Individually, NUDT15 c.415C > T had a sensitivity and specificity of 57.9% and 94.0% (odds ratio [OR] = 21.45, 95% CI 5.94–77.41, p < 0.001), respectively, for predicting thiopurine-induced leukopenia, while NUDT15 c.52G > A was only observed in patients with leukopenia. The gene discussed is NUDT15; the disease is Decreased total leukocyte count.