Inactivated/Replace Test
Effective Date
07/21/2025
Included in Report
Replacement Test
Inactivated/Replace Test
Inactivated Test Details
Mnemonic
MTXS
Ordering Code
3620520
CPT-4 Codes(s)
80204
Replacement Test Details
Mnemonic
METRX
Ordering Code
3401077
CPT-4 Codes(s)
80204
Turnaround Time
2 - 3 days
Performed
Monday - Saturday
Legacy Code
METRX
Example Report
Specimen Information
Patient Preparation
Collect 24, 48, or 72 hours after dose. Record hours from last dose on specimen container.
Collect
Red top
Specimen Preparation
Centrifuge, separate serum from cells and send 1.0 mL serum in an amber screw capped plastic vial. Protect sample from light.
Alternate Specimen
Plasma: Lavender (EDTA), green sodium or lithium heparin, gray fluoride oxalate - protected from
light
light
Minimum Volume
0.2 mL
Transport Temperature
Frozen
Rejection Criteria
Serum separator tube (SST) or any other tube with additives, thawed samples
Stability
Room temperature: 24 hours
Refrigerated: Unacceptable
Frozen: 5 days
Refrigerated: Unacceptable
Frozen: 5 days
Methodology
Immunoassay (IA)
Reference Range
<5.00 umol/L at 24 hours
<0.50 umol/L at 48 hours
<0.20 umol/L at 72 hours
For conventional low dose leucovorin rescue.
<0.50 umol/L at 48 hours
<0.20 umol/L at 72 hours
For conventional low dose leucovorin rescue.
Performing Laboratory
Quest
New York DOH Approval Status
Yes