The Effect of the Variability in Fecal Immunochemical Test Sample Collection Technique on Clinical Performance

Faecal haemoglobin concentration and colorectal cancer site, stage and grade in a symptomatic cohort

AIM

Minimal evidence exists regarding faecal immunochemical tests (FITs) for colorectal cancer (CRC) site, stage and grade in symptomatic patients. The primary aim is to determine any association between faecal haemoglobin concentration (f-Hb) (analysed with OC-Sensor™ Pledia) and these prognostic factors. The secondary aim is to determine the association between f-Hb and anaemia, microcytosis and iron deficiency (Hb, mean corpuscular volume [MCV] and ferritin).

METHODOLOGY

Symptomatic 2-week wait CRC patients with FIT were included (July 2019-October 2022). Median f-Hb and interquartile range according to sex, stage, grade and site (right-sided, caecum to transverse colon, R-CRC; left-sided, splenic flexure to rectum, L-CRC) were compared using the Mann-Whitney U test. Hb, MCV and ferritin were categorized into two groups and the median f-Hb was compared using the Mann-Whitney U test.

RESULTS

In all, 114 patients (57 women, 57 men) were studied; 46 had R-CRC (f-Hb = 113 μg Hb/g) and 68 had L-CRC (f-Hb = 342 μg Hb/g) (P = 0.07). Sixty-nine were moderately differentiated CRC (f-Hb = 183 μg Hb/g) and 29 were poorly differentiated (f-Hb = 866 μg Hb/g) (P = 0.04). By T-stage, 35 were early (T1/2) (f-Hb = 170 μg Hb/g) and 79 were advanced (T3/4) (f-Hb = 200 μg Hb/g) (P = 0.06). The relationship between f-Hb and Hb, MCV and ferritin was not significant. Poorly differentiated (P = 0.04) and later stage (P = 0.02) R-CRC had significantly lower f-Hb compared to L-CRC.

CONCLUSIONS

Right-sided CRC is associated with lower f-Hb than left. Poorly differentiated and later staged L-CRC had higher median f-Hb. These data add to existing evidence suggesting that FIT may be less sensitive for right-sided CRC. Strategies to mitigate the potential for missed or FIT-negative right-sided CRC are required.

The Diagnostic Performance of Fecal Immunochemical Tests for Detecting Advanced Neoplasia at Surveillance Colonoscopy

BACKGROUND & AIMS

An increasing burden on health care resources has resulted in a backlog of individuals requiring colonoscopy, with delays in surveillance possibly detrimental for individuals at increased risk of colorectal cancer (CRC). This study investigated the use of a 2-sample fecal immunochemical test (FIT) to establish those most likely to have advanced neoplasia (AN) and in need of prioritized surveillance colonoscopy.

METHODS

This was a prospective study conducted in the tertiary care setting. Participants completed a 2-sample FIT (OC-Sensor, Eiken Chemical Company) within 90 days of surveillance colonoscopy. The sensitivity of FIT for detection of AN (CRC or advanced adenoma) in moderate- and high-risk individuals was determined at fecal hemoglobin thresholds between 2 and 80 μg/g feces.

RESULTS

A total of 766 patients were included (median age, 66.1 years [interquartile range, 58.1-72.9]; 49.9% male), with AN detected in 8.6% (66/766, including 5 CRC). For moderate-risk individuals (with prior history of adenoma or a significant family history of CRC), sensitivity of FIT for AN ranged from 73.5% at 2 μg/g feces, to 10.2% at 80 μg/g feces. For high-risk conditions (confirmed/suspected genetic syndromes or prior CRC), sensitivity of FIT was similar, ranging from 70.6% at the lowest positivity threshold of 2 μg/g feces, to 11.8% at 80 μg/g feces. Independent variables in the whole cohort for association with detection of AN at surveillance colonoscopy were age (odds ratio, 1.03; 95% confidence interval, 1.00-1.06) and FIT hemoglobin result ≥10 μg/g feces (odds ratio, 1.81; 95% confidence interval, 1.04-3.16).

CONCLUSIONS

The use of FIT before surveillance colonoscopy provides clinicians with insights into the risk of AN. This raises the possibility of a method to triage individuals, facilitating the more efficient management of endoscopic resources.

Multiple Negative Fecal Immunochemical Tests Reduce Risk of Advanced Neoplasia in a Colonoscopy Surveillance Program

BACKGROUND & AIMS

In above-average-risk individuals undergoing colonoscopy-based surveillance for colorectal cancer (CRC), screening with fecal immunochemical tests (FIT) between colonoscopies might facilitate personalization of surveillance intervals. Because a negative FIT is associated with a reduced risk for CRC, we examined the relationship between number of rounds of negative FIT and risk for advanced neoplasia in individuals undergoing surveillance colonoscopy.

