Evaluation of new occult blood tests for detection of colorectal neoplasia

Detection of advanced colorectal neoplasia and relative colonoscopy workloads using quantitative faecal immunochemical tests: an observational study exploring the effects of simultaneous adjustment of both sample number and test positivity threshold

OBJECTIVE

When screening for colorectal cancer (CRC) using quantitative faecal immunochemical tests (FIT), test parameters requiring consideration are the faecal haemoglobin concentration (f-Hb) positivity cut-off and the number of stools sampled. This observational study explored variation in f-Hb between samples and the relationship between sensitivity for advanced neoplasia (AN, cancer or advanced adenoma) and colonoscopy workload across a range of independently-adjusted parameter combinations.

DESIGN

Quantitative FIT data (OC-Sensor) were accessed from individuals undergoing personalised colonoscopic screening with an offer of 2-sample FIT in the intervening years. We estimated variation in f-Hb between samples in 12 710 completing 2-sample FIT, plus test positivity rates (colonoscopy workload) and sensitivity for AN according to parameter combinations in 4037 instances where FIT was done in the year preceding colonoscopy.

RESULTS

There was large within-subject variability between samples, with the ratio for the second to the first sample f-Hb ranging up to 18-fold for all cases, and up to 56-fold for AN cases. Sensitivity for AN was greatest at lower f-Hb cut-offs and/or using 2-sample FIT. Colonoscopy workload varied according to how parameters were combined. Using different cut-offs for 1-sample FIT and 2-sample FIT to return similar sensitivity, workload was less with 2-sample FIT when the sensitivity goal exceeded 35%.

CONCLUSION

Variation in f-Hb between samples is such that both parameters are crucial determinants of sensitivity and workload; independent adjustment of each should be considered. The 2-sample FIT approach is best for detecting advanced adenomas as well as CRC provided that the colonoscopy workload is feasible.

Classifying interval cancers as false negatives or newly occurring in fecal immunochemical testing

OBJECTIVE

To classify interval colorectal cancers as false negatives or newly occurring cases in a biennial Fecal immunochemical test (FIT) screening program and by various interscreening intervals.

SETTING

Data from the Taiwanese biennial colorectal cancer screening program involving FIT from 2004 to 2014 were used to estimate the incidence rate of asymptomatic colorectal cancer and the rate of its subsequent progression to clinical mode.

METHODS

The sensitivity of detecting asymptomatic colorectal cancers excluding newly developed colorectal cancers was compared to the conventional estimate of sensitivity, the complementary FIT interval cancer rate as a percentage of the expected incidence rate ((1-I/E)%). The relative contribution of newly developed or false-negative cases to FIT interval colorectal cancers was estimated by age and interscreening intervals.

RESULTS

The Taiwanese biennial fecal immunochemical test screening program had a conventional sensitivity estimate of 70.2%. After newly developed colorectal cancers were separated from FIT interval cancers, the ability to detect asymptomatic colorectal cancers increased to 75.5%. FIT interval colorectal cancers from the biennial program mainly resulted from newly developed colorectal cancers (68.8%). The corresponding figures decreased to 61.1% for the annual program but increased to 74.7% for the triennial program. The preponderance of newly developed colorectal cancers among FIT interval cancers was more prominent in screenees aged 50-59  than in those aged 60-69.

CONCLUSIONS

Newly developed colorectal cancers showed a predominance among the FIT interval colorectal cancers in particular in the younger population screened. It is desirable to identify high-risk individuals to offer them a short interscreening interval or advanced detection methods to reduce their odds of developing interval cancer.

An evaluation of the SENTiFIT 270 analyser for quantitation of faecal haemoglobin in the investigation of patients with suspected colorectal cancer

BACKGROUND

An evaluation of SENTiFIT® 270 (Sentinel Diagnostics, Italy; Sysmex, Spain) analyser for the quantitation of faecal haemoglobin (f-Hb) was performed.

METHODS

The analytical imprecision, linearity, carry over and f-Hb stability were determined. Evaluation of the diagnostic accuracy was performed on 487 patients.

