These tests exist, however, we are not aware of any CLIA-approved commercial lab offering DPD phenotype testing in the USA.
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.
This depends on several factors including the test ordered. Generally testing takes 5-10 days, though some labs may take up to 3 weeks.
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.
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.
In Europe they do, in the USA the NCCN has stated they are concerned that reducing fluoropyrimidine dosing may reduce treatment effectiveness.
Our best estimate is ~7% but this will depend on the genotyping test ordered
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.
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.
