Diagnostic accuracy of the faecal immunochemical test for colorectal cancer in symptomatic patients: comparison with NICE and SIGN referral criteria

Aim The diagnostic accuracy of the faecal immunochemical test (FIT) at a 100 ng/ml threshold for colorectal cancer (CRC) was compared with National Institute for Health and Care Excellence (NICE) and the Scottish Intercollegiate Guidelines Network (SIGN) referral criteria. Method A multicentre, prospective, blind study of diagnostic tests was carried out in two Spanish health areas. In 787 symptomatic patients referred for a diagnostic colonoscopy, we determined whether patients met NICE and SIGN referral criteria. All patients performed one FIT determination (OCsensor (TM)). The sensitivity and specificity for CRC detection were determined with McNemar's test. The diagnostic odds ratio as well as the number needed to scope (NNS) to detect a CRC were calculated. Results We detected CRC in 97 (12.3%) patients; 241 (30.6%) had an FIT >= 100 ng/ml and 300 (38.1%) and 473 (60.1%) met NICE and SIGN referral criteria. The FIT had a higher sensitivity for CRC detection than NICE criteria (87.6%, 61.9%; P < 0.001) and SIGN criteria (82.5%; P = 0.4). The specificity of FIT was also higher than NICE and SIGN criteria (77.4%, 65.2%, 42.7%; P < 0.001). The odds ratios of FIT, NICE and SIGN criteria for the diagnosis of CRC were 24.24 (95% CI 12.91-45.53), 3.04 (95% CI 1.96-4.71) and 3.51 (95% CI 2.03-6.06). The NNS to detect a CRC in individuals with an FIT = 100 ng/ml was 2.83 (95% CI 2.4-3.41) and in individuals who met NICE and SIGN criteria it was 5 (95% CI 3.98-6.37) and 5.95 (95% CI 4.85-7.35). Conclusion Our study suggests that FIT is more accurate for the detection of CRC than the current NICE and SIGN referral criteria in symptomatic patients referred for colonoscopy.