Specimen Type/Requirements

Red top (Serum w/out gel) tube - Serum

Do not collect in gel separator tubes.

Patients who have received glucarpidase (carboxypeptidase G2) as a high dose methotrexate rescue therapy should not be tested with this method.  These patients have an increased level of metabolite that cross reacts with the methotrexate antibody.  These metabolites stay in circulation for 5-7 days.

Test is not affected by hemolysis or lipemia.