Red Cell Methotrexate Polyglutamates

MTX is a folate analogue drug used in low dose for the treatment of rheumatoid arthritis, severe psoriasis, and inflammatory bowel disease (IBD). The effects of MTX are depletion of reduced folates through inhibition of dihydrofolate reductase (DHFR). Once MTX enters the cell, it is polyglutamated with up to seven glutamate residues through the action of folylpolyglutamyl synthetase (FPGS). Polyglutamates 2-7 are stored intracellularly inhibiting different enzymes. Monitoring Methotrexate polyglutames in red blood cells is useful for confirming adherence to therapy.

Clinical details: 
For psoriasis and IBD patients, monitoring MTX and PLG2-5 levels is useful for confirming adherence to methotrexate therapy. For RA, recent studies have suggested that there is a correlation between levels of MTXGlu 3-5 and disease activity. Patients with total MTXGlu3-5 levels <60nM are more likely to have poor clinical response.
Synonyms or keywords: 
nmols/L RBC
Sample type and Volume required: 
EDTA whole blood
Turnaround time: 
3 weeks
Storage and transport: 
Keep sample at room temperature. Do not freeze.
Purine Research Laboratory at St Thomas'
020 7188 1266
St Thomas’ Hospital
North Wing - 4th Floor
Westminster Bridge Road
London SE1 7EH
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 12/04/2016