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 Test Performed

Daily

Analytic Time

2 hours

Soft Order Code

MTX24

MiChart Code

Methotrexate, 24 Hour

Laboratory

Chemical Pathology

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Specimen Requirements

Offsite 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.

Container

Yellow Top Tube

Normal Volume

0.5 mL serum, plasma, or CSF

Minimum Volume

0.25 mL serum, plasma, or CSF

Billing Information

Fee Codes


CPT Code

80299

LOINC

3793-7

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