ABSTRACT
Introduction Faecal immunochemical testing (FIT) has been shown to have an acceptable positive predictive value (PPV) and negative predictive value (NPV) for the detection of colorectal cancer (CRC). NHS-E/NICE COVID pandemic guidance recommends that patients with a FIT < 10μgHb/g do not need urgent colonic imaging but can be 'safety-netted' if not anaemic. Nonetheless concerns remain, that based on a FIT test alone up to 10% of patients with CRC might be missed by this approach, possibly due to the inherent risks of sampling error. The AIM of this study was to determine if the NPV and PPV of FIT could be improved by a strategy of duplicate FIT testing. Methods An observational cohort study of duplicate FIT testing of all patients referred on a Lower GI TWW pathway across 4 NHS provider trusts in the Lancashire and South Cumbria Cancer alliance from Jan2019-Feb 2021. FIT samples were analysed at a single centre using OC-sensor with a cut off > 10 0μgHb/g of faeces taken as a positive. CRC diagnoses were ascertained from local hospital records and cross referenced with the Somerset Cancer Registry. Results 28,622 of 30,105 (95%) referred patients (median [range] age 66y [16-103], 56% female) submitted duplicate FIT tests. 317/28,622 (1.1%) were diagnosed with CRC, of whom 22/317 (59%) were men. Of 18,952/28622 (66%) with two negative FIT tests, CRC was subsequently diagnosed in 7 patients (0.04%) with anaemia (n=7) and right sided tumours (n=6). In contrast, a single FIT strategy would have missed 22 patients of whom only 7 (32%) were anaemic. Interestingly duplicate FIT testing also improved the PPV, which increased from 0.3% if both tests were >10 - 100 0μgHb/g to a PPV of 14% if both tests were >100 0μgHb/g of faeces Conclusions A strategy of duplicate testing improves the NPV and PPV of FIT and should be considered as a mitigation to reducing missed cancer diagnosis. In patients at risk of CRC with no anaemia, duplicate FIT testing effectively rules out CRC and allows patients to be safely managed in primary care.
ABSTRACT
Background: The COVID19 pandemic has resulted in a significant reduction in referrals to the colorectal cancer 2-week wait pathway. The aim of this study was to describe this 'missing cohort of referrals' by comparing the characteristics of referrals made during the pandemic with historic referrals. Methods: Demographics, index of multiple deprivation deciles (IMD), labs, faecal immunochemical tests (FIT) and cancer outcomes data of referrals between January 2015 and September 2020 were included. The historic cohort (Jan 2015 to Feb 2020) was compared with the pandemic cohort (Apr to Sep 2020). Referrals made in March 2020 were excluded. Results: 16704 referrals were included -14800 historic, 1583 pandemic and 321 excluded. There was no difference in age (median 69 years), gender (47% male), ethnicity (95% Caucasian), IMD (median 7) or cancer incidence (any malignancy 4.7% vs 5.0%, colorectal cancer 3.1% vs 3.9%). There were fewer referrals with iron-deficiency anaemia (11% vs 15%, P < 0.01) due to introduction of a separate pathway in 2019. FIT testing doubled during the pandemic (64% vs 31% in 2019, P < 0.001) after it was made mandatory. Conclusion: Clinical risk and outcome characteristics of pandemic referrals did not differ significantly from historic referrals. They were neither a selective high-risk cohort due to improved triage nor a low-risk cohort because of concerns of high-risk patients attending hospital during the pandemic. The 'missing cohort' are likely to have similar clinical characteristics as historic referrals including 5% cancer incidence and 10% polyp incidence. Urgent action is required to avoid further harm to these patients.