Changes in liver histology during methotrexate therapy of psoriasis correlated to the concentration of methotrexate and folate in erythrocytes.

To investigate, whether an assessment of the folate and methotrexate concentrations in erythrocytes could be used to indicate incipient histological liver changes, these 2 parameters were related to liver histology in series of liver biopsies (means 4.3 biopsies) from 31 long-term methotrexate-treated psoriasis patients. Logistic regression analysis showed that the probability of changes in liver histology during methotrexate therapy increased significantly with increasing erythrocyte methotrexate concentrations and with decreasing erythrocyte folate concentration. The application of these variables as a decisive criterion when to institute liver biopsy surveillance needs further studies, but can probably help reduce the number of liver biopsies to be taken during long-term methotrexate therapy considerably.