There are 6/69 (8.7%) patients who developed leukopenia and harbored NUDT15 variant, thus showing a strong association for thiopurine-induced toxicity.
NUDT15R139C was strongly associated with the incidence of leukopenia (70.2% mutation vs. 12.8% wild type; P=8.61×10<sup>-19</sup> ; odds ratio, 10.80; 95% CI, 5.89-19.83).