Serum Helicobacter pylori KatA and AhpC antibodies as novel biomarkers for gastric cancer

Table 3 Sensitivity and specificity of different catalase and alkyl hydroperoxide reductase critical values

Percentile1	All subjects			H. pylori positive subjects			H. pylori negative subjects
	Critical value (OD)2	Sensitivity	Specificity	Critical value (OD)2	Sensitivity	Specificity	Critical value (OD)2	Sensitivity	Specificity
KatA
Optimal cutoff point2	0.3583	66.81%	86.36%	0.3557	64.39%	88.14%	0.3730	70.79%	83.85%
25%	0.2800	46.55%	93.18%	0.4152	69.70%	74.58%	0.2773	50.56%	90.00%
50%	0.4305	75.00%	71.59%	0.5133	87.12%	49.15%	0.4447	78.65%	69.23%
75%	0.5958	90.95%	36.36%	0.6692	93.94%	24.58%	0.6107	92.13%	36.15%
90%	0.7418	97.84%	16.29%	0.9042	100.00%	8.47%	0.7873	97.75%	14.62%
AhpC
Optimal cutoff point2	0.3647	75.65%	45.49%	0.3613	75.76%	48.31%	0.2330	43.82%	70.77%
25%	0.1953	30.43%	78.95%	0.1953	30.30%	80.51%	0.1917	30.34%	77.69%
50%	0.2830	59.57%	57.14%	0.2865	59.85%	60.17%	0.2913	62.92%	57.69%
75%	0.4267	84.35%	32.71%	0.4325	83.33%	33.05%	0.4313	85.39%	23.85%
90%	0.5747	95.65%	14.29%	0.5302	93.94%	13.56%	0.6410	96.63%	13.85%

¹Percentiles of serum KatA and AhpC antibody levels in controls;

²Optimal cutoff point in the different parameters was identified according to the maximum Youden’s index (sensitivity + specificity - 1). H. pylori: Helicobacter pylori; KatA: Catalase; AhpC: Alkyl hydroperoxide reductase.