Test Overview
Test Methodology

FPIA

Test Usage

Monitor therapeutic drug level, evaluate potential toxicity

Reference Range *

No precise relationship between methotrexate serum levels and antineoplastic efficacy has been established. Following a 4-6 hour intravenous methotrexate infusion with dosages ranging from 50 mg/m2 - 15 g/m2, a patient with a 24 hr serum level > 5 - 10 umol/L, a 48 hr serum level > 0.5 - 1.0 umol/L, and a 72 hr serum level > 0.2 umol/L is at an increased risk of toxicity if conventional low dose leucovorin rescue is given. In this case, high dose leucovorin rescue would be indicated.

* 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
MTX4
MiChart Code
Methotrexate, 4 Hour
Laboratory
Chemical Pathology
Section
Drug Analysis
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