Patient with cancer about to undergo fluoropyrimidine treatment.
The goal of this test is to adjust fluoropyrimidine treatment in individuals with one or more variants, depending on the genotype of the DPYD gene. It consists in genotyping 4 recurrent DPYD variants associated with an increased risk of severe fluoropyrimidine toxicity, including 2 variants (c.1905+1G>A/DPYD*2A and c.1679T>G) with no dihydropyrimidine dehydrogenase (DPD) function (activity value = 0), and 2 variants (c.2846A>T and c.1236G>A, HapB3 proxy) with decreased DPD function (activity value = 0.5). For the HapB3 haplotype it is important to note that this test detects only the c.1236G>A variant and not the intronic variant c.1129-5923C>G.
The 4 variants are genotyped by a TaqMan assay in duplicate (2 independent DNA extractions) from 4 independent PCR reactions (one for each variant).
Fluoropyrimidine metabolism, efficacy and risk of toxicity may be influenced by genetic and non-genetic factors that are not assessed by this test. Its clinical validity is limited and known to vary significantly depending on ethnicity. This test detects the 4 most frequent DPYD drug response variants in individuals of European descent and does not detect some of the most frequent variants in other ethnic groups, especially Africans and East Asians. Over 100 variants altering DPD activity have been described to date and other functional variants remain to be discovered. This test will therefore not detect all possible clinically relevant DPYD variants. A negative result does not rule out the possibility that the individual harbors a drug response variant not included in the assay, especially if of non-European descent. DNA variants located in primer binding sites and rare genotyping errors can result in inaccurate diagnosis.
Turnaround time: 3-5 working days
Specimen accepted:
- 2 x 4 mL blood in EDTA tubes (purple top tube)
- DNA: min 10 ug
- For any other sample type, contact the laboratory for testing availability
Please review the Preparation and Shipping Instructions for additional details.
Submit your test request using our molecular genetics requisition.