An observational study of replicate faecal immunochemical tests in the urgently referred symptomatic cohort.

INTRODUCTION: Triage of patients with suspected colorectal cancer (CRC) utilises a single faecal immunochemical test (FIT) at a defined threshold. Limited evidence exists regarding whether replicate FIT improves the positive and negative predictive value in symptomatic patients. This study examines urgently referred symptomatic patients undergoing replicate FIT. Primary aim is to assess two FITs and CRC/serious bowel disease. Secondary aims are to determine correlation and utility of replicate FIT. METHODOLOGY: Patients carried out one additional FIT during COVID-19 pandemic. FIT 1 and FIT 2 (the replicate sample) were analysed in relation to symptoms, diagnoses, investigations, future colonoscopy and missed CRC. Study period was 01/03/2020-31/07/2020. Three subgroups were compared; double positive (≥10 µg Hb/g faeces), double negative, and discordant FIT (one positive). RESULTS: 111 patients had replicate FIT (50 male, 61 female). 43 (38.7%) patients had double negative, 32 (28.8%) double positive and 36 (32.4%) had discordant FITs. Median time between FITs was 14 days (IQR = 11-19). 83% of double positive patients underwent colonoscopy/virtual colonoscopy (61% in double negative patients). Six CRC and one high-risk polyp were in double positive patients (none in other groups). One discordant patient was not investigated and a CRC missed. CONCLUSIONS: Replicate FIT as a triage strategy appears most effective where both FITs are negative. CRC risk is low when FIT results are discordant. Double negative FITs are reassuring given benign associated diagnoses, or for patients where endoscopic investigation is high-risk. Larger studies are required to evaluate discordant FITs, enabling refinement of urgent investigation pathways.

Comparison of faecal calprotectin using two collection and extraction strategies for the BÜHLMANN CALEX® Cap - possible implications for clinical cut-offs?

BACKGROUND: Faecal calprotectin has been identified as a useful biochemical marker in the differentiation of inflammatory bowel disease and irritable bowel syndrome. Typically, patients send faecal specimens in a pot for manual extraction by the laboratory. During the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) pandemic, the routine laboratory service was temporarily suspended due to the potential increased risk to staff. In this study we investigated the possibility of patients collecting samples directly into the faecal extraction tubes. METHOD: Patients submitted paired faecal samples for calprotectin analysis using a standard faecal container (current practice) and followed instructions for faecal collection using the BÜHLMANN CALEX® Cap device. Samples were returned to the laboratory immediately after collection. Laboratory staff manually extracted the calprotectin from the faecal samples using the CALEX® Cap prior to analysis of both extracts on the Cobas c702. RESULTS: 91 paired faecal samples were included in the study. Clinical correlation was found to be 70% with numerical correlation showing a positive bias for the patient-collected CALEX® Cap sample when compared to the laboratory-extracted faecal sample around the clinical decision points 100-250 µg calprotectin/g faeces. CONCLUSION: The study shows that collection of a faecal sample using the CALEX® Cap works well and is a good alternative to using standard containers. The correlation gives rise to the possibility that faecal calprotectin is not stable when collected into standard collection containers. Prior to further roll-out of this process, questions surrounding the current cut-offs would need to be addressed.

Replicate and repeat faecal immunochemical tests in symptomatic patients: A systematic review.

BACKGROUND: Faecal Immunochemical tests (FITs) in the assessment of patients presenting with symptoms have generally used a single sample. Little evidence pertains to the use of replicate, where a number of tests are done prior to decision-making or repeat FIT, where additional FIT are performed following clinical decision-making. Overwhelmingly, research has focussed on FIT to help identify colorectal cancer (CRC). The aim of this review is to assess the available literature concerning replicate and repeat FIT in symptomatic patients to help generate consensus and guide future research. METHODS: The terms 'faecal immunochemical test' or 'FIT' were combined with 'multiple' or 'repeat'. EMBASE, Medline and PubMed database and other searches were conducted. All papers published in English were included with no exclusion date limits until November 2021. RESULTS: Of the 161 initial papers screened, seven were included for review. Qualitative and quantitative FIT outcomes were assessed in the studies. The primary aims of most related to whether replicate FIT increased diagnostic yield of CRC, with colonoscopy used as the reference standard. One publication assessed the impact of a new COVID-adapted pathway on CRC detection. No consensus on replicate FIT was apparent. Some concluded that FITs may help minimise missed CRC diagnoses: others showed no increase in diagnostic yield of CRC. CONCLUSIONS: Current evidence on replicate and repeat FIT is both minimal and conflicting. FIT is a superb clinical tool, but significant gaps surrounding application remain. Further studies relating to replicate and repeat FIT are required.

