Evaluating the Use of Faecal Immunochemical Testing (Fit) in the Urgent Suspected Colorectal Cancer Pathway during the Sars-Cov- 2 Pandemic

ABSTRACT

Aim: UK endoscopy services faced challenges prior to SARS-CoV- 2. During the first months of the pandemic, activity fell by 92%. Consequently, in June 2020, NHS England recommended Faecal immunochemical testing (FIT) for all symptomatic patients to rationalise endoscopy. This study sought to evaluate the real-world safety and effectiveness of this approach. Method(s) Patients referred with suspected colorectal cancer (CRC) on the two-week wait (2ww) pathway were asked to complete a FIT. Samples were analysed using the OC-Sensor. While a FIT > 100 mug Hb/g was used to prioritise investigation, all patients were subsequently investigated. FIT results were correlated with diagnostic studies. Result(s) Between January to December 2020, 48% of referred patients had a FIT. 26% was above the threshold of 10 mug Hb/g in and 8.6% above 100mug Hb/g. 347 patients also had a positive FIT but were not referred. The sensitivity, specificity, NPV, PPV, and likelihood ratio at a threshold of 10mug Hb/g were 78.6%(95%CI0.69-0.86%), 36.8%(95%CI0.34-0.39%), 7.1%(95%CI0.057-0.088%), 96.5% (95%CI 0.95-0.98%) and 1.24 respectively. At 100mug Hb/g, this was 37.8%(95%CI0.29-0.48%), 80.2%(95%CI0.78-0.82%), 10.5%(95%CI0.077-0.14%), 95.4%(95%CI0.94-0.96%) and 1.9 respectively. Conclusion(s) FIT shows promise in trials, but our data raises concerns about real-world performance. Only 48% of patients completed FIT before referral, and we are exploring why 347 FIT-positive patients were not referred. While results are broadly congruent with reported literature that suggested 10% of CRC are FIT negative, this is greater in our cohort at 25%. This raises concerns about the safety of discharging patients based on FIT alone. Modifying the FIT threshold may be required and improving safety-netting where FIT is known to be ineffective, such as patients with iron deficiency anaemia.