Fecal immunochemical test accuracy in familial risk colorectal cancer screening

There is little information on fecal immunochemical test (FIT) in familial risk colorectal cancer (CRC) screening. Our study assesses FIT accuracy, number needed to scope (NNS) and cost to detect a CRC and an advanced neoplasia (AN) in this setting. We performed a multicentric, prospective, double-blind study of diagnostic tests on individuals with first-degree relatives (FDRs) with CRC submitted to screening colonoscopy. Two stool samples were collected and fecal hemoglobin in the first sample (FIT1) and the highest in both samples (FITmax) were determined. Areas under the curve (AUC) for CRC and AN as well as the best FIT1 and FITmax cutoff value for CRC were determined. At this threshold, NNS and the cost per lesion detected were calculated. A total of 595 individuals were included (one FDR > 60 years, 413; two FDR or one ≤ 60 years, 182). AN and CRC were found in 64 (10.8%) and six (1%) patients, respectively. For CRC diagnosis, FIT1 AUC was 0.96 [95% confidence interval (CI): 0.95-0.98] and FITmax AUC was 0.95 (95% CI: 0.93-0.97). For AN diagnosis, FIT1 and FITmax AUC were 0.74 (95% CI: 0.66-0.82). The best cutoff point for CRC was 115. At this threshold, the NNS to detect a CRC was 5.67 and 7.67, and the cost per CRC was 1,064€ and 1591.33€ on FIT1 and FITmax strategies, respectively. FIT shows high accuracy to detect CRC in familial CRC screening. Performing two tests does not improve diagnostic accuracy, but increases cost and NNS to detect a lesion.