The diagnostic value of serum gastrokine 1 (GKN1) protein in gastric cancer

Early detection of cancer provides effective treatment and saves lives. The objective of this study was to determine whether serum gastrokine 1 (GKN1) protein is a gastric cancer‐specific diagnostic biomarker. The serum concentration of GKN1 in healthy individuals (median: 6.34 ng/μL, interquartile range (IQR): 5.66‐7.54 ng/μL) was significantly higher compared with the levels in gastric cancer patients (median: 3.48 ng/μL, IQR: 2.90‐4.11 ng/μL; P < .0001). At the optimum cutoff (4.94 ng/μL) of serum GKN1 protein, the sensitivity and specificity were 91.2% and 96.0%, respectively, for gastric cancer. Using serum GKN1 protein as the diagnostic reference, the ROC curve showed a satisfactory diagnostic efficacy with an AUC value of 0.9954 (95% CI 0.9919‐0.9988) and Youden index of 0.8740. In addition, the diagnostic accuracy of the serum GKN1 protein at the optimum cutoff was 0.9675. Interestingly, serum GKN1 concentrations in patients with advanced gastric cancer (AGC; median: 3.11 ng/μL, IQR: 2.72‐3.72 ng/μL) were lower than in patients with early gastric cancer (EGC; median: 4.31 ng/μL, IQR: 3.88‐4.88 ng/μL). The diagnostic accuracies at the optimum serum GKN1 cutoff were 0.8912 and 0.9589 for EGC and AGC, respectively. Furthermore, the serum GKN1 concentrations robustly discriminated the patients with gastric cancer from the patients with colorectal, liver, lung, breast, pancreatic, ovary, and prostatic cancers with AUC values greater than 0.94. These data suggest that serum GKN1 is a promising and highly specific diagnostic biomarker for the prompt detection of early and advanced gastric cancers.