What is the role of iFOBT in screening for colorectal cancer?

CB7080, University of North Carolina, Chapel Hill, NC 27599-7080, USA.
Gut (Impact Factor: 13.32). 11/2007; 56(10):1343-4. DOI: 10.1136/gut.2007.124107
Source: PubMed
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    ABSTRACT: In the present work we investigated the possible role of the native fluorescence of blood plasma in the management of colorectal cancer (CRC) and its feasibility as a new tumor marker. Sample of blood was collected from 248 asymptomatic blood donors and from 246 CRC patients. The native fluorescence of blood plasma was measured using a conventional spectrofluorimeter. The intensity of fluorescence of blood plasma at 623 nm (IF623), reasonably ascribed to endogenous porphyrins, was significantly higher in CRC patients than in healthy subjects. The diagnostic capability of IF623 in the discrimination between healthy subjects and CRC patients was tested by Receiving Operating Characteristic (ROC) curve analysis, which resulted in an Area Under the Curve (AUC) of 0.72+/-0.01. Fluorescence measurement of blood plasma might be considered diagnostically useful as a candidate for a new tumor marker for CRC management. The procedure is characterised by a great acceptability and by a very low cost, and might be used in a two-step screening wherein an IF623 positive result is followed by colonoscopy.
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    ABSTRACT: Adjusting the threshold for positivity of quantitative fecal immunochemical tests (FIT) allows for controlling the number of follow-up colonoscopies in a screening program. However, it is unknown to what extent higher cutoff levels affect detection rates of screen-relevant neoplasia. This study aimed to assess the effect of higher cutoff levels of a quantitative FIT on test positivity rate and detection rate of early-stage colorectal cancers (CRC). Subjects above 40 years old scheduled for colonoscopy in 5 hospitals were asked to sample a single FIT (OC sensor) before colonoscopy. Screen-relevant neoplasia were defined as advanced adenoma or early-stage cancer (stage I and II). Positivity rate, sensitivity, and specificity were evaluated at increasing cutoff levels of 50 to 200 ng/mL. In 2,145 individuals who underwent total colonoscopy, 79 patients were diagnosed with CRC, 38 of which were with early-stage disease. Advanced adenomas were found in 236 patients. When varying cutoff levels from ≥ 50 to ≥ 200 ng/mL, positivity rates ranged from 16.5% to 10.2%. With increasing cutoff levels, sensitivity for early-stage CRCs and for screen-relevant neoplasia ranged from 84.2% to 78.9% and 47.1% to 37.2%, respectively. Higher FIT cutoff levels substantially decrease test positivity rates with only limited effects on detection rates of early-stage CRCs. However, spectrum bias resulting in higher estimates of sensitivity than would be expected in a screening population may be present. Higher cutoff levels can reduce strain on colonoscopy capacity with only a modest decrease in sensitivity for curable cancers.
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