Service evaluation of faecal immunochemical testing introduced for use in North East London for patients at low risk of colorectal cancer

Faecal Immunochemical Testing to Detect Colorectal Cancer in Symptomatic Patients: A Diagnostic Accuracy Study

(1) Background: NHS England recommended faecal immunochemical testing (FIT) for symptomatic patients in June 2020 to rationalise limited diagnostic services during COVID-19. (2) Aim: to investigate the diagnostic performance of FIT, analysing the proportion of FIT-negative colorectal cancers (CRC) missed in symptomatic patients and how this risk could be mitigated. (3) Design and Setting: a retrospective study of biochemistry and cancer databases involving patients referred from primary healthcare with suspected CRC to a single secondary care trust in North East London. (4) Methods: a retrospective cohort diagnostic accuracy study was undertaken to determine the performance of FIT for detecting CRC at 10 µgHb/g. (5) Results: between January and December 2020, 7653 patients provided a stool sample for FIT analysis; 1679 (22%) samples were excluded due to inadequate or incorrect specimens; 48% of suspected CRC referrals completed FIT before evaluation; 86 FIT tested patients were diagnosed with histologically proven CRC. At 10 µgHb/g, FIT performance was comparable with the existing literature with a sensitivity of 0.8140 (95% CI 0.7189-0.8821), a specificity of 0.7704 (95% CI 0.7595-0.7809), a positive predictive value (PPV) of 0.04923 (95% CI 0.03915-0.06174), a negative predictive value (NPV) of 0.9965 (95% CI 0.9943-0.9978), and a likelihood ratio (LR) of 3.545; 16 patients with CRC had an FIT of ≤10 µgHb/g (18.6% 95% CI 11.0-28.4%). (6) Conclusions: this study raises concerns about compliance with FIT testing and the incidence of FIT-negative CRC at the NICE recommended threshold and how this risk can be mitigated without colonic imaging. Whilst FIT may have facilitated prioritisation during COVID-19, we must be cautious about using FIT alone to determine which patients are referred to secondary care or receive further investigation.

Faecal immunochemical testing (FIT) in primary care: a follow-up service evaluation

AIM

Colorectal cancer (CRC) is the fourth most common cancer in the UK. Following National Institute for Health and Care Excellence guidance for faecal immunochemical testing (FIT), we introduced a service for the measurement of faecal haemoglobin (f-Hb) in symptomatic patients. Previously, we evaluated the first 6 months of the service in three local boroughs, here we re-examine the use of FIT, over a similar 6 months in the two successive years.

METHODS

Patients who had FIT requested in April-September 2020 and 2021 were studied. Results were obtained from the laboratory information systems and matched with the clinical outcomes of those referred via the urgent lower gastrointestinal cancer pathway. Patient demographics, reason for referral, clinical outcome and diagnostic test performance are reported.

RESULTS

In 2020, 4042 samples were analysed and 57 CRC detected. In 2021, 10 508 samples were analysed and 65 CRC detected. Six (4.9%) patients with CRC had f-Hb <10 µg/g, of whom three were anaemic. In 2020, 27.7% of samples were from patients under 50 years; and in 2021, 32.8%. Sensitivity, specificity, positive predictive value and negative predictive value of f-Hb at ≥10 µg/g for CRC were 92.9%, 46.6%, 6.4% and 99.4% in 2020 and 96.9%, 29.9%, 3.2% and 99.8% in 2021.

CONCLUSIONS

As currently used in primary care in North East London, specificity of FIT at a cut-off of 10 µg/g is much lower than in published studies and the impact of this on colorectal services needs to be considered.

Prevalence of repeat faecal immunochemical testing in symptomatic patients attending primary care

AIM

The faecal immunochemical test (FIT) for faecal haemoglobin (f-Hb) helps determine the risk of colorectal cancer (CRC) and has been integrated into symptomatic referral pathways. 'Safety netting' advice includes considering referral for persistent symptoms, but no published data exists on repeated FITs. We aimed to examine the prevalence of serial FITs in primary care and CRC risk in these patients.

METHOD

A multicentre, retrospective, observational study was conducted of patients with two or more consecutive f-Hb results within a year from three Scottish Health Boards which utilize FIT in primary care. Cancer registry data ensured identification of CRC cases.

