CLCA1 and colorectal carcinoma: We next analyzed the CLCA1 serum expression level in 100 CRC patients and 76 healthy controls by ELISA and found that the CLCA1 serum expression level was significantly lower in CRC patients than in healthy controls (1.48 ± 1.06 ng/mL vs 1.06 ± 0.73 ng/mL, P = 0.0018, t-test, Fig. 2a).