Positivity threshold (I-FOBT ng/ml) | Positivity rate (%)* | Adenoma ⩾10 mm or high grade dysplasia (RSN†) | Colorectal cancer | Advanced neoplasia (colorectal cancer or adenoma⩾10 mm or high grade dysplasia) | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|
PPV | RSN† | RFP‡ | FP:TP§ | PPV | RSN† | RFP‡ | FP:TP§ | ||||
G-FOBT, guaiac faecal occult blood test; I-FOBT, immunochemical faecal occult blood test; PPV, predictive positive value; RFP, ratio of false positive rate; RSN, ratio of sensitivity. | |||||||||||
Values for RSN, RFP and FP:TP are mean [95% confidence interval]. | |||||||||||
*Patients with both analysable tests, independent of whether or not a colonoscopy was performed or not (n = 887). | |||||||||||
†RSN>1, sensitivity of I-FOBT is greater than that of G-FOBT. | |||||||||||
‡RFP>1, false positive rate of I-FOBT is greater than that of G-FOBT, the specificity of I-FOBT is therefore inferior to G-FOBT. | |||||||||||
§FP:TP, number of extra false positives associated with the detection of one extra true disease case using I-FOBT instead of G-FOBT. | |||||||||||
I-FOBT | 20 ng/ml | 6.9 | 3.56 [2.66–4.77] | 4.0 | 1.50 [1.11–2.03] | 2.88 [2.46–3.36] | 47.43 [22.32–100.80] | 30.2 | 3.02 [2.38–3.84] | 2.68 [2.24–3.22] | 2.17 [1.65–2.85] |
50 ng/ml | 3.3 | 2.08 [1.63–2.64] | 7.7 | 1.36 [0.99–1.87] | 1.28 [1.08–1.53] | 10.00 [2.86–34.97] | 44.7 | 2.33 [1.73–3.14] | 0.99 [0.79-1.23] | – | |
75 ng/ml | 2.4 | 1.70 [1.33–2.16] | 8.7 | 1.14 [0.83–1.58] | 0.94 [0.78–1.14] | – | 49.2 | 1.90 [1.41–2.56] | 0.67 [0.53–0.86] | – | |
G-FOBT | 2.4 | 7.3 | 27.7 |