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Test Code DPYDG Dihydropyrimidine Dehydrogenase, DPYD Full Gene Sequencing, Varies

Secondary ID


Useful For

Identifying individuals at increased risk of toxicity when considering 5-fluorouracil (5-FU) and capecitabine chemotherapy treatment


For an individual with suspected dihydropyrimidine dehydrogenase (DPD) deficiency, this test may be useful in identifying variants associated with decreased or absent DPD enzyme activity

Method Name

Polymerase Chain Reaction (PCR) Followed by DNA Sequence Analysis

Reporting Name

DPYD Full Gene Sequencing

Specimen Type


Advisory Information


Specimen Required

Multiple whole blood EDTA genotype tests can be performed on a single specimen after a single extraction. See Multiple Whole Blood EDTA Genotype Tests in Special Instructions for a list of tests that can be ordered together.


Submit only 1 of the following specimens:


Specimen Type: Whole blood

Container/Tube: Lavender top (EDTA)

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred)/Refrigerated


Supplies: DNA Saliva Collection Kit (T651)

Specimen Type: Saliva

Container/Tube: Oragene DNA Self-Collection Kit (T651: fees apply)

Specimen Volume: Full tube

Collection Instructions:

1. Fill tube to line.

2. Send specimen in original container per kit instructions.

Specimen Stability Information: Ambient


Specimen Type: DNA

Container/Tube: 2 mL screw top tube

Specimen Volume: 100 mcL (microliters)

Collection Instructions:

1. The preferred volume is 100 mcL at a concentration of 250 ng/mcL.

2. Include concentration and volume on tube.

Specimen Stability Information: Frozen (preferred)/Ambient/Refrigerated

Specimen Minimum Volume

Blood: 0.45 mL
Saliva: Full tube of saliva

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

5-Fluorouracil (5-FU) and its orally administered prodrug, capecitabine, are fluoropyrimidine-based chemotherapeutic agents that are widely used for the treatment of colorectal cancer and other solid tumors.


The dihydropyrimidine dehydrogenase (DPYD) gene encodes the rate-limiting enzyme for fluoropyrimidine catabolism and eliminates over 80% of administered 5-FU. Dihydropyrimidine dehydrogenase (DPYD) activity is subject to wide variability, mainly due to genetic variation (table 1). This results in a broad range of enzymatic deficiency from partial (3%-5% of population) to complete loss (0.2% of population) of enzyme activity.(2,3) Patients who are deficient in DPYD are at an increased risk for side effects and toxicity when undergoing 5-FU treatment.(4) In addition, pathogenic homozygous or compound heterozygous variants within DPYD are associated with dihydropyrimidine dehydrogenase (DPD) deficiency. DPD deficiency shows large phenotypic variability, ranging from no symptoms to a convulsive disorder with motor and mental retardation.


Table 1. Known Genetic Variations Associated with Fluoropyrimidine Treatment


cDNA numbering

Alternative Name

Enzyme Activity



No variations identified






No activity or significantly reduced activity

High risk for fluoropyrimidine toxicity











Reduced activity

Increased risk for fluoropyrimidine toxicity





Probable reduced function

Increased risk for fluoropyrimidine toxicity









Normal activity**

Normal risk for fluoropyrimidine toxicity







*Other or novel variations, besides those listed here, may also impact fluoropyrimidine-related side effects and tumor response and will be reported if detected.

**Alleles that are categorized as having normal enzyme activity (eg, *4, *5, *6, *9A) will not be reported if detected because variants with normal enzyme activity are not expected to impact fluoropyrimidine-related side effects and tumor response.


The DPYD gene is located on chromosome 1 and contains 2 transcripts. The longer transcript (NM_000110.3) contains 23 exons, and the shorter transcript (NM_001160301.1) contains 6 exons, with exon 6 being unique to this transcript. All exons from the longer transcript (NM_000110.3) and exon-intron boundaries are assessed.


Genetic variations involved in the metabolic pathway of fluoropyrimidines have been shown to contribute to the differences in clinical outcomes including toxicity and tumor response.

Reference Values

An interpretive report will be provided.


Evaluation and categorization of variants is performed using the most recent published American College of Medical Genetics and Genomics recommendations as a guideline.(5) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.


For additional information regarding pharmacogenomic genes and their associated drugs, see the Pharmacogenomic Associations Tables in Special Instructions. This resource also includes information regarding enzyme inhibitors and inducers, as well as potential alternate drug choices.

Clinical Reference

1. Online Mendelian Inheritance in Man: Dihydropyrimidine dehydrogenase deficiency. #274270. Updated 4/18/2012. Available from

2. Caudle KE, Thorn CF, Klein TE, et al: Clinical Pharmacogenetics Implementation Consortium guidelines for dihydropyrimidine dehydrogenase genotype and fluoropyrimidine dosing. Clin Pharmacol Ther 2013;94(6):640-645

3. Morel A, Boisdron-Celle M, Fey L, et al: Clinical relevance of different dihyropyrimidine dehydrogenase gene single nucleotide polymorphisms on 5-fluorouracil tolerance. Mol Cancer Ther 2006 Nov;5(11):2895-2904

4. FDA Table of Pharmacogenomic Biomarkers in Drug Labeling. Available at:

5. Richards S, Aziz N, Bale S, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med 2015;17(5):405-424

6. Offer SM, Fossum CC, Wegner NJ, et al: Comparative functional analysis of DPYD variants of potential clinical relevance to dihydropyrimidine dehydrogenase activity. Cancer Res 2014;74(9):2545-2554

Day(s) and Time(s) Performed

Varies; 8 a.m.

Analytic Time

5 days (Not reported on Saturday or Sunday)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
DPYDG DPYD Full Gene Sequencing 94198-9


Result ID Test Result Name Result LOINC Value
48263 DPYD Predicted Toxicity Risk 83009-1
48264 Result Details 82939-0
48268 Interpretation 69047-9
48266 Method 49549-9
48269 Disclaimer 62364-5
48270 Reviewed by 18771-6
92011 Additional Information 48767-8


1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing (Spanish) (T826)

2. If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Pharmacogenomics Test Request (T797)

-Therapeutics Test Request (T831)