Laboratory Test Information Guide

Details for Methotrexate,Plasma/Serum

Test Name: Methotrexate,Plasma/Serum
Alternate Name(s):  
Laboratory: Core
Specimen Type:  4.5 mL Green (Lithium Heparin) top Vacutainer tube

Serum Gold or Red Vacutainer tubes are also acceptable

Pediatric:
0-2 years: Red 0.5 Microtainer tube
2-10 years 2 mL Red top tube
Collection Information: NOTE: NOTE: LABORATORY ANALYZER IS DOWN FOR MAINTENANCE FROM 0000 to approximately 0300h EXPECT DELAYS DURING THIS TIME.

Collect blood aseptically in a Vacutainer tube.

Minimum volume required is 3 mL of serum/plasma.


Collected according to dosing protocol.
Requisition: GENERAL LABORATORY REQUISITION
Test Schedule: As required
Turnaround time from when specimen
is received in testing laboratory:
 
Routine
4 hours
Stat
1 hour
 
Reference Range: 
High-risk Concentrations for toxicity (after high dose methotrexate):
24 hrs. post dose:
>10 µmol/L
48 hrs. post dose:
>1 µmol/L
72 hrs. post dose:
>0.2 µmol/L
Effective Date: 2012-03-01
Revised Date: 2018-04-05
Critical Value:  
Interpretive Comments: Antineoplastic chemotherapeutic agent. A clear relationship between serum concentration and therapeutic efficacy has not been clearly defined. Serum concentration monitoring has had a significant impact on drug-related toxicity. It is important that patients at high risk for toxicity be identified within 48 hrs. after initiation of methotrexate administration, since methotrexate toxicity may not be reversible if adequate leucovorin rescue is delayed for more than 42-48 hrs.
Special Processing:  
Comments: Specimens from patients who have received glucarpidase (carboxypeptidase G2) as a high does methotrexate rescue therapy should not be tested by the Enzyme Immunoassay due to interference.
Method of Analysis: Enzyme Immunoassay
Critical Information Required:  
Storage & Shipment:  
System Codes: 
Cerner
MTX
 
Referred To:  

Questions? Comments? Contact Laura Gopaul