Impact of changes to the interscreening interval and faecal immunochemical test threshold in the national bowel cancer screening programme in England: results from the FIT pilot study.

INTRODUCTION: The NHS Bowel Cancer Screening Programme (BCSP) faces endoscopy capacity challenges from the COVID-19 pandemic and plans to lower the screening starting age. This may necessitate modifying the interscreening interval or threshold. METHODS: We analysed data from the English Faecal Immunochemical Testing (FIT) pilot, comprising 27,238 individuals aged 59-75, screened for colorectal cancer (CRC) using FIT. We estimated screening sensitivity to CRC, adenomas, advanced adenomas (AA) and mean sojourn time of each pathology by faecal haemoglobin (f-Hb) thresholds, then predicted the detection of these abnormalities by interscreening interval and f-Hb threshold. RESULTS: Current 2-yearly screening with a f-Hb threshold of 120 µg/g was estimated to generate 16,092 colonoscopies, prevent 186 CRCs, detect 1142 CRCs, 7086 adenomas and 4259 AAs per 100,000 screened over 15 years. A higher threshold at 180 µg/g would reduce required colonoscopies to 11,500, prevent 131 CRCs, detect 1077 CRCs, 4961 adenomas and 3184 AAs. A longer interscreening interval of 3 years would reduce required colonoscopies to 10,283, prevent 126 and detect 909 CRCs, 4796 adenomas and 2986 AAs. CONCLUSION: Increasing the f-Hb threshold was estimated to be more efficient than increasing the interscreening interval regarding overall colonoscopies per screen-benefited cancer. Increasing the interval was more efficient regarding colonoscopies per cancer prevented.

Adoption of faecal immunochemical testing for 2-week-wait colorectal patients during the COVID-19 pandemic: an observational cohort study reporting a new service at a regional centre.

AIM: The COVID-19 pandemic has resulted in the near-complete loss of routine endoscopy services. We describe a major reorganization of service at a regional referral centre (Royal Surrey NHS Foundation Trust) to manage the crisis. Faecal immunochemical testing (FIT) was implemented for triage to make optimum use of limited diagnostic resources. Consultations were switched from face-to-face to telephone. Our aim was to evaluate the impact FIT had on resource allocation and patient diagnoses in the first 3 months of use. METHOD: All colorectal 2-week-wait patient referrals were posted a pack requesting FIT and notification of telephone consultation. A prepaid envelope was included for return of the samples. At consultation, FIT was incorporated with the presenting symptoms to guide the choice of investigation and triage urgency. FIT ≥10 µg/g was interpreted as positive. Outcome data were collected prospectively and compared with retrospective audit data from prepandemic levels across 3 months. RESULTS: From 26 March 2020 to 2 July 381 patients were referred who were invited to provide FIT samples and underwent telephone consultations. Three hundred and fifty eight FIT samples were returned (94%). Onward referral for colonoscopy reduced from 62% to 34% (P < 0.001). There were 14 colorectal cancers (CRC) (3.7%) diagnosed, which was not statistically different from the prepandemic level of 3.9% (P = 0.995). Twelve of the 14 patients with a CRC diagnosis had provided samples; all 12 had FIT ≥10 µg/g and were offered fast-track investigations. CONCLUSIONS: The incorporation of FIT optimized the allocation of limited resources to triage those who required urgent colonic investigation for detecting CRC.