Effect of biopsies on sensitivity and specificity of ultra-rapid urease test for detection of Helicobacter pylori infection: A prospective evaluation

Table 1 Ultra-rapid urease test results at various time intervals comparing one vs two antral biopsies in 53 patients

		1 m	5 m	10 m	20 m	30 m	60 m	2 h	3 h	24 h
True positive	1 Bx	1	9	13	18	20	23	23	24	24
	2 Bx	3	14	17	21	23	24	24	24	27
True negative	1 Bx	25	25	25	25	25	25	25	25	24p
	2 Bx	25	25	25	25	25	25	25	25	23
False positive	1 Bx	0	0	0	0	0	0	0	0	1
	2 Bx	0	0	0	0	0	0	0	0	2
False negative	1 Bx	27	19	15	10	8	5	5	4	1
	2 Bx	25	14	11	7	5	4	4	4	1
Sensitivity (%)	1 Bx	3.6	32.1	46.4	64.3	71.4	82.1	82.1	85.7	96.4
	2 Bx	10.7	50	60.7	75	82.1	85.7	85.7	85.7	96.4
Specificity (%)	1 Bx	100	100	100	100	100	100	100	100	96
	2 Bx	100	100	100	100	100	100	100	100	92
PPV (%)	1 Bx	100	100	100	100	100	100	100	100	96.4
	2 Bx	100	100	100	100	100	100	100	100	96.4
NPV (%)	1 Bx	48.1	55.6	62.5	71.4	75.8	83.3	83.3	86.2	96
	2 Bx	50	64.1	69.4	78.1	83.3	86.2	86.2	86.2	95.8

Bx = Biopsy, m = minutes, h = hours, PPV = positive predictive value, NPV = negative predictive value.