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Order Code RAVU Ravulizumab, Serum


Ordering Guidance


To measure only serum concentration of ravulizumab, order RAVU / Ravulizumab, Serum.

 

To measure the impact of ravulizumab on complement activity and its effect on complement blockage, order RAVMP / Ravulizumab Monitoring Panel, Serum, which measures the alternative pathway function.



Specimen Required


Patient Preparation: Consider discontinuing natalizumab at least 4 weeks prior to specimen collection. Patient should consult the healthcare provider who prescribed this medication to determine if discontinuation is an option. If not, ok to proceed with testing while taking natalizumab.

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 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 specimen has clotted on wet ice, centrifuge at 4° C and aliquot serum into a plastic vial.

4. Freeze specimen within 30 minutes of centrifugation. Specimen must be placed on dry ice if not frozen immediately.


Useful For

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

 

This test is not useful as the sole basis for a diagnosis or treatment decisions

Method Name

Liquid Chromatography Tandem Mass Spectrometry, High Resolution Accurate Mass (LC-MS/MS HRAM)

Reporting Name

Ravulizumab, S

Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen (preferred) 28 days
  Ambient  28 days
  Refrigerated  28 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus OK

Reference Values

Lower limit of quantitation=5.0 mcg/mL

 

>175 mcg/mL-Therapeutic concentration for paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome

Method Description

Monoclonal immunoglobulin rapid accurate mass measurement (miRAMM) is used to quantify intact light chains from the therapeutic monoclonal antibodies (mAb) in human serum. Briefly, IgG4 along with IgG4 monoclonal or therapeutics are extracted from patient sample using a human IgG4 affinity matrix that contains a 12-kDa llama antibody fragment recognizing human IgG4. Wash steps significantly reduce background and remove all non-IgG4s as well as other proteins from the sample. After elution, the mixture undergoes a reduction step to release the light chains from the heavy chains by reducing the disulfide bonds that keep them together. While full scan data is collected, targeted selected ion monitoring occurs for the +10, 11, and 12 charge states for the eculizumab/ravulizumab light chain along with the +11-charge state for natalizumab, the surrogate internal standard. Multiple isotopes of each charge state are combined to be used for quantitation. A standard curve of the pharmaceutical mAb spiked into normal human serum is used for quantitation.(Unpublished Mayo method)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

80299

Day(s) Performed

Wednesday