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Test Code ECUMP Eculizumab Monitoring Panel, Serum

Useful For

Therapeutic drug monitoring of eculizumab

Profile Information

Test ID Reporting Name Available Separately Always Performed
C5FX C5 Complement, Functional, S Yes Yes
C5AG2 C5 Complement, Antigen, S Yes, (Order C5AG) Yes
INT86 ECUMP Interpretation No Yes

Method Name

C5AG2: Nephelometry

C5FX: Automated Liposome Lysis Assay

Reporting Name

Eculizumab Monitoring Panel, S

Specimen Type

Serum Red


Specimen Required


Patient Preparation:

1. Fasting preferred

2. Recommended timeframe for the blood draw is a trough, or immediately prior to next intravenous infusion.

Specimen Type: Serum

Collection Container/Tube: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1.5 mL

Collection Instructions:

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

2. Spin down and separate serum from clot.

3. Freeze specimen within 30 minutes.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Frozen 14 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

Mild OK; Gross reject

Icterus

NA

Other

Serum gel tube

Clinical Information

Eculizumab (Soliris, Alexion Pharmaceuticals) is a humanized hybrid monoclonal antibody (IgG2/IgG4) that blocks complement C5 cleavage, thereby preventing the activation of the proinflammatory effects of C5a and the cytolytic effects of the membrane attack complex (MAC) formed by C5b-C9. It is FDA-approved for atypical hemolytic uremic syndrome,(1) paroxysmal nocturnal hemoglobinuria,(2) and neuromyelitis optica, and also prescribed for other conditions such as C3 glomerulopathies.(3) The dosing regimen for an average adult may vary from 300 to 1200 mg intravenously every 2 weeks during the maintenance stages, according to the condition for which the drug is prescribed. Therapy efficacy may be monitored by measuring efficiency of complement blockade.(4) Eculizumab will affect complement function assays that rely on the formation of the MAC to generate cell lysis. Although CH50 and sMAC have been recommended for eculizumab monitoring, the measurement of C5 function and C5 antigen will more specifically indicate the impact of eculizumab on the complement system blockage and may help guide the next dose of the drug.

 

This panel measures the pharmacodynamics effects of eculizumab on the complement system.

Reference Values

C5 COMPLEMENT ANTIGEN

10.6-26.3 mg/dL

 

C5 COMPLEMENT FUNCTIONAL

29-53 U/mL

Interpretation

The panel will measure the pharmacodynamic effects of eculizumab on the complement system. Total complement function (CH50), alternative pathway function (AH50), and C5 function assays will be decreased to a similar extent in the presence of eculizumab. The function of C5 may be completely absent when eculizumab is present at therapeutic concentrations. C5 antigen, on the other hand, will be normal or elevated. C5 complement function drops on average 30% with 25 mcg/mL of eculizumab, and 70% with 50 mcg/mL. In the presence of 100 mcg/mL of eculizumab in serum, there is on average 20% residual C5 function.

 

Decreased C5 function in the presence of normal or elevated C5 antigen concentrations suggests eculizumab is partially blocking C5 activity.

 

Absent C5 function in the presence of normal or elevated C5 antigen concentrations suggests eculizumab is completely blocking C5 activity.

 

Normal C5 function in the presence of normal or elevated C5 antigen concentrations suggests eculizumab concentration is not sufficient to block C5 activity.

 

If C5 function and C5 antigen concentrations are all decreased, it may be due to a secondary consumption process, poor hepatic synthesis of complement proteins or C5 deficiency. Clinical correlation recommended. If indicated, resubmit samples to confirm results.

Cautions

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

 

This panel of assays will not quantitate eculizumab concentrations.

 

This panel will not measure the soluble membrane attack complex (sMAC).

Supportive Data

In a Mayo Clinic study(5) with samples from individual subjects with normal complement activity defined by the CH50 assay and spiked with varying concentrations of eculizumab, there was a significant decrease in CH50, AH50, and C5 functional results with eculizumab. Considering that the therapeutic target concentrations are expected to be above 50 mcg/mL, the results showed that eculizumab is partially blocking the complement cascade at 25 mcg/mL, with a complete blockage for C5 functional at 100 mcg/mL in individuals.

Clinical Reference

1. Wong EK, Goodship TH, Kavanagh D: Complement therapy in atypical haemolytic uraemic syndrome (aHUS). Mol Immunol 2013;56:199-212

2. Rother RP, Rollins SA, Mojcik CF, et al: Discovery and development of the complement inhibitor eculizumab for the treatment of paroxysmal nocturnal hemoglobinuria. Nat Biotechnol 2007;25:1256-1264

3. Zuber J, Le Quintrec M, Krid S, et al: Eculizumab for atypical hemolytic uremic syndrome recurrence in renal transplantation. Am J Transplant 2012;12:3337-3354

4. Volokhina EB, van de Kar NC, Bergseth G, et al: Sensitive, reliable and easy-performed laboratory monitoring of eculizumab therapy in atypical hemolytic uremic syndrome. Clin Immunol 2015;160(2):237-243

5. Andreguetto B, Murray D, Snyder M, et al: The impact of eculizumab in complement assays. Mol Immunol 2015;67:119-120

Method Description

C5 Complement, Functional:

C5 complement activity is measured by mixing patient serum with a C5-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 C5. The target liposomes are a commercial reagent (WAKO total complement CH50), and the assay is performed on a Hitachi 912.(Unpublished Mayo information; Yamamoto S, Kubotsu K, Masaaki K, et al: Automated homogeneous liposome-based assay system for total complement activity. Clin Chem 1995;41:586-590)

 

C5 Complement Antigen:

Anti-C5 reagent is added to patient serum and quantitated on a Dade Behring BN II analyzer by fixed-time kinetic nephelometry.(Unpublished Mayo method; instruction manual: Siemens Nephelometer II, Version 2, 1999)

Day(s) and Time(s) Performed

Varies

Analytic Time

2 days

Specimen Retention Time

14 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

See Individual Test IDs

CPT Code Information

86160-Complement; antigen, each component

86161-Complement; functional activity, each component

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ECUMP Eculizumab Monitoring Panel, S In Process

 

Result ID Test Result Name Result LOINC Value
C5FX C5 Complement, Functional, S 60472-8
C5AG2 C5 Complement, Antigen, S 4505-4
INT86 ECUMP Interpretation In Process