TABLE 5.

Pros and cons of using different DPD testing methods

DPYD genotype	DPD phenotype (uracil concentration)
A simple and well‐known technique. Simple for the clinicians to translate. Validated in larger prospective clinical trials. Commercialized assay available.	Cheap. Continuous variable. Changes over time. May deflect current DPD activity better Can detect patients with rare DPYD variants
Only examines known DPYD variants Variation of clinically relevant DPYD variants varies across the world DPD activity of patients that is compound heterozygous cannot be decided.	Blood samples are unstable. Risk of pre‐analytical errors Lack of prospective data Affected by kidney function The uracil concentration is affected by food intake and the circadian rhythm. Lack of standardization of methods