Genotyping should be considered the primary choice for pre-treatment evaluation of thiopurine methyltransferase function.
BACKGROUND AND AIMS: A pre-treatment determination of the thiopurine S-methyltransferase (TPMT) genotype or phenotype can identify patients at risk of developing severe adverse reactions from thiopurine treatment. The risk of misclassifying a patient might be dependent on the method used. The aim of this study was to investigate the concordance between TPMT genotyping and phenotyping. METHODS: T