Usually, symptoms of gastric cancer are absent or nonspecific in the early stages of gastric cancer, and they are easily ignored . A prospective study in China involving 102,665 subjects found that 48% of patients with gastrointestinal malignancy had no indicatory features, and the detection rate of gastrointestinal tumors among those patients was 2.5% . Thus, such indicatory features alone cannot predict gastrointestinal tumors, and regular endoscopic screening of high-risk patients is key for early diagnosis of gastric cancer. However, the adaptability of the existing risk prediction rules to Chinese health examination populations is not yet clear. Therefore, in this study, we compared the efficacy of three prediction rules: the ABC method, the Scoring System from JPHC, and Li’s Scoring System.
In our analysis, the comparison of three prediction rules in 1,436 participants showed that the detection rate of gastric cancer was significantly higher in the medium risk and high risk groups than that in the low risk group (p < 0.05, p2 < 0.001, p3 < 0.05) (Table 3), and the detection rate of early gastric cancer in the medium risk and high risk groups reached 90%, indicating that the three prediction rules can improve the detection rate of early gastric cancer. We noticed that all cases of advanced gastric cancer were diffuse-type lesions, which were detected in the low risk group for both the Scoring System from JPHC and Li’s Scoring System. Previous studies reported that these scoring systems did not perform well for diffuse-type gastric cancer [15-16].
One valuable role of prediction rules is to identify patients as low risk in order to avoid further testing and save medical resources. An ideal risk prediction rule would identify low risk patients of considerable size with a low detection rate of gastric cancer, to minimize missed diagnoses. However, it is worth noting that a number of studies mentioned that gastric cancer and precancerous lesions were detected in the low risk groups of several prediction rules. [16,20-21]. In our study, the Scoring System from JPHC identified the most patients as low risk (1096, 76.32%), followed by the ABC method (811, 56.48%), and Li’s Scoring System (37, 37.95%). The missed diagnosis rate of gastric cancer was the highest in the Scoring System from JPHC (1.19%), and 84.62% of the patients aged 60–79 years. Therefore, missed diagnoses should be especially considered for elderly patients when using this scoring system. The missed diagnosis rate of the ABC method was 0.99%, and all cases were males, which should be taken seriously. Furthermore, patients in group A with a history of H. pylori eradication may need gastroscopy. Miura et al. reported that about 20% patients with gastric cancer have a history of H. pylori eradication, and they have normal PG levels and negative anti-H. pylori IgG titres . Although Li’s Scoring System had the lowest rate of missed diagnosis (0.55%), all missed patients were females. Thus, it is still necessary to consider the missed diagnosis of female patients due to the assigned 0 points for females in Li’s scoring system.
In this study, the ABC method showed the least predictive capacity for gastric cancer with the lowest AUC (0.642, 95% CI: 0.617–0.667), which was significantly lower than that of the Scoring System from JPHC (p < 0.05). Moreover, the specificity was significantly lower than that of the Scoring System from JPHC (p < 0.001) and Li’s Scoring System (p < 0.001). Consistent with previous research, the ABC method for gastric cancer screening did not work well in the Chinese populations, with lower sensitivity and specificity than those in nonChinese studies [23-24]. This may be related to the fact that the ABC method was developed in Japanese populations, and the optimal PG and G-17 cut-off values may not be applicable to screening for gastric cancer in China. Furthermore, the ABC method only includes the results of serological indicators without demographic factors (e.g. age, sex, etc.) and lifestyle habits (e.g. smoking status, consumption of alcohol and high-sodium food, etc.), which may affect its predictive ability.
The Scoring System from JPHC had the highest AUC (0.745, 95% CI: 0.722–0.767), followed by Li’s Scoring System (0.739, 95% CI: 0.715–0.761), and these two prediction rules performed similarly. However, the Scoring System from JPHC had the largest possibility of missed diagnosis of gastric cancer with the lowest sensitivity(53.57%) and NPV(98.90%)， which may be possibly explained by the weight setting of indicators (e.g. H. pylori infection) and regional differences. The Scoring System from JPHC was developed based on a large group of Japanese participants and included a number of variables, such as demographic factors, lifestyle, and the risk categories of the ABC method. Furthermore, the optimal cut-off values of PG and G-17 may be inappropriate for screening in China . The scoring system did not find any substantial difference between the risk of individuals in categories C and D of the ABC method, which were similar to several published studies [25-26]. Nevertheless, the scoring system emphasized the important effect of smoking and high sodium food consumption on the occurrence of gastric cancer, and the quantification of these lifestyle-related risk factors might provide an incentive for adopting healthier lifestyles, particularly for high-risk individuals .
Li’s Scoring System performed well in predicting the risk of gastric cancer and having the lowest probability of missed diagnosis with the modest AUC (0.739), and highest sensitivity (85.71%) and NPV (99.50%). These results are similar to the originally published values . The prediction rule was developed based on a multicenter, large-sample Chinese population, and the cut-off values of PG and G-17 were more in line with screening for gastric cancer in China. For example, the cut-off value of PGR in Li’s Scoring System and the Scoring System from JPHC is 3.89 and 3, respectively. However, it is worth noting that the efficacy of Li’s Scoring System should be further verified in order to improve discrimination and reduce missed diagnosis of females. H. pylori infection has been considered as the key cause of intestinal gastric cancer, and the efficacy of screening may be improved by distinguishing two types of H. pylori strains (strains expressing CagA and VacA, and strains without CagA and VacA).
Our study had potential limitations. First, we studied the ABC method, the Scoring System from JPHC, and Li’s Scoring System, although several other prediction rules are available [28,17]. Second, we only compared the efficacy of three prediction rules, and did not analyze possible risk factors (e.g., obesity and the consumption of fried food, etc.), which could be done by gathering more cases in future studies. Finally, the sample size was small. We only included 1436 health examination populations, suggesting Chinese are poorly informed about gastric cancer screening and the education on this topic is needed.