The grade 3/4 events of anti-EGFR MoAbs were noted in 304 of 4543 patients, yielding the incidence of 6.7 % (95 % CI 5.2–8.7 %), whereas in the control group, the incidence was 3.7 % (95 % CI 2.5–5.4 %) (Online Resource Table 2), implying that addition of anti-EGFR MoAbs increased the risk of hypokalemia (RR = 1.68, 95 % CI 1.40–2.03; p < 0.001) (Fig. 2). This evidence concerns the gene EGFR and Hypokalemia.