Diagnostic accuracy of a quantitative faecal immunochemical test vs. symptoms suspected for colorectal cancer in patients referred for colonoscopy

Abstract

Objective: Determine diagnostic accuracy of a quantitative faecal immunochemical haemoglobin test (QuikRead go V R FIT, Orion Diagnostica Oy) in symptomatic patients referred for colonoscopy, at various cutoffs and for one or two tests. Methods: Patients referred to four endoscopy units in mid-Sweden between 2013 and 2017 provided information on lower abdominal symptoms and faecal samples from two separate days prior to colonoscopy. Results: In all, 5.4% (13/242) patients had colorectal cancer (CRC). For one FIT at cutoff 10 mg Hb/g faeces, sensitivity for CRC was 92% (95% CI 78-100%) and specificity 77% (95% CI 72-83%); equal to 74%; 95% CI 68-80 (178/242) colonoscopies potentially avoidable and one CRC missed. Based on the maximal outcome of two FITs, sensitivity was 100%, specificity 71% (66-77%) and 68%; 95% CI 62-74 (160/237) colonoscopies potentially avoidable. Among 17% (42/242) patients with one FIT of >200 mg Hb/g faeces, 85% (11/13) had CRC. Positive predictive values of FIT varied 16.9-26.2% depending on cutoff and one or two FITs, whereas NPVs were 99% and above in all scenarios. In 60 patients reporting rectal bleeding, one FIT at cutoff 10 mg Hb/g discriminated well between CRC and other conditions (p ¼ .001). In regression models, FIT was more important than age, sex and all symptoms. Conclusion: One or two FITs in symptomatic patients referred for colonoscopy imply powerful risk stratification abilities for CRC, even among patients reporting rectal bleeding. Larger studies in various settings will clarify how to make the best use of this opportunity.

Qualitative faecal immunochemical tests (FITs) for diagnosing colorectal cancer in patients with histories of rectal bleeding in primary care: a cohort study

“…It is also possible that the presence of rectal bleeding was recorded to a greater extent than the absence of bleeding. On the other hand, in four studies on patients referred to secondary care with the same magnitude of CRC diagnoses as in this study (3.0-5.4%), and where a history of rectal bleeding was registered, the prevalence of rectal bleeding was 24.8-36.0% which is similar to the 29.9% in this study [23,24,26,27]. Another aspect is that only patients for whom FITs were requested and subsequently provided were included in the study, and it is probable that an unknown number of patients with rectal bleeding were referred without providing FITs.…”

“…To our knowledge, this is the first study in primary care that evaluates FIT results for patients with a history of rectal bleeding. In a recently published Swedish study, 60 patients referred for colonoscopy had a history of rectal bleeding, and a FIT with a cutoff of > 10 μg Hb/g faeces showed 100% sensitivity, 74.1% specificity, 30.0% PPV and 100% NPV for CRC for these patients [27]. A Scottish study evaluating the accuracy of a quantitative FIT and faecal calprotectin in patients referred for investigation of bowel symptoms, and in which 33.9% of the patients had a documented history of rectal bleeding, showed a 4.3% PPV of rectal bleeding for CRC which is similar to the present study [24].…”

“…Evidence is growing that FITs are useful as diagnostic tests in primary care before decisions are taken on the referral of symptomatic patients [18][19][20][21]. Studies on patients already referred to secondary care have included those with a history of rectal bleeding [22][23][24][25][26][27]. To our knowledge, no study in primary care has compared FIT results for patients presenting with and without rectal bleeding, respectively.…”

Quantitative faecal immunochemical test for patients with high risk bowel symptoms: a prospective cohort study

“…37 Only a single stool sample was requested from each patient, and Hogberg et al (2017) indicate that this could lead to missing one tenth of symptomatic CRCs and adenomas with high grade dysplasia 38 , compared to using three samples; while other studies did not find any significant improvement in test accuracy when two FITs were performed. 21,39 A final clinical diagnosis could not be obtained from records on all patients during the study period. As a consequence, several patients with a valid FIT result were excluded from the final analysis.…”

“…Employing FIT as a triage tool can target potentially unpleasant and harmful investigations for patients who would most benefit; f-Hb thresholds of ≥10 μg/g and ≥4 μg/g, could potentially allow 80% and 73% patients to avoid further investigations, respectively, which is similar to previous findings. 24,39 However, the missed CRC rate is too high using FIT on its own, but can be minimised by referring patients with anaemia or abdominal pain despite having a low FIT result, thus ensuring safety netting using these clinical features. This approach could result in only 44% of symptomatic patients without cancer being investigated further (using our findings).…”