Test Overview
Test Methodology

Enzyme Homogeneous Competitive Immunoassay

Test Usage

Monitor therapeutic drug level, evaluate potential toxicity

Reference Range *

A therapeutic range for Methotrexate has not been defined. No precise relationship between methotrexate serum levels and antineoplastic efficacy has been established. Serum concentrations are monitored during high-dose therapy to identify the time when active intervention by leucovorin rescue should be initiated. Serum concentrations indicative of an increased risk of toxicity after a 4-6 hour high-dose infusion are as follows:
24 hr >5.00 umol/L
48 hr >0.50 umol/L
72 hr >0.10 umol/L

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Details
Days Set Up
Daily
Analytic Time

2 hours

Soft Order Code
MTX
MiChart Code
Methotrexate Level
Laboratory
Chemical Pathology
Section
Automation
Specimen Requirements
Collection Instructions

Collect blood in a red top or green top tube; do not use SST tube. Centrifuge, aliquot serum into a plastic vial, and refrigerate. Cerebrospinal fluid is also an acceptable specimen.

Rejection Criteria
SST tube not acceptable.
Yellow Top Tube
Red Top Tube
Normal Volume
0.5 mL serum, plasma, or CSF
Minimum Volume
0.25 mL serum, plasma, or CSF
Billing
CPT Code
80299
Fee Code
23327
LOINC
3793-7
Resources