This result signifies that the patient has an allele combination with uncertain and/or unknown function alleles. The expected phenotype for this patient cannot be determined currently based on the TPMT diplotype result. Consider evaluating TPMT erythrocyte activity to assess TPMT phenotype. Erythrocyte TPMT activity test results can be falsely low at diagnosis of leukemia and is unreliable in the case of recent red blood cell transfusions. If thiopurines are required and TPMT status is unknown, monitor closely for toxicity. Please consult a clinical pharmacist for more specific information about how TPMT function influences drug dosing.