Search

Methotrexate
Methodology: 
Immunoassay

Performed: 
Daily
24 hours a day

Analytical Time: 
2 hours

Testing Laboratory: 
Iowa Methodist Medical Center

Laboratory Section: 
Core Laboratory

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." 

Methotrexate
Preferred Collection Container: 
Green NO Gel (Lithium Heparin)

Also Acceptable Collection Container: 
Red (No Additive)

Collection Information: 
Do not use gel separator tubes. Collect blood in a green no gel lithium heparin tube or serum red top tube.

Transport Information: 
Centrifuge and aliquot 0.6 plasma or serum into a transport tube.

Minimum Sample Volume: 
0.2 mL plasma or serum (approximately 0.4 mL of whole blood based upon a normal patient hematocrit)

Stability
Refrigerated Stability: 
3 days

Frozen Stability: 
6 months

Ambient Stability: 
12 hours

Methotrexate
Sunquest Order Code: 
MTREX

Epic Number: 
LAB481

CPT Code: 
80204

Methotrexate
Modified: 
9/27/2013 10:21:38 AM