The Test Sample
What is being tested?
Methotrexate is a drug that has been in use since the 1960s to treat childhood acute lymphocytic leukemia, lymphoma, and cancers of the lung, head, neck, and breast. This test measures the amount of methotrexate in the blood.
Methotrexate prevents cells from using folate to make DNA and RNA, slowing growth of new cancer cells. Because it can also deter growth of new skin cells, methotrexate is also used to treat psoriasis. The drug blocks several enzymes involved in the immune system and can minimize joint damage associated with rheumatoid arthritis (RA).
Methotrexate must be carefully monitored. Even when used correctly, it can cause significant side effects. Increased concentrations can be toxic, potentially damaging the liver, kidneys, and lungs and suppressing cell production in the bone marrow.
Methotrexate dosing depends upon the condition being treated. Methotrexate levels in the blood typically rise after a dose and then fall gradually. Methotrexate is eliminated from the body by the kidneys, so any condition that decreases kidney function or interferes with drug clearance has the potential to increase blood concentrations.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed, but timing of the sample for testing is important and a health practitioner may specify collection at a certain number of hours after a methotrexate dose.