RESULTS

Within-run and between-run imprecision ranged 1.7%-5.1% and 3.8%-6.2%, respectively. Linearity studies revealed a mean recovery of 101.1% (standard deviation, 6.7%) for all dilutions. No carry over was detected below 7650 μg Hb/g faeces. Decay of f-Hb in refrigerated samples ranged 0.2%-0.5% per day. f-Hb in patients with advanced colorectal neoplasia (ACRN) (colorectal cancer [CRC] plus advanced adenoma [AA]) were significantly higher than from those with a normal colonoscopy. Sensitivity for ACRN at f-Hb cutoffs from 10 to 60 μg Hb/g faeces ranged from 28.9% (95% confidence interval [CI], 21.7%-37.2%) to 46.5% (95% CI, 38.1%-55%), the specificity ranged from 85% (95% CI, 82.3%-87.3%) to 93.2% (95% CI, 91.2%-94.8%), positive predictive values for detecting CRC and AA ranged from 11.6% (95% CI, 7.6%-17.2%) to 20.6% (95% CI, 13.3%-30.3%) and from 34.7% (95% CI, 28.1%-42%) to 42.3% (95% CI, 32.4%-52.7%), respectively, and the negative predictive value for ACRN ranged from 90.2% (95% CI, 87.9%-92.2%) to 88.4% (95% CI, 86%-90.4%). Using two samples per patient sensitivity increased with a slight decrease in specificity.

CONCLUSIONS

The analytical and clinical performances of SENTiFIT assay demonstrate a specific and accurate test for detecting ACRN in symptomatic patients and those undergoing surveillance.

Gastrointestinal Lesions in African American Patients With Iron Deficiency Anemia

Background:

Iron deficiency anemia (IDA) is a frequent disorder that is associated with many serious diseases. However, the findings of an evaluation of IDA-associated gastrointestinal disorders are lacking among African American patients.

Aim:

To determine the most prevalent gastrointestinal lesions among African American patients with IDA especially in young men.

Methods:

We reviewed medical records (n = 422) of patients referred for evaluation of IDA from 2008 to 2012. Iron deficiency anemia was diagnosed using clinical laboratory tests. The results of esophagogastroduodenoscopy, colonoscopy, and pathology specimens along with demographic data were abstracted and analyzed using Stata.

Results:

The mean age was 61.9 years, and 50.5% were women. In total, 189 patients (45%) had gross gastrointestinal (GI) bleeding. The most frequent diagnoses were gastritis (40%), benign colonic lesions (13%), esophagitis (9%), gastric ulcer (6%), and duodenitis (6%). GI bleeding was significantly more frequent in men (P = 0.001). Benign and malignant colonic lesions were significantly more present among older patients: 16% vs 6% (P = .005) and 5% vs 0% (P = .008), respectively. Colitis was more prevalent in younger patients (⩽50): 11% vs 2% (P = .001). In patients with gross lower GI bleeding, the top diagnoses were gastritis (25%), benign colon tumors (10%), and duodenitis (6%). Colon cancer was diagnosed among 15 patients, and all these patients were older than 50 years of age.

Conclusions:

Gastritis and colonic lesions are most common associated lesions with IDA among African Americans. So bidirectional endoscopy is required for unrevealing of the cause of IDA in asymptomatic patients.

A Randomised Trial of the Impact of New Faecal Haemoglobin Test Technologies on Population Participation in Screening for Colorectal Cancer

OBJECTIVES

To investigate the effect on participation in colorectal cancer screening of testing for blood products in faeces using technologies that remove dietary restrictions (i.e. immunochemical tests) and simplify faecal sampling (i.e. tests that use brush sampling).

METHODS

SETTING

Urban residents (n=1818) of Adelaide, Australia, aged between 50 and 69 years, randomly selected from the electoral roll.

DESIGN

Three randomised cohorts of 606 invitees were offered a screening test by mail in 2001. The Hemoccult SENSA and FlexSure OBT cohorts were instructed to sample three stools using a spatula while the InSureTM cohort sampled two stools using a brush. The Hemoccult SENSA cohort was asked to restrict certain (high-peroxidase) foods and drugs.

