The Fast Track FIT study : diagnostic accuracy of faecal immunochemical test for haemoglobin in patients with suspected colorectal cancer

BACKGROUND: The faecal immunochemical test (FIT) is now available to support clinicians in the assessment of patients at low risk of colorectal cancer (CRC) and within the Bowel Cancer Screening Programme. AIM: To determine the diagnostic accuracy of FIT for CRC and clinically significant disease in patients referred because they were judged by their GP to fulfil NICE NG12 criteria for suspected CRC. DESIGN AND SETTING: Patients referred from primary care with suspected CRC, meeting NG12 criteria, to 12 secondary care providers in Yorkshire and Humber were asked to complete a FIT prior to investigation. METHOD: The diagnostic accuracy of FIT based upon final diagnosis was evaluated using receiver operating characteristics analysis. Clinicians and patients were blinded to the FIT results. RESULTS: 5040 patients were fully evaluated and CRC was detected in 151 (3%). An optimal cut-off value of 19 g Hb/g faeces for CRC was determined, giving a sensitivity of 85.4% (78.8-90.6%) and specificity of 85.2% (84.1-86.2%). The negative predictive value at this cut-off value was 99.5% (99.2-99.7%) and the positive predictive value 15.1% (12.8-17.7%). Sensitivity and specificity of FIT for CRC and significant premalignant polyps at this cut-off value were 62.9% (57.5-68.0%) and 86.4% (85.4-87.4%) respectively and when including all organic enteric disease were 35.7% (32.9-38.5%) and 88.6% (87.5-89.6%). CONCLUSIONS: FIT used in patients fulfilling NICE NG12 criteria should allow for a more personalised CRC risk assessment. FIT should permit effective, patient-centred decision-making to inform the need for, type and timing of further investigation.