A service evaluation of FIT and anaemia for risk stratification in the two week wait pathway for colorectal cancer

Introduction: New national guidance on urgent referral for investigation for Colorectal Cancer (CRC) included faecal occult blood testing in 2015. We evaluated faecal immunochemical testing (FIT) and anaemia as risk stratification tools in symptomatic patients suspected of having CRC.Methods: Postal FIT was incorporated into the CRC two week wait (2WW) pathway for all patients without rectal bleeding in 2016. Patients were investigated in the 2WW pathway as normal and outcomes of investigations were prospectively recorded. Anaemia was defined as haemoglobin less than 120g/L in women and less than 130g/L in men.Results: FIT kits were sent to 1106 patients with an 80.9% return rate; 810 patients completed investigation with 40 CRCs diagnosed (4.9%). Median FIT results were significantly higher in patients who were anaemic (median 4.8 iqr 0.8-34.1 versus 1.2 iqr 0-6.4, Mann-Whitney p less than 0.001).Some 538 (60.4%) had a result of less than 4 µgHb/gFaeces (limit of detectability) and 621 (69.7%) a result less than 10 µgHb/gFaeces. Sixty per cent of CRCs had a FIT reading of >150 µgHb/gFaeces. Five CRCs diagnosed in patients with a FIT4 µgHb/gFaeces had 97.5% sensitivity and 64.5% specificity for CRC diagnosis. A FIT result of >4 µgHb/gFaeces and/or anaemia had a 100% sensitivity and 45.3% specificity for CRC diagnosis.Conclusion: FIT is most useful at the extremes of detectability; strongly positive readings predict high rates of CRC and other significant pathology, whilst very low readings in the absence of anaemia or palpable rectal mass identify a group with very low risk. High return rates for FIT within this 2WW pathway indicate its acceptability.