Subcutaneous administration, higher age and lower renal function are associated with erythrocyte methotrexate accumulation in Crohn’s disease: a cross-sectional study oleh M. M. van de Meeberg, M. L. Seinen, H. H. Fidder, M. Lin, B. Oldenburg, N. K. de Boer, G. Bouma, R. de Jonge, M. Bulatović Ćalasan, the Dutch Initiative on Crohn and Colitis (ICC)