Risk of missing colorectal cancer with a COVID-adapted diagnostic pathway using quantitative faecal immunochemical testing.

Y Maeda,D Weller,F V N Din,E Gray,P S Hall,M G Dunlop,J D Figueroa

doi:10.1093/bjsopen/zrab056

Abstract

BackgroundCOVID-19 has brought an unprecedented challenge to healthcare services. The authors’ COVID-adapted pathway for suspected bowel cancer combines two quantitative faecal immunochemical tests (qFITs) with a standard CT scan with oral preparation (CT mini-prep). The aim of this study was to estimate the degree of risk mitigation and residual risk of undiagnosed colorectal cancer.MethodDecision-tree models were developed using a combination of data from the COVID-adapted pathway (April–May 2020), a local audit of qFIT for symptomatic patients performed since 2018, relevant data (prevalence of colorectal cancer and sensitivity and specificity of diagnostic tools) obtained from literature and a local cancer data set, and expert opinion for any missing data. The considered diagnostic scenarios included: single qFIT; two qFITs; single qFIT and CT mini-prep; two qFITs and CT mini-prep (enriched pathway). These were compared to the standard diagnostic pathway (colonoscopy or CT virtual colonoscopy (CTVC)).ResultsThe COVID-adapted pathway included 422 patients, whereas the audit of qFIT included more than 5000 patients. The risk of missing a colorectal cancer, if present, was estimated as high as 20.2 per cent with use of a single qFIT as a triage test. Using both a second qFIT and a CT mini-prep as add-on tests reduced the risk of missed cancer to 6.49 per cent. The trade-off was an increased rate of colonoscopy or CTVC, from 287 for a single qFIT to 418 for the double qFIT and CT mini-prep combination, per 1000 patients.ConclusionTriage using qFIT alone could lead to a high rate of missed cancers. This may be reduced using CT mini-prep as an add-on test for triage to colonoscopy or CTVC.

Highlights

COVID-19 has brought unprecedented challenges to health and social services
This paper aimed to develop models to calculate the degree of risk mitigation and estimate residual risk of colorectal cancer (CRC) of the COVIDadapted pathway, considering selected alternative patterns of diagnostic pathways, and comparing them against the pre-COVID conventional diagnostic pathway
There would be a slight decrease in the rate of colonoscopies or CTVCs to 335 and 400 per 1000 for options 2 and 4 respectively. This COVID-adapted pathway is an example of adding a triage test sequence to an existing definitive diagnostic test[26]

Summary

Introduction

COVID-19 has brought unprecedented challenges to health and social services. The standard diagnostic pathway for suspected colorectal cancer (CRC) was severely curtailed at the onset of the pandemic with the majority of hospitals missing cancer targets[1]. The authors’ COVID-adapted pathway for suspected bowel cancer combines two quantitative faecal immunochemical tests (qFITs) with a standard CT scan with oral preparation (CT mini-prep). The risk of missing a colorectal cancer, if present, was estimated as high as 20.2 per cent with use of a single qFIT as a triage test. Using both a second qFIT and a CT mini-prep as add-on tests reduced the risk of missed cancer to 6.49 per cent. Conclusion: Triage using qFIT alone could lead to a high rate of missed cancers

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