MAIN OUTCOME MEASURES

Participation (i.e. return of completed sample kits within 12 weeks) and generalised linear modelling (GLM) of relationships between participation, test technologies and demographic variables.

RESULTS

Participation was 23.4%, 30.5% and 39.6% for the Hemoccult, FlexSure and InSure cohorts, respectively (chi(2)=37.1, p<0.00001). GLM demonstrated that participation was increased by 28% by removal of restrictions (p=0.01) and by 30% by simplification of sampling (p=0.001); both together increased participation by 66% (p<0.001). The differences in participation between tests occurred in the first three weeks. Socio-economic status, gender or age did not significantly influence technology-based improvements in participation.

CONCLUSIONS

The brush-sampling faecal immunochemical test for haemoglobin (InSure) achieves the best participation rates by simplifying sampling and removing the need for restrictions of diet and drugs. Because participation in screening is vital to detection, this new technology should contribute to better detection of neoplasia at the population level.

Prescreening Evaluation of a Brush-Based Faecal Immunochemical Test for Haemoglobin

OBJECTIVES

To undertake a prescreening evaluation of a new brush-based faecal immunochemical test for haemoglobin, relative to a traditional spatula-sampling immunochemical test.

METHODS

SETTING

Patients aged between 24 and 90 years, scheduled to undergo diagnostic colonoscopy in two major urban hospitals, for a range of clinical indications.

DESIGN

Patients sampled three stools using a spatula for the reference FlexSure OBT test and two stools using a brush for the InSure test; order of sampling was randomised. Faecal haemoglobin was quantified by a modified InSure in a subset of patients to determine whether brush-sampling allowed discrimination between groups.

MAIN OUTCOME MEASURES

Sensitivity for cancer or adenoma; false-positive rate in normals. Faecal haemoglobin levels. Preference for sampling method.

RESULTS

InSure and FlexSure OBT did not differ in their sensitivities for cancer (27/36, 75% vs 29/36, 80.5%, respectively), adenomas >or= 10 mm (12/29, 41.4% vs 13/29, 44.8%) or adenomas <10 mm (each 8/56, 14.3%). Likewise, false-positive rates in normals were similar: 4/179 (2.2%) and 5/179 (2.8%) respectively (specificities of 97.8% and 97.2%, respectively). Levels of faecal haemoglobin were highest in those with cancers; those with adenomas had intermediate levels which were also significantly higher than those in normals. The brush sampling method was preferred by 38/46 (82.6%), while 4/46 (8.7%) preferred the spatula (p<0.00001).

CONCLUSIONS

InSure is as sensitive and specific as FlexSure OBT for faecal haemoglobin. The novel stool-sampling method of InSure allows discrimination between normals and classes of neoplasia, and is highly preferred. The brush-sampling faecal immunochemical test InSure should now be evaluated in a screening population.

Recommendations for a step-wise comparative approach to the evaluation of new screening tests for colorectal cancer

BACKGROUND

New screening tests for colorectal cancer continue to emerge, but the evidence needed to justify their adoption in screening programs remains uncertain.

METHODS

A review of the literature and a consensus approach by experts was undertaken to provide practical guidance on how to compare new screening tests with proven screening tests.

RESULTS

Findings and recommendations from the review included the following: Adoption of a new screening test requires evidence of effectiveness relative to a proven comparator test. Clinical accuracy supported by programmatic population evaluation in the screening context on an intention-to-screen basis, including acceptability, is essential. Cancer-specific mortality is not essential as an endpoint provided that the mortality benefit of the comparator has been demonstrated and that the biologic basis of detection is similar. Effectiveness of the guaiac-based fecal occult blood test provides the minimum standard to be achieved by a new test. A 4-phase evaluation is recommended. An initial retrospective evaluation in cancer cases and controls (Phase 1) is followed by a prospective evaluation of performance across the continuum of neoplastic lesions (Phase 2). Phase 3 follows the demonstration of adequate accuracy in these 2 prescreening phases and addresses programmatic outcomes at 1 screening round on an intention-to-screen basis. Phase 4 involves more comprehensive evaluation of ongoing screening over multiple rounds. Key information is provided from the following parameters: the test positivity rate in a screening population, the true-positive and false-positive rates, and the number needed to colonoscope to detect a target lesion.

