Table 3 The performance characteristics of the iFOBT, OC-Sensor, at different cutoff levels

	Cutoff values (ng ml⁻¹)
	50	75	100	125	150	175	200	225
Positives adherent to colonoscopy ^a (N)	428	336	280	248	234	215	198	187
Colonoscopy rate^b (%)	7.0%	5.5%	4.5%	4.0%	3.8%	3.5%	3.2%	3.0%
Number of lesions (n)
Colorectal cancer	28	27	24	24	24	24	24	23
CRC+advanced adenomas	189	163	145	136	131	121	113	109
Detection rate^c (%)
Colorectal cancer	0.45%	0.44%	0.39%	0.39%	0.39%	0.39%	0.39%	0.37%
Confidence interval (95% CI)	0.3–0.6%	0.3–0.6%	0.2–0.6%	0.2–0.6%	0.2–0.6%	0.2–0.6%	0.2–0.6%	0.2–0.5%
CRC+advanced adenomas	3.1%	2.6%	2.4%	2.2%	2.1%	2.0%	1.8%	1.8%
Confidence interval (95% CI)	2.6–3.5%	2.3–3.1%	2–2.7%	1.8–2.6%	1.8–2.5%	1.6–2.3%	1.5–2.2%	1.4–2.1%
Number Needed To Scope ^d (N/n)
Colorectal cancer	15.3	12.4	11.7	10.3	9.8	9.0	8.3	8.1
Confidence interval (95% CI)	11.3–23.8	9.1–19.5	8.4–18.9	7.5–16.7	7.1–15.7	6.5–14.4	6–13.2	5.9–13.2
CRC+advanced adenomas	2.3	2.1	1.9	1.8	1.8	1.8	1.8	1.7
Confidence interval (95% CI)	2.6–2.5	1.9–2.3	1.7–2.2	1.6–2.1	1.6–2	1.6–2	1.6–2	1.5–2
Specificity ^e
CRC+advanced adenomas	96.0%	97.1%	97.8%	98.1	98.3	98.4	98.6	98.7
Confidence interval (95% CI)	95.5–96.5%	96.7–97.5%	97.4–98.1%	97.8–98.5%	98.0–98.6%	98.1–98.8%	98.3–98.9%	98.4–99.0%
CRC miss rate^f (%)	N.A.	3.6%	14.3%	14.3%	14.3%	14.3%	14.3%	17.9%
Confidence interval (95% CI)	N.A.	−3.3–10.4%	1.3–27.2%	1.3–27.2%	1.3–27.2%	1.3–27.2%	1.3–27.2%	3.7–32%

Abbreviations: CI, confidence interval; CRC, colorectal cancer; iFOBT, immunochemical faecal occult blood test.
^aPostives adherent to colonoscopy=patients with a positive iFOBT who underwent a colonoscopy.
^bColonoscopy rate=percentage of participants with a positive iFOBT who underwent a colonoscopy.
^cDetection rate=percentage of participants with lesions of reference.
^dNumber Needed To Scope=the number of patients to find one extra patient with lesions of reference.
^eSpecificity was calculated under the rare disease assumption (Brecht and Robra, 1987).
^fCRC miss rate=the percentage of the colorectal cancer patients at that cutoff relative to the colorectal cancer patients at the minimal 50 ng ml⁻¹ cutoff.

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