RESULTS

Overall, 135 396 FIT results were reviewed, of which 12 359 were serial results reported within 12 months (9.1%), derived from 5761 patients. Of these, 42 (0.7%) were diagnosed with CRC. A total of 3487 (60.5%) patients had two f-Hb < 10 μg/g, 944 (16.4%) had f-Hb ≥ 10 μg/g followed by <10 μg/g, 704 (12.2%) f-Hb < 10 μg/g followed by ≥10 μg/g and 626 (10.9%) had two f-Hb ≥ 10 μg/g. The CRC rate in each group was 0.1%, 0.4%, 1.4% and 4.0%, respectively. Seven hundred and thirty four patients submitted more than two FITs within a year. The likelihood of one or more f-Hb ≥ 10 μg/g rose from 40.4% with two samples to 100% with six, while the CRC rate fell from 0.8% to 0%.

CONCLUSION

Serial FITs within a year account for 9.1% of all results in our Boards. CRC prevalence amongst symptomatic patients with serial FIT is lower than in single-FIT cohorts. Performing two FITs within a year for patients with persistent symptoms effectively acts as a safety net, while performing more than two within this timeframe is unlikely to be beneficial.

Faecal immunochemical testing (FIT) in patients with signs or symptoms of suspected colorectal cancer (CRC): a joint guideline from the Association of Coloproctology of Great Britain and Ireland (ACPGBI) and the British Society of Gastroenterology (BSG)

Faecal immunochemical testing (FIT) has a high sensitivity for the detection of colorectal cancer (CRC). In a symptomatic population FIT may identify those patients who require colorectal investigation with the highest priority. FIT offers considerable advantages over the use of symptoms alone, as an objective measure of risk with a vastly superior positive predictive value for CRC, while conversely identifying a truly low risk cohort of patients. The aim of this guideline was to provide a clear strategy for the use of FIT in the diagnostic pathway of people with signs or symptoms of a suspected diagnosis of CRC. The guideline was jointly developed by the Association of Coloproctology of Great Britain and Ireland/British Society of Gastroenterology, specifically by a 21-member multidisciplinary guideline development group (GDG). A systematic review of 13 535 publications was undertaken to develop 23 evidence and expert opinion-based recommendations for the triage of people with symptoms of a suspected CRC diagnosis in primary care. In order to achieve consensus among a broad group of key stakeholders, we completed an extended Delphi of the GDG, and also 61 other individuals across the UK and Ireland, including by members of the public, charities and primary and secondary care. Seventeen research recommendations were also prioritised to inform clinical management.

Faecal immunochemical tests safely enhance rational use of resources during the assessment of suspected symptomatic colorectal cancer in primary care: systematic review and meta-analysis

OBJECTIVE

Implementation of faecal immunochemical tests (FIT) as a triage test in primary healthcare may improve the efficiency of referrals without missing cases of colorectal cancer (CRC). We aim to summarise the performance characteristics of FITs for CRC in symptomatic patients presenting to primary healthcare.

DESIGN

We performed a systematic literature review of Medline and EMBASE databases from May 2018 to November 2020. Previous related systematic searches were also adapted to this aim and completed with reference screening. We identified studies performed on adult patients consulting for abdominal symptoms in primary care which reported data such that the FIT diagnostic performance parameters for CRC could be obtained. Bivariate models were used to synthesise available evidence. Meta-regression analysis was performed to evaluate the causes of heterogeneity.

RESULTS

Twenty-three studies (69 536 participants) were included (CRC prevalence 0.3%-6.2%). Six studies (n=34 691) assessed FIT as rule in test (threshold of ≥150 µg Hb/g faeces) showing a sensitivity of 64.1% (95% CI 57.8% to 69.9%) and a specificity of 95.0% (95% CI 91.2% to 97.2%). A threshold of 10 µg/g (15 studies; n=48 872) resulted in a sensitivity of 87.2% (95% CI 81.0% to 91.6%) and a specificity of 84.4% (95% CI 79.4% to 88.3%) for CRC. At a 20 µg Hb/g faeces threshold (five studies; n=24 187) less than one additional CRC would be missed per 1000 patients investigated compared with 10 µg Hb/g faeces threshold (CRC prevalence 2%).

