Test Catalog

Test Id : C5B9

SC5b-9 Level Terminal Complement Complex, Plasma

Useful For
Suggests clinical disorders or settings where the test may be helpful

Detecting increased complement activation

Method Name
A short description of the method used to perform the test

Enzyme-Linked Immunosorbent Assay (ELISA)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

SC5b-9 Complement, P

Lists additional common names for a test, as an aid in searching

Terminal Complement Complex





membrane attack complex

Specimen Type
Describes the specimen type validated for testing

Plasma Na Cit

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation:

1. Fasting preferred.

2. Do not collect a specimen for the 48 hours following a plasma exchange.

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Plastic vial

Specimen Volume: 1.5 mL

Collection Instructions:

1. Immediately after specimen collection, place the tube on wet ice.

2. Centrifuge between 1000-2000 x g for 10 minutes at 4 degrees C and aliquot plasma into plastic vial.

3. Freeze specimen within 30 minutes.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis OK
Gross lipemia Reject
Gross icterus OK

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen 14 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

Detecting increased complement activation

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The complement system membrane attack complex (MAC) is formed by the C5b fragment along with C6, C7, C8 and several C9 molecules. This complex is recognized by multiple names, including MAC, terminal complement complex and C5b-9. Laboratory tests measure the amount of soluble C5b-9 (sC5b-9) complex. The formation of C5b-9 and sC5b-9 is a consequence of activation of the complement system by either the classical, lectin, or alternative pathways. Therefore, measurement of the sC5b-9 complex can be used as a surrogate marker of terminal complement activation via all complement pathways.


Elevated concentrations of C5b-9 are associated with the development of transplant-associated thrombotic microangiopathy (TA-TMA), a complication of hematopoietic stem cell transplant.(1-3) Patients with higher sC5b-9 concentrations at baseline may require the use of higher doses of eculizumab to treat TA-TMA,(4) especially in children. Because of this association, measurement of sC5b-9 before transplant as part of a diagnostic evaluation and then repeat measurements during therapy have been proposed as tools to follow-up patients.(5) Importantly, while the elevation of sC5b-9 has shown very high sensitivity for TA-TMA, it has shown only a modest specificity, ranging from 40% to 50%, and the increased sC5b-9 may be found in other transplant complications as well as several other conditions where complement activation may occur: immune-complex disease, infection, atypical hemolytic uremic syndrome, C3 glomerulopathies, etc. A panel of complement tests, such as AHUSD / Atypical Hemolytic Uremic Syndrome Complement Panel, Serum and Plasma, may provide additional information on the extent of the complement activation, along with the information of which pathway is most dysregulated.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

< or =250 ng/mL

Provides information to assist in interpretation of the test results

Elevated concentrations of soluble C5b-9 suggest recent or ongoing activation of the complement system, while normal and low concentrations suggest that the complement system has not been excessively activated.


A panel of complement tests may be clinically indicated to further identify the extent of the complement activation, along with the information of which pathway is most dysregulated.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

As with all complement assays, proper sample handling is of utmost importance to ensure that the complement system is not activated before clinical testing.


Measurement of soluble C5b-9 should be ideally performed prior to treatment initiation and in the absence of therapy with complement inhibitors, such as eculizumab and ravulizumab. Complement inhibitors, such as eculizumab and ravulizumab, may affect performance of this assay.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Qi J, Wang J, Chen J, Su J, et al: Plasma levels of complement activation fragments C3b and sC5b-9 significantly increased in patients with thrombotic microangiopathy after allogeneic stem cell transplantation. Ann Hematol. 2017 Nov;96(11):1849-1855

2. Horvath O, Kallay K, Csuka D, et al: Early increase in complement terminal pathway activation marker sC5b-9 Is predictive for the development of thrombotic microangiopathy after stem cell transplantation. Biol Blood Marrow Transplant. 2018 May;24(5):989-996

3. Mezo B, Horvath O, Sinkovits G, Veszeli N, Krivan G, Prohaszka Z: Validation of early increase in complement activation marker sC5b-9 as a predictive biomarker for the development of thrombotic microangiopathy after stem cell transplantation. Front Med (Lausanne). 2020 Oct 6;7:569291

4. Jodele S, Dandoy CE, Lane A, et al: Complement blockade for TA-TMA: lessons learned from a large pediatric cohort treated with eculizumab. Blood. 2020 Mar 26;135(13):1049-1057

5. Young JA, Pallas CR, Knovich MA: Transplant-associated thrombotic microangiopathy: theoretical considerations and a practical approach to an unrefined diagnosis. Bone Marrow Transplant. 2021 Aug;56(8):1805-1817

Method Description
Describes how the test is performed and provides a method-specific reference

Microtiter plates are coated with monoclonal antibody specific to the C9 ring of the soluble C5b-9 (sC5b-9) complex. Controls, standards, and patient samples are exposed to the plate. After washing the plate, a horseradish peroxidase-conjugated anti-sC5b-9 complex antibody is added followed by a substrate to initiate color change.(Package insert: MicroVue SC5b-9 Plus EIA Kit. Quidel Corporation; 0980EN02, 09/2021)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Tuesday, Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

3 to 5 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

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  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
C5B9 SC5b-9 Complement, P 93244-2
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
616921 SC5b-9 Complement, P 93244-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports

Test Update Resources

Change Type Effective Date
New Test 2022-07-07