The use of faecal immunochemical testing in the decision-making process for the endoscopic investigation of iron deficiency anaemia

Faecal immunochemical tests can improve colonoscopy triage in patients with iron deficiency: A systematic review and meta-analysis

BACKGROUND

Use of the faecal immunochemical test (FIT) to triage patients with iron deficiency (ID) for colonoscopy due to suspected colorectal cancer (CRC) may improve distribution of colonoscopic resources. We reviewed the diagnostic performance of FIT for detecting advanced colorectal neoplasia, including CRC and advanced pre-cancerous neoplasia (APCN), in patients with ID, with or without anaemia.

METHODS

We performed a systematic review of three databases for studies comprising of patients with ID, with or without anaemia, completing a quantitative FIT within six months prior to colonoscopy, where test performance was compared against the reference standard colonoscopy. Random effects meta-analyses determined the diagnostic performance of FIT for advanced colorectal neoplasia.

RESULTS

Nine studies were included on a total of n=1761 patients with ID, reporting FIT positivity thresholds between 4-150 µg haemoglobin/g faeces. Only one study included a non-anaemic ID (NAID) cohort. FIT detected CRC and APCN in ID patients with 90.7 % and 49.3 % sensitivity, and 81.0 % and 82.4 % specificity, respectively. FIT was 88.0 % sensitive and 83.4 % specific for CRC in patients with ID anaemia at a FIT positivity threshold of 10 µg haemoglobin/g faeces.

CONCLUSIONS

FIT shows high sensitivity for advanced colorectal neoplasia and may be used to triage those with ID anaemia where colonoscopic resources are limited, enabling those at higher risk of CRC to be prioritised for colonoscopy. There is a need for further research investigating the diagnostic performance of FIT in NAID patients.

Development and validation of a faecal immunochemical test-based model in the work-up of patients with iron deficiency anaemia

Objective

In patients with iron deficiency anaemia (IDA), the diagnostic yield of gastroscopy and colonoscopy (bidirectional endoscopy) in detecting neoplastic lesions is low. This study aimed to develop and validate a faecal immunochemical test (FIT)-based model to optimise the work-up of patients with IDA.

Methods

Outpatients with IDA were enrolled in a prospective, multicentre study from April 2016 to October 2019. One FIT was performed before bidirectional endoscopy. Significant gastrointestinal lesions were recorded and a combined model developed with variables that were independently associated with significant colorectal lesions in the multivariate analysis. The model cut-off was selected to provide a sensitivity of at least 95% for colorectal cancer (CRC) detection, and its performance was compared to different FIT cut-offs. The data set was randomly split into two groups (developed and validation cohorts). An online calculator was developed for clinical application.

Results

The development and validation cohorts included 373 and 160 patients, respectively. The developed model included FIT value, age, and sex. In the development and validation cohorts, a model cut-off of 0.1375 provided a negative predictive value of 98.1 and 96.7% for CRC and 90.7 and 88.3% for significant colorectal lesions, respectively. This combined model reduced the rate of missed significant colorectal lesions compared to FIT alone and could have avoided more than one-fourth of colonoscopies.

Conclusion

The FIT-based combined model developed in this study may serve as a useful diagnostic tool to triage IDA patients for early endoscopic referral, resulting in considerable reduction of unnecessary colonoscopies.

The Value of Quantitative Faecal Immunochemical Testing as a Prioritisation Tool for the Endoscopic Investigation of Patients With Iron Deficiency

Difficulty in providing endoscopy for patients with iron deficiency anaemia (IDA) during the COVID-19 pandemic has highlighted the requirement for a prioritisation tool. We aimed to test the validity of qFIT as a prioritisation tool in patients with iron deficiency and its ability to identify patients with advanced neoplastic lesions (ANLs). Data collected from patients referred with biochemically proven iron deficiency (ferritin ≤ 15 μg/L) and synchronous qFIT who underwent full gastrointestinal investigation within NHS Greater Glasgow and Clyde was analysed retrospectively. Patients who did not undergo full investigation, defined as gastroscopy and colonoscopy or CT colonography, were excluded. ANLs were defined as defined as upper GI cancer, colorectal adenoma ≥ 1 cm or colorectal cancer. Area under the curve (AUC) analysis was performed on qFIT results and outcome, defined as the presence of an ANL. AUC analysis guided cut-off scores for qFIT. Patients with a qFIT of <10, 10–200, >200, were allocated a score of 1, 2, and 3, respectively. A total of 575 patients met criteria for inclusion into the study. Overall, qFIT results strongly predicted the presence of ANLs (AUC 0.87, CI 0.81–0.92; P < 0.001). The prevalence of ANLs in patients with scores 1–3 was 1.2, 13.5, and 38.9% respectfully. When controlled for other significant variables, patients with a higher qFIT score were statistically more likely to have an ANL (qFIT score = 2; OR 12.8; P < 0.001, qFIT score = 3, OR 50.0; P < 0.001). A negative qFIT had a high NPV for the presence of ANLs (98.8%, CI 97.0–99.5%). These results strongly suggest that qFIT has validity as a prioritisation tool in patients with iron deficiency; both allowing for a more informed decision of investigation of patients with very low risk of malignancy, and in identifying higher risk patients who may benefit from more urgent endoscopy.