CONCLUSION

FIT is the test of choice to evaluate patients with new-onset lower gastrointestinal symptoms in primary healthcare.

A cohort study of duplicate faecal immunochemical testing in patients at risk of colorectal cancer from North-West England

OBJECTIVES

We sought to investigate if duplicate faecal immunochemical testing (FIT) sampling improves the negative and positive predictive value of patients thought to be at risk of colorectal cancer (CRC). Specifically, we aimed to investigate whether the proportion of FIT-negative CRC missed by a single FIT test in symptomatic patients could be reduced by duplicate FIT testing.

DESIGN

A retrospective service evaluation cohort study of the diagnostic accuracy of duplicate FIT testing.

SETTING

Patients referred from primary care with suspected CRC to four secondary care trusts in North-West England.

PARTICIPANTS

28 622 patients over 18-years-old with lower gastrointestinal symptoms suggestive of CRC who completed two FIT samples.

PRIMARY AND SECONDARY OUTCOME MEASURES

The performance of duplicate FIT for detecting CRC at a threshold of 10 µgHb/g.

RESULTS

The sensitivity if either test was >10 µgHb/g was 0.978 (0.955-0.989), specificity was 0.662 (0.657-0.668), positive predictive value 0.031 (0.028-0.035) and negative predictive value 1.00 (0.999-1.00). Despite two-thirds of patients (18952) being negative following two tests, at this threshold only seven CRC were missed over a 26-month period. All seven patients had other high-risk features which should have prompted investigation.

CONCLUSIONS

This study suggests that in routine NHS practice, a duplicate FIT sample strategy together with clinical evaluation for evidence of anaemia and weight loss is superior to a single FIT sample alone and would allow symptomatic patients to be managed in primary care without the need for urgent referral to secondary care for urgent colonic imaging.

Alternative diagnoses and demographics associated with a raised quantitative faecal immunochemical test in symptomatic patients

Background

The faecal immunochemical test (FIT) has proven utility for colorectal cancer detection in symptomatic patients. However, most patients with a raised faecal haemoglobin (f-Hb) do not have colorectal cancer. We investigated alternative diagnoses and demographics associated with a raised f-Hb in symptomatic patients.

Methods

A retrospective, observational study was performed of patients with FIT submitted between August 2018 to January 2019 in NHS Greater Glasgow and Clyde followed by colonoscopy. Colonoscopy/pathology reports were searched for alternative diagnoses. Covariables were compared using the χ² test. Multivariate binary logistic regression identified independent predictors of a raised f-Hb.

Results

1272 patients were included. In addition to colorectal cancer (odds ratio (OR), 9.27 (95% confidence interval (CI): 3.61–23.83; p < 0.001)), older age (OR, 1.52 (95% CI: 1.00–2.32; p = 0.05)), deprivation (OR, 1.54 (95% CI: 1.21–1.94; p < 0.001)), oral anticoagulants (OR, 1.78 (95% CI: 1.01–3.15; p = 0.046)), rectal bleeding (OR, 1.47 (95% CI: 1.15–1.88; p = 0.002)), advanced adenoma (OR, 7.52 (95% CI: 3.90–14.49; p < 0.001)), non-advanced polyps (OR, 1.78 (95% CI: 1.33–2.38; p < 0.001)) and inflammatory bowel disease (IBD) (OR, 4.19 (95% CI: 2.17–8.07; p < 0.001)) independently predicted raised f-Hb. Deprivation (Scottish Index of Multiple Deprivation (SIMD) 1-2: OR, 2.13 (95% CI: 1.38–3.29; p = 0.001)) independently predicted a raised f-Hb in patients with no pathology found at colonoscopy.

Conclusions

An elevated f-Hb is independently associated with older age, deprivation, anticoagulants, rectal bleeding, advanced adenoma, non-advanced polyps and IBD in symptomatic patients. Deprivation is associated with a raised f-Hb in the absence of pathology. This must be considered when utilising FIT in symptomatic patients.

