DPYD is the gene that provides the instructions for making the DPD enzyme dihydropyrimidine dehydrogenase.

This is an important enzyme because it helps the body metabolise certain substances, including fluoropyrimidine-based chemotherapies, such as 5-fluorouracil (5-FU), which are used to treat a variety of cancers.

Most people have two working copies of the DPYD gene, one inherited from their mother and the other from their father. When the DPYD gene does not work properly due to certain changes (variations) in the gene, the body may not produce enough DPD enzyme, resulting in DPD deficiency.
People with DPD deficiency may not have enough DPD enzyme to breakdown some chemotherapies safely. This can lead to a build-up of drug in the body during treatment, which may result in toxic side effects, which sometimes can be life threatening.

The test will help Healthcare Practitioners to decide on the best and safest course of treatment for patients. If variation is identified in the DPYD gene, Health Practitioners may adjust the dosage of patients chemotherapy of choose an alternative treatment if necessary.