METHODS

We conducted a retrospective cohort study on 4021 surveillance intervals in 3369 individuals (50-74 years), who had completed a 2-sample FIT between colonoscopies, from 1 to 4 rounds at 1-2 yearly intervals, each with a negative result (<20 μg hemoglobin/g feces). Incidence of advanced neoplasia (CRC or advanced adenoma) was determined at the follow-up colonoscopy. Competing-risk regression was used to assess the association between multiple negative FIT results and the risk of advanced neoplasia within 2 years.

RESULTS

The incidence of advanced neoplasia in the cohort was 9.9% and decreased with increasing numbers of rounds of negative FIT results: 11.1% after 1 negative FIT to 5.7% after 4 negative FIT. The risk of advanced neoplasia was significantly lower in participants with 3 (subdistribution hazard ratio, 0.50; 95% confidence interval, 0.24-0.97) and 4 (subdistribution hazard ratio, 0.33; 95% confidence interval, 0.15-0.73) rounds of negative FIT compared with only 1 negative FIT.

CONCLUSIONS

There was a low risk of advanced neoplasia after multiple rounds of negative FIT in above-average-risk people undergoing surveillance with no neoplasia or nonadvanced adenoma at prior colonoscopy. This supports the use of interval FIT to personalize surveillance by lengthening colonoscopy intervals following multiple negative FIT results.

A True Positive and a False Negative? The Dilemma of Negative Colonoscopy After a Positive Fecal Occult Blood Test

INTRODUCTION

Many colonoscopies following a positive fecal immunochemical test (FIT) will not identify a probable cause for fecal blood, and missed neoplasia is a concern. The study determined whether the absence of neoplasia at a FIT positive diagnostic colonoscopy was due to a missed lesion and whether the initial FIT hemoglobin (f-Hb) concentration could predict missed lesions.

METHODS

This was a retrospective audit of patients who had undergone diagnostic colonoscopy after FIT screening (2 sample ≥ 20 µg Hb/g feces). Probable bleeding lesions including cancer, advanced adenoma, colitis, and angiodysplasia were considered a "positive colonoscopy outcome." For those with a negative outcome, findings at the subsequent colonoscopy were assessed.

RESULTS

There were 1087 good quality colonoscopies within 12 months of a positive FIT. In total, 171 (15.7%) patients had a positive outcome at the diagnostic colonoscopy. Subsequent colonoscopies of negative outcome cases (n = 418, median of 3.1y later) were reviewed; of these, there were 57 (13.6%) cases with a positive outcome. This included CRC in 0.5% (n = 2) and advanced adenoma in 11.7% (n = 49). High f-Hb and having both FIT samples ≥ 20 µg/g feces were associated with a positive outcome at the original diagnostic colonoscopy (p < 0.05). However, f-Hb was not predictive for a positive outcome at the subsequent colonoscopy by either maximum f-Hb (p = 0.768), total f-Hb (p = 0.459), or both FIT samples ≥ 20 µg/g (p = 0.091).

CONCLUSION

A small proportion of "false" positive FIT results had cancer or advanced adenoma found at the subsequent colonoscopy. A missed lesion could not be predicted by the initial FIT f-Hb.

Quality Improvement of Sample Collection Increases the Diagnostic Accuracy of Quantitative Fecal Immunochemical Test in Colorectal Cancer Screening: A Pilot Study

Objective: The diagnostic efficiency of the quantitative fecal immunochemical test (qFIT) has large variations in colorectal cancer (CRC) screening. We aimed to explore whether the practical sample collection operant training could improve the diagnostic accuracy of the qFIT in CRC screening.

Methods: Moderate-/high-risk individuals aged 50–75 years old were invited to participate in a prospective observational study between July 2020 and March 2021. Participants took a qFIT sample without fecal sample collection operant training in advance and then completed another qFIT sample after the operant training. The primary outcome was the sensitivity and specificity of the qFITs for CRC and advanced colorectal neoplasia (ACRN). The secondary outcome was the difference in the area under the curves (AUCs) and the concentrations of the fecal hemoglobin (Hb) between the qFIT without and after the operant training.

Results: Out of 913 patients, 81 (8.9%) patients had ACRN, including 25 (2.7%) patients with CRC. For CRC, the sensitivities of the qFIT without and after the operant training at 10 μg/g were 80.4 and 100.0%, respectively, and the specificities were 90.1 and 88.4%, respectively. For ACRN, the sensitivities were 49.4 and 69.1% and the specificities were 91.7 and 91.3%, respectively. The AUC of the qFIT after the operant training was significantly higher than that without the operant training for CRC (p = 0.027) and ACRN (p = 0.001). After the operant training, the concentration of the fecal Hb was significantly higher than that without the operant training (p = 0.009) for ACRN, but there was no significant difference for CRC (p = 0.367).

Conclusion: Practical sample collection operant training improves the diagnostic accuracy of the qFIT, which increases the detection of the low concentrations of fecal Hb. Improving the quality of the sample collection could contribute to the diagnostic efficiency of the qFIT in CRC screening.