Combining the quantitative faecal immunochemical test and full blood count reliably rules out colorectal cancer in a symptomatic patient referral pathway

PURPOSE

Faecal Immunochemical Test (FIT) has proven utility for Colorectal Cancer (CRC) detection in symptomatic patients. Most studies have examined FIT in symptomatic patients subsequently referred from primary care. We investigated associations between CRC and FIT in both referred and non-referred symptomatic patients.

METHODS

A retrospective, observational study of all patients with a FIT submitted Aug 2018 to Jan 2019 in NHS GG&C was performed. Referral to colorectal/gastroenterology and decision to perform colonoscopy were recorded. FIT results were grouped as f-Hb < 10/10-149/150-399/ ≥ 400 μg/g. The MCN cancer registry identified new cases of CRC. Covariables were compared using the χ2 test. Multivariate binary logistic regression identified independent predictors of CRC.

RESULTS

A total of 4968 patients were included. Raised FIT correlated with decision to refer (p < 0.001) and scope (p < 0.001). With 23-month median follow-up, 61 patients were diagnosed with CRC. These patients were older (median 69 vs 59 years, cancer and no cancer respectively, p = 0.001), more likely to be male (55.7% vs 42.1%, p = 0.033), and to report rectal bleeding (51.7% vs 36.1%, p = 0.013). FIT (< 10 µg/g 8.2% vs 76.7% and ≥ 400 µg/g 55.7% vs 3.8%, p < 0.001) and anaemia (45.9% vs 19.7%, p < 0.001) were associated with CRC. On multivariate analysis, age (p = 0.023), male sex (p = 0.04), FIT (≥ 400 OR 54.256 (95% CI:20.683-142.325; p < 0.001)), and anaemia (OR 1.956 (1.071-3.574; p = 0.029)) independently predicted CRC. One patient (0.04%) with a negative FIT and normal haemoglobin had CRC.

CONCLUSION

GP referral and secondary care investigation patterns were influenced by FIT. The combination of normal Hb and f-Hb excluded CRC in 99.96% of cases, providing excellent reassurance to those prioritising access to endoscopy services.

Faecal calprotectin is not necessarily required as a screen for significant bowel disease in primary care

OBJECTIVE

NICE recommends measurement of faecal haemoglobin (f-Hb) using faecal immunochemical test (FIT) when colorectal cancer is suspected and calprotectin (f-Cal) in the context of inflammatory bowel disease, though neither is disease specific. During the COVID-19 pandemic, f-Hb has been a requirement prior to referral for endoscopy in England; f-Cal is often performed simultaneously. The aim of this study was to investigate test performance of both tests for significant bowel disease in those patients referred.

DESIGN

All adult patients with simultaneous measurements of f-Hb and f-Cal between April 2019 and September 2020 were included. For those referred, outcomes were determined from clinical records.

RESULTS

650 patients with simultaneous samples for f-Hb an f-Cal were managed in Primary Care; 319 patients were referred to hospital; SBD was found in 32 (10.0%) (CRC 5, high risk adenomas 5, IBD 22). At a cut-off of 10 μg/g for f-Hb and 200 μg/g for f-Cal, the sensitivity, specificity and negative predictive value for diagnosis of SBD were 84.4%, 58.2% and 96.7% and 68.8%, 89.6% and 95.7%, respectively. Performance of both tests would have enabled diagnosis of two more cases of significant, but non-malignant, bowel disease but required over 4% more referrals for investigation.

CONCLUSION

Use of FIT has become established to assist prioritisation of patients for referral from Primary Care. Whilst introduced specifically for CRC, FIT performs well as a rule out for IBD in Primary Care and the use of f-Cal is not required.

Faecal immunochemical test for patients with 'high-risk' bowel symptoms: a large prospective cohort study and updated literature review

Background

We evaluated whether faecal immunochemical testing (FIT) can rule out colorectal cancer (CRC) among patients presenting with ‘high-risk’ symptoms requiring definitive investigation.

Methods

Three thousand five hundred and ninety-six symptomatic patients referred to the standard urgent CRC pathway were recruited in a multi-centre observational study. They completed FIT in addition to standard investigations. CRC miss rate (percentage of CRC cases with low quantitative faecal haemoglobin [f-Hb] measurement) and specificity (percentage of patients without cancer with low f-Hb) were calculated. We also provided an updated literature review.

