Methotrexat-Nachweis im menschlichen Serum – Vergleich zwischen einer enzymatischen und einer enzymimmunologischen Methode

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Abstract
High-dose methotrexate [an antineoplastic drug] therapy [in humans] with following citrovorum factor rescue necessitates the regular determinations of methotrexate (MTX) serum concentrations. A simple enzymatic assay by MTX-induced inhibition of dihydrofolate reductase is described. The results gained with this assay are compared with those of a new enzyme immunoassay (MTX-EMIT). Between 5 .times. 10-7 M and 1 .times. 10-3 M the results of both tests are nearly the same, and the coefficient of correlation is 0.9980. At MTX concentrations below 5 .times. 10-7 M the results of the MTX-EMIT lie nearly always higher than and differ considerably from those of the enzymatic method; r is only 0.7007. If it is possible to enhance the sensitivity of the MTX-EMIT, this test enables the very quick and easy determination of MTX serum concentrations in the whole range of clinical importance.