Frequently Asked Questions

Frequently Asked Questions

Frequently Asked Questions2022-11-01T19:36:50-04:00
I have heard that there are other DPD/DPYD tests besides genetics that may be more accurate, should I order that instead?2022-11-01T18:14:50-04:00

These tests exist, however, we are not aware of any CLIA-approved commercial lab offering DPD phenotype testing in the USA.

Do you recommend any specific DPYD test?2022-11-01T18:14:29-04:00

AUDT does not recommend any specific test, however, we recommend using a CLIA-approved test that includes several of the most common alleles including DPYD*2A, DPYD*13, DPYD p.D949V, and DPYD HapB3. A list of these tests can be found at the NCBI Genetic Testing Registry.

How long does it take to get the results?2022-11-01T18:13:41-04:00

This depends on several factors including the test ordered. Generally testing takes 5-10 days, though some labs may take up to 3 weeks.

How much does DPYD testing cost?2022-11-01T18:13:21-04:00

This depends on several factors including the test ordered and insurance coverage. In general, testing costs $150-$500. Some insurance covers testing, in which case the patient may not have any payment. It may not be possible to determine whether there will be any cost to the patient prior to ordering.

Is there evidence that reducing fluoropyrimidine dosing in DPYD carriers reduces treatment effectiveness?2022-11-01T18:13:03-04:00

No, there is no evidence of reduced efficacy. There is some evidence that efficacy is the same but this has not been confirmed. It is confirmed that reducing doses results in similar drug concentrations and toxicity risk, so it is reasonable to assume that efficacy is also similar.

Why don’t clinical guidelines committees recommend DPYD testing?2022-11-01T18:07:34-04:00

In Europe they do, in the USA the NCCN has stated they are concerned that reducing fluoropyrimidine dosing may reduce treatment effectiveness.

How common is carrying a diminished activity DPYD variant?2022-11-01T18:07:13-04:00

Our best estimate is ~7% but this will depend on the genotyping test ordered

Why don’t doctors order DPYD genotyping for all patients?2022-11-01T18:06:45-04:00

There are lots of possible reasons, but the most commonly cited reasons are the perceived low frequency of DPYD variants and the lack of recommendations from clinical guidelines committees.

What is the risk of toxicity in DPYD variant carriers who receive standard fluoropyrimidine doses?2022-11-01T18:05:27-04:00

The risk of toxicity depends on many factors, but generally is >50%, with ~30% risk of hospitalization and ~3% risk of death. Of note, DPYD carriers are not guaranteed to experience toxicity and non-carriers are not guaranteed to avoid toxicity.

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