Results

Ninety patients had CRC. At f-Hb < 10 µg/g, the miss rate was 16.7% (specificity 80.1%). At f-Hb < 4 µg/g, the miss rate was 12.2% (specificity 73%), which became 3.3% if low FIT plus the absence of anaemia and abdominal pain were considered (specificity 51%). Within meta-analyses of 9 UK studies, the pooled miss rate was 7.2% (specificity 74%) for f-Hb < 4 µg/g.

Discussion

FIT alone as a triage tool would miss an estimated 1 in 8 cases in our study (1 in 14 from meta-analysis), while many people without CRC could avoid investigations. FIT can focus secondary care diagnostic capacity on patients most at risk of CRC, but more work on safety netting is required before incorporating FIT triage into the urgent diagnostic pathway.

Use of ColonFlag score for prioritisation of endoscopy in colorectal cancer

OBJECTIVE

Colorectal cancer (CRC) is the fourth most common cancer in UK. Symptomatic patients are referred via an urgent pathway and although most are investigated with colonoscopy <4% are diagnosed with cancer. There is therefore a need for a suitable triage tool to prioritise investigations. This study retrospectively examined performance of various triage tools in patients awaiting investigation on the urgent lower gastrointestinal cancer pathway DESIGN: All patients over 40 years of age on the urgent pathway awaiting investigation for suspected CRC on 1 May were included. After 6 months, outcomes were evaluated and the performance of the faecal immunochemical test (FIT), faecal haemoglobin concentration, age and sex test (FAST) and the artificial intelligence algorithm ColonFlag were examined.

RESULTS

532 completed investigations and received a diagnosis; 15 had CRC. 388 had a valid FIT result, of whom 11 had CRC; FAST Score ≥4.5 had sensitivity of 72.7%, specificity of 80.6% and would have failed to detect three tumours. Faecal haemoglobin (f-Hb) at cut-off of 10 µg/g and ColonFlag had equal sensitivity of 81.82%, ColonFlag had greater specificity 73.47%, compared with 64.99%. Both tests would have failed to detect two tumours but not in the same patients; when used in combination, sensitivity and specificity were 100% and 49.4%. When ColonFlag was applied to the cohort of 532, an additional four tumours would have been detected in patients without a valid FIT.

CONCLUSION

This study showed ColonFlag to have equal sensitivity and greater specificity than f-Hb at a cut-off of 10 µg/g as a triage tool for CRC.

Faecal haemoglobin concentration thresholds for reassurance and urgent investigation for colorectal cancer based on a faecal immunochemical test in symptomatic patients in primary care

Background

Faecal haemoglobin concentration (f-Hb), estimated using a faecal immunochemical test, can be safely implemented in primary care to assess risk of colorectal cancer (CRC). Clinical outcomes of patients presenting with symptoms of lower gastrointestinal disease were examined using an extensive range of f-Hb thresholds to decide on reassurance or referral for further investigation.

Methods

All patients who attended primary care and submitted a single faecal specimen faecal immunochemical test in the first year of the routine service had f-Hb estimated using HM-JACKarc: f-Hb thresholds from <2 to ≥ 400 µg Hb/g faeces (µg/g) were examined.

Results

Low f-Hb thresholds of <2, <7, <10 and <20 µg/g gave respective CRC risks of 0.1, 0.3, 0.3 and 0.4%, numbers needed to scope for one CRC of 871, 335, 300 and 249, and ‘false negative’ rates of 2.9, 11.4, 13.3 and 17.1%. With thresholds of <2, <7, <10 and <20 µg/g, 48.6, 74.6, 78.1 and 83.2% respectively of symptomatic patients could be managed without further investigation. With reassurance thresholds of <2 µg/g, <7 µg/g and <10 µg/g, the thresholds for referral for urgent investigation would be >400 µg/g, ≥200 µg/g and ≥100 µg/g. However, patients with a f-Hb concentration of <10 or <20 µg/g with iron deficiency anaemia, or with severe or persistent symptoms, should not be denied further investigation.

Conclusions

In primary care, f-Hb, in conjunction with clinical assessment, can safely and objectively determine individual risk of CRC and decide on simple reassurance or urgent, or routine referral.