Methotrexate Test Dose Use and Frequency of Laboratory Abnormalities in Patients Initiating Treatment

Area of Science:

• Pharmacology
• Clinical Medicine
• Dermatology and Rheumatology

Background:

• Dermatology guidelines suggest methotrexate test doses may not be needed for low-risk patients.
• Few studies have evaluated the utility of test doses for detecting or preventing methotrexate toxicity.
• Rheumatology guidelines do not mention methotrexate test doses.

Purpose of the Study:

• To determine the frequency of laboratory abnormalities in patients starting low-dose, oral methotrexate.
• To compare outcomes between patients who received a methotrexate test dose and those who did not.

Main Methods:

• Retrospective cohort analysis of 2,575 adult patients initiating methotrexate.
• Defined test dose as ≤15 mg with labs within 3-10 days.
• Compared Grade 2+ laboratory abnormalities over 4 months between test dose and non-test dose groups.

Main Results:

• No significant difference in Grade 2+ laboratory abnormalities between groups (6.82% test dose vs. 4.34% non-test dose, P=0.09).
• In the test dose group, 2.73% experienced Grade 2+ abnormalities within 3-10 days.
• Rheumatology patients comprised over 91% of the study population.

Conclusions:

• Methotrexate test doses appear to have limited value in detecting or preventing significant laboratory abnormalities.
• Findings support evolving dermatology guidelines on methotrexate test dose use.
• The routine use of a test dose for initiating methotrexate may not be necessary.