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.

Early clinical outcomes of a rapid colorectal cancer diagnosis pathway using faecal immunochemical testing in Nottingham

“…In this dataset the proportion of FIT results of < 4.0 μg Hb/g faeces is higher than during our pilot , confirming that direct GP access to FIT does enable ‘opportunistic screening’. This is further evident in the wide age range of patients who returned a FIT kit, with patients as young as 18 being tested.…”

“…We have previously described our straight to test (STT) pathway and our FIT pilot . A number of locally agreed modifications were required to integrate FIT into clinical pathways (Appendix in the online Supporting Information): Primary care colleagues had direct access to FIT.…”

“…All such results are electronically notified to the STT team by the BCSP hub as soon as they are analysed. This threshold was used in our pilot to identify those patients with the highest risk of CRC and this cut‐off was preselected for our previous pilot as an approximate equivalent to a positive gFOBT – the only alternative in clinical practice at the time ;…”

“…Faecal Hb concentrations were determined and categorized as ≥ 150.0 μg Hb/g faeces (high risk positive – rapid), 10.0–149.9 μg Hb/g faeces (standard risk – 2WW), 4.0–9.9 μg Hb/g faeces with anaemia (standard risk – 2WW) and without anaemia (negative), and < 4.0 μg Hb/g faeces (negative) as per our ‘Getting FIT’ pilot . A result of 4.0 μg Hb/g faeces represents the limit of quantification in our laboratory, i.e.…”

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“…Thus, the existing DG30 system and test‐kit allocation could be scaled up to include patients with high risk symptoms. A referral system based entirely on FIT will miss cancers; but with a negative predictive value ranging between 99·1 and 99·8 per cent this may be deemed acceptable in the current environment. The London pathway involves referring only FIT‐positive patients at a threshold over 10 μg Hb/g faeces for investigation; patients with more than 150 μg Hb/g faeces should be prioritized for colonoscopy.…”