Fecal immunochemical test accuracy in average-risk colorectal cancer screening

Abstract

Aim: To assess the fecal immunochemical test (FIT) accuracy for colorectal cancer (CRC) and advanced neoplasia (AN) detection in CRC screening.

Methods: We performed a multicentric, prospective, double blind study of diagnostic tests on asymptomatic average-risk individuals submitted to screening colonoscopy. Two stool samples were collected and the fecal hemoglobin concentration was determined in the first sample (FIT1) and the highest level of both samples (FITmax) using the OC-sensor™. Areas under the curve (AUC) for CRC and AN were calculated. The best FIT1 and FITmax cut-off values for CRC were determined. At this threshold, number needed to scope (NNS) to detect a CRC and an AN and the cost per lesion detected were calculated.

Results: About 779 individuals were included. An AN was found in 97 (12.5%) individuals: a CRC in 5 (0.6%) and an advanced adenoma (≥ 10 mm, villous histology or high grade dysplasia) in 92 (11.9%) subjects. For CRC diagnosis, FIT1 AUC was 0.96 (95%CI: 0.95-0.98) and FITmax AUC was 0.95 (95%CI: 0.93-0.97). For AN, FIT1 and FITmax AUC were similar (0.72, 95%CI: 0.66-0.78 vs 0.73, 95%CI: 0.68-0.79, respectively, P = 0.34). Depending on the number of determinations and the positivity threshold cut-off used sensitivity for AN detection ranged between 28% and 42% and specificity between 91% and 97%. At the best cut-off point for CRC detection (115 ng/mL), the NNS to detect a CRC were 10.2 and 15.8; and the cost per CRC was 1814€ and 2985€ on FIT1 and FITmax strategies respectively. At this threshold the sensitivity, NNS and cost per AN detected were 30%, 1.76, and 306€, in FIT1 strategy, and 36%, 2.26€ and 426€, in FITmax strategy, respectively.

Conclusion: Performing two tests does not improve diagnostic accuracy, but increases cost and NNS to detect a lesion.

Trial registration: ClinicalTrials.gov NCT00906997.

Keywords: Adenoma; Colorectal neoplasms; Cost-benefit analysis; Early detection of cancer; Occult blood; Sensitivity and specificity.

Figure 1

Fecal hemoglobin (ng/mL) according to the most advanced lesion. Values expressed as mean ± SD. Mann-Withney test. FIT: Fecal immunochemical test; FIT1: Fecal hemoglogin concentration in the first stool sample; FITmax: Highest fecal hemoglobin concentration of two stool samples.

Figure 2

Receiver operating characteristics curves of fecal immunochemical test-1 and -max for advanced neoplasia and invasive cancer. FIT: Fecal immunochemical test; FIT1: Fecal hemoglogin concentration in the first stool sample; FITmax: Highest fecal hemoglobin concentration of two stool samples; AUC: Area under the curve. ¹P = 0.034 with respect to FITmax in the homogeneity area test.