Detecting deficiencies in the alternative pathway that can cause atypical-hemolytic uremic syndrome, dense deposit disease, and C3 glomerulonephritis
A second-tier test that aids in the differential diagnosis of thrombotic microangiopathies
This test should be performed prior to treatment initiation and in the absence of therapy with complement inhibitors, such as eculizumab or ravulizumab. Complement inhibitors will affect performance of these assays.
For evaluating patients with possible thrombotic microangiopathies (TMA), the recommended first-tier test is ADM13 / ADAMTS13 Activity and Inhibitor Profile, Plasma. This test should be a second-tier test for TMA.
For patients who have received eculizumab or need to monitor response to eculizumab therapy, the recommended test is ECUMP / Eculizumab Monitoring Panel, Serum. Soluble membrane attack complex (sMAC) should not be used as a standalone assay to monitor eculizumab efficiency.
Patient Preparation:1. Fasting preferred.2. Samples should not be collected earlier than 48 hours following plasma exchange.
1. Immediately after specimen collection, place the tube on wet ice.
2. Centrifuge; 1500 x g for 10 minutes at 4 degrees C and aliquot plasma into plastic vial.
3. Freeze specimen within 30 minutes.
2. Centrifuge at 4 degrees C and aliquot serum into 5 mL plastic vial.
As with all complement assays, proper sample handling is of utmost importance to ensure that the complement system is not activated before clinical testing.
C3HUS, C4HUS, FBCA, FHCA: Nephelometry
COM3: Automated Liposome Lysis Assay
AH503, C4D, CBB, SC5B9: Enzyme-Linked Immunosorbent Assay (ELISA)
FACTOR B COMPLEMENT ANTIGEN
< or =250 ng/mL
FACTOR H COMPLEMENT ANTIGEN
18.5 to 40.8 mg/dL
C4d COMPLEMENT ACTIVATION FRAGMENT
< or =9.8 mcg/mL
CBb COMPLEMENT ACTIVATION FRAGMENT
< or =1.6 mcg/mL
ALTERNATIVE COMPLEMENT, PATHWAY (AH50) FUNCTIONAL
> or =46% normal
An interpretive report will be provided.