CONCLUSIONS

New screening tests can be evaluated efficiently by this stepwise comparative approach.

Systematic review and bivariate/HSROC random-effect meta-analysis of immunochemical and guaiac-based fecal occult blood tests for colorectal cancer screening

BACKGROUND

Current literature evidences higher accuracy of immunological (iFOBT) vis-à-vis guaiac-based (gFOBT) fecal occult blood tests for colorectal cancer (CRC) screening. Few well-designed head-to-head comparisons exist.

AIM

This meta-analysis assesses the performances of two iFOBTs compared with an established gFOBT using colonoscopy as the gold standard.

METHODS

We mobilized a bivariate and a hierarchical summary receiver operating characteristic (HSROC) model. Positive likelihood ratio (LR) and negative likelihood ratio (LR) and diagnostic odds ratios were back-calculated. We constructed bivariate credibility ellipses in the HSROC space and calculated areas under the curve to obtain a global measure of test performance. Estimates are presented at 95% credibility levels.

RESULTS

We included and analyzed 21 studies. OC-Sensor was the best test for CRC screening, with high sensitivity (0.87; 95% credibility interval: 0.73-0.95) and specificity (0.93; 95% credibility interval: 0.84-0.96), optimal LR (12.01) and LR (0.14), and a high diagnostic odds ratio (88.05). Bivariate credibility ellipses showed OC-Sensor's dominance over Hemoccult (sensitivity: 0.47; 95% credibility interval: 0.37-0.58; specificity: 0.93; 95% credibility interval: 0.91-0.95).

CONCLUSION

Our findings support the use of OC-Sensor for CRC detection. The diagnostic estimates obtained may be extended to derive model parameters for economic decision models and to offer insight for future clinical and public health decision making. Our findings could influence the future of FOBTs within the CRC screening arsenal.

Population screening for colorectal cancer means getting FIT: the past, present, and future of colorectal cancer screening using the fecal immunochemical test for hemoglobin (FIT)

Fecal immunochemical tests for hemoglobin (FIT) are changing the manner in which colorectal cancer (CRC) is screened. Although these tests are being performed worldwide, why is this test different from its predecessors? What evidence supports its adoption? How can this evidence best be used? This review addresses these questions and provides an understanding of FIT theory and practices to expedite international efforts to implement the use of FIT in CRC screening.

Colorectal cancer screening in an equal access healthcare system

INTRODUCTION

The military health system (MHS) a unique setting to analyze implementation programs as well as outcomes for colorectal cancer (CRC). Here we look at the efficacy of different CRC screening methods, attributes and results within the MHS, and current barriers to increase compliance.

MATERIALS AND METHODS

A literature search was conducted utilizing PubMed and the Cochrane library. Key-word combinations included colorectal cancer screening, racial disparity, risk factors, colorectal cancer, screening modalities, and randomized control trials. Directed searches were also performed of embedded references.

RESULTS

Despite screening guidelines from several national organizations, extensive barriers to widespread screening remain, especially for minority populations. These barriers are diverse, ranging from education and access problems to personal beliefs. Screening rates in MHS have been reported to be generally higher at 71% compared to national averages of 50-65%.

CONCLUSION

CRC screening can be highly effective at improving detection of both pre-malignant and early cancers. Improved patient education and directed efforts are needed to improve CRC screening both nationally and within the MHS.

Fecal immunochemical tests compared with guaiac fecal occult blood tests for population-based colorectal cancer screening

