title: Enzymatic assay for methotrexate in serum and cerebrospinal fluid.
abstract: We describe an assay for methotrexate in biological fluids. The assay is based on inhibition by methotrexate of dihydrofolate reductase from Lactobacillus casei. The lower limit of sensitivity in serum is 2 X 10(-8) mol (about 10 mug) of methotrexate per liter. Within-run precision is +/- 5% (coefficient of variation) and day-to-day variation is 18%. Advantages of the assay are ease of manipulation, high sensitivity, and specificity.
mesh_terms: D005069:Evaluation Studies as Topic; D006801:Humans; D007780:Lacticaseibacillus casei / Q000201:enzymology; D008727:Methotrexate / Q000032:analysis* / Q000097:blood / Q000134:cerebrospinal fluid; D011786:Quality Control; D013762:Tetrahydrofolate Dehydrogenase; D013997:Time Factors
chemical_list: D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate