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HelpTest Code RAVMP Ravulizumab Monitoring Panel, Serum
Ordering Guidance
To measure only serum concentration of ravulizumab, order RAVU / Ravulizumab, Serum.
Specimen Required
Patient Preparation:
1. Fasting preferred.
2. Suggest discontinuing natalizumab at least 4 weeks prior to testing for ravulizumab quantitation in serum. Patient should consult the healthcare provider who prescribed this drug to determine if discontinuation is an option. If not, ok to proceed with testing while taking natalizumab.
Supplies: Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: 2 Plastic vials
Specimen Volume: 2 mL in 2 plastic vials, each vial containing 1 mL
Collection Instructions:
1. Draw blood immediately before next scheduled dose.
2. Immediately after specimen collection, place the tube on wet ice.
3. After sample has clotted on wet ice, centrifuge at 4° C and aliquot serum into two 5 mL plastic vials.
4. Freeze specimen within 30 minutes of centrifugation. Sample must be placed on dry ice if not frozen immediately.
Useful For
Monitoring of complement blockage by ravulizumab
Assessing the response to ravulizumab therapy
Assessing the need for dose escalation
Evaluating the potential for dose deescalation or discontinuation of therapy in remission states
Monitoring patients who need to be above a certain ravulizumab concentration in order to improve the odds of a clinical response for therapy optimization
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| RAVU | Ravulizumab, S | Yes | Yes |
| RAVUM | Ravulizumab Complement Blockage, S | No | Yes |
| RAVIN | Ravulizumab Interpretation, S | No | Yes |
Method Name
RAVUM: Enzyme-Linked Immunosorbent Assay (ELISA)
RAVU: Liquid Chromatography Tandem Mass Spectrometry, High Resolution Accurate Mass (LC-MS/MS HRAM)
Reporting Name
Ravulizumab Monitoring Panel, SSpecimen Type
SerumSerum Red
Specimen Minimum Volume
1 mL in 2 plastic vials, each vial containing 0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Frozen | 14 days | |
| Serum Red | Frozen | 14 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | OK |
Clinical Information
Ravulizumab (Ultomiris, 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.
The dosing regimen for ravulizumab is weight-based, and after a loading dose schedule, the maintenance therapy requires administration intravenously every 8 weeks. Therapy efficacy may be monitored by measuring efficiency of complement blockade. Ravulizumab will affect complement function assays that rely on the formation of the MAC to generate cell lysis. Validation studies performed by Mayo Clinic show that the alternative pathway (AH50) enzyme-linked immunosorbent assay is the most helpful of the complement tests to monitor efficacy of the complement blockage by ravulizumab. Ravulizumab serum concentrations greater than 200 mcg/mL inhibited the AH50 activity completely, and undetectable activity was measured at all subsequent tested concentrations up to 1000 mcg/mL.(1)
Some patients whose serum concentrations persist above therapeutic targets with complete complement blockade could benefit from dose deescalation or prolonged infusion intervals. Therapeutic drug monitoring of ravulizumab could result in cost-savings and improved quality of life if target therapeutic concentrations can be achieved with complete complement system blockage at less frequent dosing intervals.
Reference Values
RAVULIZUMAB COMPLEMENT BLOCKAGE:
≥46% normal
RAVULIZUMAB:
Lower limit of quantitation =5.0 mcg/mL
>175 mcg/mL: Therapeutic concentration for paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome
Interpretation
Target trough therapeutic concentrations (immediately before next infusion) of ravulizumab are expected to be above 175 mcg/mL for paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Pharmacodynamic studies of complement blockage may also be recommended for patients undergoing therapy.
For the complement blockage monitoring of ravulizumab:
-When ravulizumab is present in serum at concentrations around 50 mcg/mL, the results range from 20% to 29% of normal.
-When ravulizumab concentrations are around 100 mcg/mL, the results range from below 10% to 13% of normal.
-When ravulizumab concentrations are greater than 200 mcg/mL, the results are below the limit of quantitation of the assay (<10% of normal).
Day(s) Performed
Varies
Report Available
3 to 10 daysSpecimen Retention Time
14 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
80299
86161
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| RAVMP | Ravulizumab Monitoring Panel, S | 101923-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 609500 | Ravulizumab Complement Blockage, S | 74520-8 |
| 609420 | Ravulizumab, S | 97184-6 |
| 619952 | Ravulizumab Interpretation | 59462-2 |