Ordering Recommendation

Use to monitor complement blockage in patients treated with C5 inhibitor drugs.

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Plain red.

Specimen Preparation

Separate serum from cells ASAP or within 2 hours of collection. Transfer 2.0 mL serum to an ARUP standard transport tube and freeze immediately. (Min: 2.0 mL)

Storage/Transport Temperature

CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.

Unacceptable Conditions

Specimens received refrigerated, ambient, lipemic specimens, or grossly hemolyzed specimens. Serum separator tubes. Specimens collected using calcium-binding anticoagulants (i.e., EDTA, ACD).


Refer to individual components.


Quantitative Turbidimetric/Quantitative Radial Immunodiffusion


Tue, Fri


1-9 days

Reference Interval

Test Number
Reference Interval
  Complement Activity, Total Turbidimetric 38.7-89.9 U/mL
  Complement C5, Concentration 7-20 mg/dL
  Alternative Complement Pathway Activity 31 percent normal or greater
  Complement C5, Functional 23.0 U/mL or greater

Interpretive Data

Complement Activity, Total Turbidimetric Low: 38.6 U/mL or less 
Normal: 38.7-89.9 U/mL 
High: 90.0 U/mL or greater
Complement C5, Functional Low: 22.9 U/mL or less
Low-Normal: 23.0-28.3 U/mL
Normal: 28.4 U/mL or greater
Alternative Complement Pathway Activity See Report
C5 Inhibitors Drug Monitoring Pan Interp Patients treated with C5 inhibitors may show decreased/absent activity in total complement functional assay (CH50), alternative pathway functional assay (AH50), and C5 functional assay with normal or elevated C5 protein concentrations. Normal CH50, AH50, or C5 functional activity with normal or elevated C5 protein concentrations indicate inadequate complement blockage. Serial measurements are recommended when monitoring treatment efficacy. Decreases in both C5 concentration and C5 functional activity suggests a secondary consumption process or C5 deficiency. Repeat testing using a new specimen is suggested if in vitro complement activation and consumption of components due to conditions of collection, transport, and/or handling is suspected.

Compliance Category

Laboratory Developed Test (LDT)


Hotline History


CPT Codes

86160; 86161 x2; 86162


Component Test Code* Component Chart Name LOINC
0050156 Complement C5, Concentration 4505-4
2005374 Alternative Complement Pathway Activity 74520-8
3002576 Complement Activity, Total Turbidimetric 4532-8
3005962 Complement C5, Functional 60472-8
3006097 C5 Inhibitors Drug Monitoring Pan Interp 48767-8
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • AH50
  • anti-C5
  • C5 inhibitor
  • CH50 total
  • Complement blocking
  • Complement C5
  • Complement C5 functional
  • Complement monitoring
  • concentration
  • Eculizumab
  • Ravulizumab
C5 Inhibitors Drug Monitoring Panel