Colorectal cancer (CRC) is the second most common cause of cancer deaths in Canadian men and women - accounting for almost 12% of all cancer deaths. In Ontario, it is estimated that 8100 persons were diagnosed with CRC in 2011, and 3250 died from the disease. CRC incidence and mortality rates in Ontario are among the highest in the world. Screening offers the best opportunity to reduce this burden of disease. The present report describes the findings and recommendations of Cancer Care Ontario's Fecal Immunochemical Tests (FIT) Guidelines Expert Panel, which was convened in September 2010 by the Program in Evidence-Based Care. The purpose of the present guideline is to evaluate the existing evidence concerning FIT to inform the decision on how to replace the current guaiac fecal occult blood test with FIT in the Ontario ColonCancerCheck Program. Eleven articles were included in the present guideline, comprising two systematic reviews, five articles reporting on three randomized controlled trials, and reports of four other studies. Additionally, one laboratory study was obtained that reported on several parameters of FIT tests that helped to inform the present recommendation. The performance of FIT is superior to the standard guaiac fecal occult blood test in terms of screening participation rates and the detection of CRC and advanced adenoma. Given greater specimen instability with the use of FIT, a pilot study should be undertaken to determine how to implement the FIT in Ontario.

Detection of methylated tissue factor pathway inhibitor 2 and human long DNA in fecal samples of patients with colorectal cancer in China

BACKGROUND

To investigate the feasibility of detecting methylated tissue factor pathway inhibitor (TFPI2) and quantifying human long DNA with fluorescent quantitative Alu PCR in fecal DNA as a non-invasive screening tool for colorectal cancer (CRC).

MATERIALS AND METHODS

Methylation-specific PCR (MSP) was performed to analyze TFPI2 gene promoter methylation status in a blinded fashion in stool samples taken from 30 endoscopically diagnosed healthy controls, 20 patients with adenomas, and 60 patients with colorectal cancer. Real-time Alu PCR was used to quantify human long DNA.

RESULTS

The specificity of fecal TFPI2 MSP assay and long DNA assay was 100% and 83.3%, respectively. The sensitivity of fecal TFPI2 MSP assay and long DNA assay was 68.3% and 53.3%, respectively. The sensitivity of fecal DNA assay (either marker being positive) was 86.7%, which was high for CRC.

CONCLUSIONS

Our results have demonstrated the feasibility of using TFPI2 methylation and quantify human long DNA with fluorescent quantitative Alu PCR in fecal samples as a new noninvasive test for CRC.

Fecal Tests: From Blood to Molecular Markers

Detection of molecular markers for colorectal neoplasia in feces has the potential to improve performance of simple noninvasive screening tests for colorectal cancer. Most research has explored the value of DNA-based, RNA-based, and protein-based markers. In all cases there has been a trend to move from a single marker to a panel of markers to improve sensitivity. Unfortunately, no type of molecular marker has proved specific for neoplasia. DNA tests have been improved by combining mutation detection with assessment of DNA integrity plus epigenetic markers of neoplasia. RNA-based approaches are just beginning to explore the full power of transcriptomics. So far, no protein-based fecal test has proved better than fecal immunochemical tests for hemoglobin. Finally, no marker or panel of markers has yet been developed to the point where it has been evaluated in large unbiased population studies to assess performance across all stages of neoplasia and in all practical environments.

FIT: a valuable but underutilized screening test for colorectal cancer-it's time for a change

Although fecal immunochemical tests (FITs) have been used for colorectal cancer (CRC) screening in several countries for years, this has not been the case in the United States. The reasons for this are multifactorial, but if the United States hopes to increase screening rates, the evidence is in regarding FIT's benefits and potential. A publication in this issue of the American Journal of Gastroenterology provides "gold standard" evidence of its superiority over the standard guaiac test and opens opportunities for investigators to discover the most effective uses of this test for population screening.

Mailed fecal-immunochemical test for colon cancer screening

Various interventions have been implemented to increase the rate of colon cancer screening. The purpose of this study was to determine if persons who are regular patients of a clinic, ages 50-64 years, and not up-to-date with colon cancer screening will complete the at-home fecal-immunochemical test (FIT) if it is mailed to them. This intervention was designed to have the subject avoid the signing of an informed consent and having to ask for the screening test; and, only one stool specimen was needed. Three hundred and fifty potential subjects were randomly selected from an electronic medical record database after meeting inclusion criteria. Eighty-seven fecal immunochemical tests were returned. Seven of the FIT kit results were positive for occult blood. Each respondent was sent a letter giving them their results. A minimal cue CRC screening intervention, a FIT kit sent in the mail without prerequisite of a signed informed consent, was offered to the study subjects. Twenty-six percent of the eligible persons were screened for colon cancer by this method. A mailed FIT kit or one handed to the patient at an office visit has minimal cost which can be recovered through insurance coverage. Commitment by health care providers is necessary for prevention. This method is one of several that could reach the hard to screen population.

