• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer

Johns Hopkins Arthritis Center

Show Search
Hide Search
  • Disease Information
    • Rheumatoid Arthritis
    • Psoriatic Arthritis
    • Ankylosing Spondylitis
    • Osteoarthritis
    • Gout
    • Osteoporosis
  • Patient Corner
    • Drug Information Sheets
    • Managing Your Arthritis
    • RheumTV – Patient Education Video Library
  • Our Research
    • Patient-Centered Outcomes Research
    • Current Research Studies
    • The Camille Julia Morgan Arthritis Research and Education Fund
  • About Us
    • Appointment Information
    • Contact Us
    • Our Faculty
    • Our Staff
    • Rheumatology Specialty Centers
  • Donate
Home / Arthritis News / Can Measuring Polyglutamated Methotrexate in Red Blood Cells Help Guide Dosing

Can Measuring Polyglutamated Methotrexate in Red Blood Cells Help Guide Dosing

February 17, 2010 By Arthritis Center

Methotrexate
Methotrexate

Measuring the amount of polyglutamated methotrexate within red blood cells has been proposed as an objective method of tracking medication response and predicting drug toxicity.  However, there are only limited data evaluating this method.  Here, Stamp et al (Arthritis Rheum 2010; 62(2)): 359) cross-sectionally explore the associations of RBC polyglutamated methotrexate levels with disease activity and adverse events.

Methods

Patients with rheumatoid arthritis receiving treatment with methotrexate for at least 3 months and followed in Christchurch, New Zealand had trough concentrations of the number of glutamate moieties associated with RBC methotrexate (1 to 5 glutamates) measured.  The association of the extent of RBC polyglutamated methotrexate with disease activity and safety measures were explored.

Results

A total of 192 patients were studied.  The average age of enrolled patients was 60 years with average disease duration of approximately a decade.  About 90% of the patients were on methotrexate monotherapy for a median of three years prior to enrollment at a current median dose of 15 mg/week.

Methotrexate dosage was associated with higher polyglutamate concentrations and was also correlated with several indicators of disease activity.  Polyglutamated RBC methotrexate was correlated with disease activity measures (swollen and tender joint counts and the DAS28 score) and other disease status measures (fatigue and HAQ score), even after adjusting for demographic and lifestyle factors, concomitant treatments, and autoantibodies.  However, there was no association with disease activity after adjusting for estimated glomerular filtration rate and methotrexate dosage, except to pentaglutamated RBC methotrexate, which was significantly higher in patients categorized as high disease activity (DAS28>3.2) compared to those with lower disease activity.  These results were not substantially altered after accounting for RBC folate concentration.  There were no associations between polyglutamated RBC methotrexate concentrations and adverse events.

Conclusions

Higher polyglutamated RBC methotrexate concentration was not an indicator of disease control or of adverse events in this cross-sectional analysis.

Editorial Comment

Methotrexate is a slow acting medication that may not lead to an acceptable clinical response in all patients.  Thus, there is some value in having an objective advanced predictor of response, so that valuable time is not wasted titrating an ultimately ineffective medication.  While this study is compelling, larger than other prior studies, and considers additional confounding factors that were neglected in the other studies, it is still unclear for the findings presented here whether there is a clinical role for measuring polyglutamated RBC methotrexate.  The major liability to the study presented here is the cross-sectional nature of the analysis, which limits any ability to assess temporality.  In particular, using these cross-sectional data to make conclusions about the ability of polyglutamated RBC methotrexate to predict adverse events is prone to misinterpretation.  Further work will require longitudinal studies in methotrexate naïve patients in order to be interpretable.

Receive the Latest News from Johns Hopkins Rheumatology

Receive the Latest News from Johns Hopkins Rheumatology

Join our mailing list to receive the latest news and updates from Johns Hopkins Rheumatology.

Interested In

You have Successfully Subscribed!

Arthritis Center

Founded in 1998, the Arthritis Center at Johns Hopkins is dedicated to providing quality education to patients and healthcare providers alike.

Use of this Site

All information contained within the Johns Hopkins Arthritis Center website is intended for educational purposes only. Physicians and other health care professionals are encouraged to consult other sources and confirm the information contained within this site. Consumers should never disregard medical advice or delay in seeking it because of something they may have read on this website.

Primary Sidebar

Recent News

Exercise Tips for Arthritis Patients

How Does Exercise Affect my Joints? How Frequently Should I Be Exercising? Should I Lose Weight for Exercise to be

Risks and Benefits of Biologic Medications

Victoria Ruffing, RN, BC, Director of Patient Education at the Johns Hopkins Arthritis Center, shares the risks and benefits of biologic for

How to Manage Rheumatoid Arthritis Flares

Through research, doctors have a clearer understanding of how flares can impact a patient on a personal and emotional level. Dr. Uzma Haque

Complementary & Alternative Medicines for Psoriatic Arthritis

There are many complementary & alternative medicines and practices that have been found to be beneficial in curbing arthritis pain,

I can’t be a runner because I have Rheumatoid Arthritis (RA), right?

Dr. Manno discusses running and Rheumatoid Arthritis. Is it an option for the RA patient?

News Categories

  • Ankylosing Spondylitis News
  • Fibromyalgia News
  • Gout News
  • Lupus News
  • Osteoarthritis News
  • Osteoporosis News
  • Psoriatic Arthritis News
  • Rheumatoid Arthritis News
RheumTV Logo

Rheum.TV is an informational platform created to educate patients living with a rheumatic disease. With over 100 disease education videos produced by the team at Johns Hopkins Rheumatology.

Visit Rheum.TV

Footer

Johns Hopkins Rheumatology

  • Johns Hopkins Rheumatology
  • Johns Hopkins Lupus Center
  • Johns Hopkins Lyme Disease Research Center
  • Johns Hopkins Myositis Center
  • Johns Hopkins Scleroderma Center
  • Johns Hopkins Sjögren’s Syndrome Center
  • Johns Hopkins Vasculitis Center

Connect With Us

  • Facebook
  • Twitter
  • YouTube

Johns Hopkins Medicine

© 2023 Johns Hopkins Arthritis Center
Patient Privacy