Specimen:

Plasma or CSF

Collection Medium:

Alternate
Collection Media:

Call laboratory for additional acceptable specimen collection 
containers.

Minimum:

2 ml whole blood in light green lithium heparin tube or one light green 
microtube or CSF.

Testing
Schedule:

0700-1630 Monday through Friday.
0600-1400 Saturday, Sunday and holidays.
Sample must be received by 1400 for same day service.

Analytic Time:

3 hours (upon receipt in laboratory)

Reference Range:

Clinical toxicity more frequent with serum concentrations:
>10 Exp-5 molar at 24 hrs. post infusion
>10 Exp-6 molar at 48 hrs. post infusion
>10 Exp-7 molar at 72 hrs. post infusion

Test
Limitations:

Specimens from patients who have received preparations of mouse 
monoclonal antibodies for diagnosis or therapy may contain human 
anti-mouse antibodies (HAMA).  HAMA present in serum may interfere in 
immunoassays which utilize mouse monoclonal antibodies.  These 
specimens should not be assayed with the TDx/TDxFLx Methotrexate II 
assay.

Methodology:

FPIA (Fluorescent Polarization ImmunoAssay)

Sample
Processing:

Centrifuge at 3000 RPM for 10 minutes.
Label transport tube with two patient identifiers, date and time of 
collection.

Sample
Storage:

Freeze specimen immediately.
Protect specimen from light.

Transport
Instructions:

Place requisition into outside pocket of bag.
Place specimen into zip-lock type bag, seal bag.
Place dry ice on top of specimen in styrofoam container.
Dry Ice up to 24 hours.

CPT Code:

83520

See Additional Information:
Chemistry Critical Lab Values