Prediction of flare-ups of ulcerative colitis using quantitative immunochemical fecal occult blood test

AIM: To examine the feasibility of predicting the flare-up of ulcerative colitis (UC) before symptoms emerge using the immunochemical fecal occult blood test (I-FOBT).

METHODS: We prospectively measured fecal hemoglobin concentrations in 78 UC patients using the I-FOBT every 1 or 2 mo.

RESULTS: During a 20 mo-period, 823 fecal samples from 78 patients were submitted. The median concentration of fecal hemoglobin was 41 ng/mL (range: 0-392 500 ng/mL). There were three types of patients with regard to the correlation between I-FOBT and patient symptoms; the synchronous transition type with symptoms (44 patients), the unrelated type with symptoms (19 patients), and the flare-up predictive type (15 patients). In patients with the flare-up predictive type, the values of I-FOBT were generally low during the study period with stable symptoms. Two to four weeks before the flare-up of symptoms, the I-FOBT values were high. Thus, in these patients, I-FOBT could predict the flare-up before symptoms emerged.

CONCLUSION: Flare-up could be predicted by I-FOBT in approximately 20% of UC patients. These results warrant periodical I-FOBT in UC patients.

Combination of sigmoidoscopy and a fecal immunochemical test to detect proximal colon neoplasia

BACKGROUND & AIMS

The combination of sigmoidoscopy and a sensitive fecal occult blood test was recommended as one strategy for colorectal cancer screening by the US Preventive Services Task Force in 2008. However, there have been no studies to evaluate the sensitivity of a one-time screen that uses both flexible sigmoidoscopy and a fecal immunochemical test (FIT) to detect advanced colorectal neoplasia.

METHODS

We analyzed data from 21,794 asymptomatic persons who had undergone colonoscopy and a FIT. Analyses were performed with the following assumptions: colonoscopy would be performed for any positive FIT result; colonoscopy would be performed if the FIT result was negative and if advanced neoplasia was detected in the rectosigmoid (or plus descending) colon. The sensitivities and specificities of the combination of sigmoidoscopy and the FIT in detecting advanced neoplasia in the proximal colon were determined.

RESULTS

When colonoscopy was performed for a positive FIT result alone, for a positive sigmoidoscopy finding, and for a positive FIT result or sigmoidoscopy finding, the sensitivities in detection of advanced proximal neoplasia were 22.3%, 16.3%, and 31.7%, respectively. The sensitivities for detection of proximal invasive cancer were 58.3%, 8.3%, and 62.5%, respectively.

CONCLUSIONS

The combination of sigmoidoscopy and FIT can detect advanced proximal neoplasia better than either test alone. The incremental yield of advanced neoplasm detection by a screening program that uses both a FIT and sigmoidoscopy is approximately 10%. The FIT adds the most in terms of finding proximal cancers in a screening program that uses both tests. The combination of sigmoidoscopy and FIT is a viable and useful screening option.

Population-based screening for colorectal cancer: Australian research and implementation

Australia is one of the first countries in the world to implement an organized whole-of-population screening program for colorectal cancer (CRC). Australians have made broad contributions to CRC in general ranging from primary prevention through genetics, secondary prevention and treatment, to palliation. This overview focuses on some of the contributions of direct relevance to population-based screening, stretching from technology development to population-based controlled studies and health services research. In terms of simple screening tests in a two-step screening strategy, the evidence is overwhelming that fecal immunochemical tests for hemoglobin (FITs) improve detection and are more acceptable. FIT-based screening is clearly acceptable to Australians and it has been demonstrated that a national organized screening program is feasible. In terms of benefit for Australians, with full roll out and high uptake by the population we could see the number of cases dying from CRC halved by this strategy. To this will be added the extra-screening benefits of improved diagnosis, improved treatment and improved public awareness, all benefits of other screening programs. CRC screening has progressed from a matter of irrelevance and distaste, to commonwealth government policy in the context of an organized program for all Australians.

