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Epic Code LAB2111135 Mycophenolic Acid, Serum

Additional Codes

Mayo Code: MPA

Epic Code: LAB 2111135

Interface Order Alias: 11143

Cerner code: 1563

Reporting Name

Mycophenolic Acid, S

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Clinical Information

Mycophenolate mofetil (CellCept) is a new immunosuppressive agent useful in organ transplantation. It is approved for use in renal, hepatic, and cardiac transplants. When mycophenolate mofetil enters the blood, it is immediately metabolized to the active drug, mycophenolic acid (MPA), which inhibits inosine monophosphate dehydrogenase and interferes with the de novo pathway of guanosine nucleotide synthesis selectively in lymphocytes. MPA inhibits proliferative responses of T and B lymphocytes to both mitogenic and allo-specific stimulation. MPA acts in the same fashion as azathioprine, and MPA is suggested as replacement therapy for azathioprine. The drug is deactivated by the hepatic enzyme, uridine diphosphate glucuronosyltransferase to form MPA glucuronide (MPA-G).

 

The principle clinical problem encountered in MPA therapy is excessive immunosuppression, which predisposes the patient to systemic infection. Measurement of the blood level of MPA and MPA-G can be useful to guide therapy.

 

Monitoring is recommended from immediately after transplant to 3 weeks after therapy is initiated to evaluate dosing adequacy. Additional monitoring is indicated if the MPA level is not in the therapeutic range or if a major change in health status occurs.

Useful For

Monitoring therapy to ensure adequate blood levels and avoid over-immunosuppression

Specimen Type

Serum Red


Specimen Required


Patient Preparation: Collect specimen just prior to next dose (ie, trough)

Container/Tube: Red top

Specimen Volume: 1 mL


Laboratory Test Directory Note:

COLLECTION NOTE: Volumes listed are in serum or plasma, draw approximately 2 1/2 times the requested volume in whole blood.

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  21 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Day(s) Performed

Monday through Sunday

Reference Values

MYCOPHENOLIC ACID (MPA)

1.0-3.5 mcg/mL

 

MPA GLUCURONIDE

35-100 mcg/mL

Interpretation

Trough steady-state serum levels of mycophenolic acid (MPA) (>2 weeks at the same dose) in the range of 1.0 to 3.5 mcg/mL indicate adequate therapy. MPA glucuronide (MPA-G) levels in the range of 35 to 100 mcg/mL indicate that the patient has normal uridine diphosphate glucuronosyltransferase (UGT) metabolic capacity. MPA-G levels are typically in the range of 100 to 250 mcg/mL during the 2 weeks following transplantation. MPA-G typically decreases after this initial post-transplant phase.

 

Trough steady-state serum MPA levels over 4.0 mcg/mL indicate that the patient is over-immunosuppressed and susceptible to systemic infections. Decreased dosages may be indicated in these cases.

 

Low MPA levels and high MPA-G levels suggest that the patient has an active UGT metabolic capability; higher doses may be required to maintain therapeutic levels of MPA. Some patients have a high UGT metabolic capacity. These patients may require 1 gram or more 3 times a day to maintain trough serum MPA levels in the range of 1.0 mcg/mL to 3.5 mcg/mL. They are likely to have MPA-G levels over 100 mcg/mL. MPA-G is inactive; MPA-G levels only describe the patient's metabolic status.

 

Patients who have low UGT conjugating capability may become over-immunosuppressed, indicated by a trough steady-state serum MPA level over 4.0 mcg/mL and an MPA-G level below 40 mcg/mL. Dose reduction or interval prolongation is indicated in this case.

Cautions

Correct interpretation requires a trough serum specimen (just before the next regular dose). Specimens collected at other times in the dosing cycle are likely to have higher mycophenolic acid levels. In these cases, the reference range does not apply.

Clinical Reference

1. Moyer TP, Shaw LM: Therapeutic drug monitoring. In: Burtis CA, Ashwood ER, Bruns DE. Tietz Textbook of Clinical Chemistry. 4th ed. WB Saunders Company; 2005:1237-1285

2. Rifai N, Horvath AR, Wittwer CT, eds: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Method Description

Liquid chromatography-tandem mass spectrometry is used to quantify the serum concentration of mycophenolic acid (MPA) and MPA glucuronide (MPA-G). The test involves direct measurement of serum for MPA and MPA-G.(Unpublished Mayo method)

Report Available

Same day/1 to 3 days

Test Classification

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

80180

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MPA Mycophenolic Acid, S 87432-1

 

Result ID Test Result Name Result LOINC Value
15226 Mycophenolic Acid 23905-3
15227 MPA Glucuronide 23906-1

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Renal Diagnostics Test Request (T830)

-Therapeutics Test Request (T831)