Service evaluation of faecal immunochemical testing and anaemia for risk stratification in the 2-week-wait pathway for colorectal cancer.

ABSTRACT

Background: New national guidance on urgent referral for investigation of colorectal cancer included faecal occult blood testing in 2015. A service evaluation of faecal immunochemical testing (FIT) and anaemia as risk stratification tools in symptomatic patients suspected of having CRC was undertaken. Methods: Postal FIT was incorporated into the colorectal cancer 2-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 recorded prospectively. Anaemia was defined as a haemoglobin level below 120 g/l in women and 130 g/l in men. Results: FIT kits were sent to 1106 patients, with an 80·9 per cent return rate; 810 patients completed investigations and 40 colorectal cancers were diagnosed (4·9 per cent). FIT results were significantly higher in patients with anaemia (median (i.q.r.) 4·8 (0·8-34·1) versus 1·2 (0-6·4) µg Hb/g faeces in those without anaemia; P < 0·001). Some 60·4 per cent of patients (538 of 891) had a result lower than 4 µg haemoglobin (Hb) per g faeces (limit of detectability), and 69·7 per cent (621 of 891) had less than 10 µg Hb/g faeces. Some 60 per cent of patients with colorectal cancer had a FIT reading of 150 µg Hb/g faeces or more. For five colorectal cancers diagnosed in patients with a FIT value below 10 µg Hb/g faeces, there was either a palpable rectal mass or the patient was anaemic. A FIT result of more than 4 µg Hb/g faeces had 97·5 per cent sensitivity and 64·5 per cent specificity for a diagnosis of colorectal cancer. A FIT result above 4 µg Hb/g faeces and/or anaemia had a 100 per cent sensitivity and 45·3 per cent specificity for colorectal cancer diagnosis. Conclusion: FIT is most useful at the extremes of detectability; strongly positive readings predict high rates of colorectal cancer and other significant pathology, whereas very low readings in the absence of anaemia or a palpable rectal mass identify a group with very low risk. High return rates for FIT within this 2WW pathway indicate its acceptability.