A study by Etienne et al has raised questions regarding the utility of DPD activity alone to predict patients at risk for fluoropyrimidine toxicity. They prospectively studied 185 patients treated with 5FU containing chemotherapy regimens. They found a normal distribution of DPD activity with a mean value of 0.222 nmol/min/mg protein. They did not find any correlation between DPD activity and 5FU toxicity.