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Test Code MTREX METHOTREXATE LEVEL [LAB481]

Important Note

Interpretive Data: 

Specimens from patients who have received carboxypeptidase can contain a hydrolysis fragment of MTX (DAMPA) that cross-reacts with the methotrexate antibody used in this immunoassay.

Because enzyme immunoassay interference can result in overestimation of serum MTX concentrations immediately after administration of carboxypeptidase enzyme treatment (glucarpidase), it may be helpful to measure MTX after the glucarpidase dosing using a more specific assay (e.g. LC-MS/MS). The LC-MS/MS testing for MTX in these cases can be obtained by sendout to Mayo Medical Laboratories for "Methotrexate Post Glucarpidase, Serum." 

Performing Laboratory

Iowa Methodist Medical Center

Clinical Testing | Pathology Laboratory

Test Performance

Performed: 

Daily
24 hours a day

 

Analytical Time: 

2 hours

Methodology

Immunoassay

Specimen Requirements

Preferred Collection Container: 

Green (Lithium Heparin)
No Gel

 

Also Acceptable Collection Container: 

Red (No Additive)

 

Collection Information: 

Do not use gel separator tubes.

 

Transport Information: 

2.0 mL blood/0.6 mL plasma or serum

 

Minimum Sample Volume: 

0.4 mL blood/0.2 mL plasma or serum

Specimen Stability

Refrigerated Stability: 

3 days

 

Frozen Stability: 

6 months

 

Ambient Stability: 

12 hours

CPT Coding

80204