When do you consider testing for dihydropyrimidine dehydrogenase (DPD) for patients prior to treatment with 5-FU/capecitabine?

Happy to address this question! It is my practice to test for DPD deficiency in all patients who will receive a first treatment with a fluoropyrimidine agent (5-FU or capecitabine). My objective in doing this is to avoid infrequent but readily avoidable severe toxicities and deaths related to DPD de...