KRT18 and breast cancer: As for the testing methods (Figure 3C), four studies enrolled 2575 patients used ELISA to detect CK18 expression, which predicted a worse outcome of breast cancer patients (HR = 1.21, 95%CI: 1.08–1.35, P=0.0001) than studies used IHC (HR = 0.83, 95%CI: 0.71–0.96, P<0.0001).