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Clinical calculator summary

DPYD Activity Score Calculator

DPYD activity score summarizes predicted DPD enzyme activity and fluoropyrimidine toxicity risk.

Evidence-based context for fast calculator use

Purpose:
Support pretreatment 5-FU/capecitabine pharmacogenomic dose discussion
Population:
Patients being considered for systemic fluoropyrimidine therapy with a reported DPYD genotype/activity score
Factors:
DPYD activity score, Drug/regimen context, Laboratory-reported phenotype
Reference:
CPIC fluoropyrimidine-DPYD guideline update; DPWG DPYD fluoropyrimidine guideline
HomeDPYD / DPD Fluoropyrimidine Activity Score
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DPYD / DPD Fluoropyrimidine Activity Score

Clinical Context & Background

DPYD encodes dihydropyrimidine dehydrogenase (DPD), the main enzyme responsible for fluoropyrimidine catabolism. Reduced DPD activity increases the risk of severe or fatal toxicity from 5-fluorouracil and capecitabine.
This calculator uses the DPYD activity score reported by a validated pharmacogenomic assay or clinical laboratory. Commonly tested variants include DPYD*2A / c.1905+1G>A, DPYD*13 / c.1679T>G, c.2846A>T, and c.1129-5923C>G / c.1236G>A (HapB3), but laboratories may include additional alleles and phenotype rules. Use the report phenotype when available.
Guidance is summarized from CPIC/DPWG-style recommendations and should be reconciled with the current local guideline, drug label, regimen intent, organ function, and clinician/pharmacist judgment.
Formula Logic
DPYD activity score is the sum of the activity values assigned to both DPYD alleles. Reported scores commonly range from 0 to 2.

Reference Data

Activity ScorePredicted PhenotypeStarting-Dose Guidance
2Normal metabolizerStandard starting dose; routine monitoring
1 or 1.5Intermediate metabolizerReduced starting dose, commonly 50%, then titrate
0 or 0.5Poor metabolizerAvoid fluoropyrimidines when possible; specialist input if unavoidable

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Frequently Asked Questions

Can this calculator replace a DPYD laboratory report?

No. It requires a validated DPYD genotype or activity score from a clinical laboratory. Use the laboratory phenotype and local pharmacogenomics guidance when they differ.

Does a normal DPYD activity score eliminate fluoropyrimidine toxicity risk?

No. A normal score lowers concern for known DPYD-mediated risk but does not eliminate toxicity risk from other genetic, renal, hepatic, drug-interaction, regimen, or patient-specific factors.

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