must be placed on dry ice if not frozen immediately.

Additional Information:

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.