Fecal cyclooxygenase 2 plus matrix metalloproteinase 7 mRNA assays as a marker for colorectal cancer screening

We previously reported that fecal cyclooxygenase 2 (COX-2) mRNA assay, detecting COX-2 mRNA in feces, is useful for identifying subjects with colorectal cancer (CRC). To further improve the sensitivity, we evaluated the usefulness of the combination of COX-2 mRNA and matrix metalloproteinase 7 (MMP-7) mRNA assays as a marker of CRC. The study cohort included 62 patients with CRC and 29 control patients without colorectal neoplasia. RNA was isolated from routinely collected fecal samples. The expression levels of COX-2 and MMP-7 mRNAs were determined by nested reverse transcription-PCR. PCR conditions were optimized where the specificity of fecal COX-2 and MMP-7 mRNA assay result in 100%. The sensitivity of each fecal assay was 87% [95% confidence interval (95% CI), 76-94%] and 65% (95% CI, 51-76%) for CRC, respectively. The sensitivity of fecal RNA test (either marker being positive) was high for CRC (90%; 95% CI, 80-96%). The sensitivity of the fecal RNA test was also high (93%; 95% CI, 80-98%) in patients with stage I or II who are often cured by surgical resection. The fecal RNA test using COX-2 and MMP-7 mRNAs improved the sensitivity to detect CRC without decreasing the specificity. These results suggest that the fecal RNA test would be a promising approach for CRC screening, although larger clinical investigations are indicated.

Detection of colorectal cancer in symptomatic outpatients without visible rectal bleeding: Validity of the fecal occult blood test

Background:

In 2002, a new diagnostic strategy in symptomatic outpatients without known established colorectal cancer risk factors aged 40 years or older was implemented in Denmark. Fecal occult blood test (Hemoccult Sensa®) was a part of that strategy in patients without visible rectal bleeding.

Aims:

The aim was to assess the validity of the Hemoccult Sensa® test in detecting colorectal cancer in the above-mentioned outpatients.

Patients:

Symptomatic outpatients without known established colorectal cancer risk factors and without visible rectal bleeding.

Methods:

Hemoccult Sensa® was performed before endoscopic examination. Colorectal cancer was identified at histopathological examination. Patients completed a questionnaire about their symptoms before their first hospital appointment.

Results:

Eight of 256 patients were found to have colorectal cancer. Median patient age was 63 years. The positive predictive value, negative predictive value, sensitivity, and specificity of Hemoccult Sensa® for colorectal cancer were 10.5% (95% confidence interval [CI]: 6.8–14.3), 99.0% (95% CI: 97.8–100.0), 75.0% (95% CI: 69.7–80.3), and 79.4% (95% CI: 74.5–84.4).

Conclusions:

Hemoccult Sensa® as the initial examination in symptomatic outpatients without known established colorectal cancer risk factors presenting without rectal bleeding has to be used with caution. We did not find Hemoccult Sensa® test to be an acceptable alternative to flexible sigmoidoscopy.

[Chemical or immunological tests for the detection of fecal occult blood in colorectal cancer screening?]

Colorectal cancer (CRC) can be prevented by screening programs in the population at average risk (men and women aged between 50 and 74 years) and at high risk (first degree relatives, CRC hereditary syndromes and chronic inflammatory bowel disease). Early CRC (with submucosal invasion) and advanced adenomas (size > or =10mm, with severe dysplasia or >20% villous component) produce intermittent microscopic blood losses that can be detected through chemical and immunological testing for fecal occult blood (C-FOBT and I-FOBT). Among the screening strategies in the population at average risk, annual or biannual fecal occult blood testing is the most widely used due to its non-invasiveness and low cost. Four randomized clinical trials have shown that annual or biannual screening with guaiac-based tests (C-FOBT) reduces overall mortality due to CRC by 16% and CRC incidence by 20% and 17% respectively. However, these tests have major drawbacks, especially their low sensitivity in detecting early CRC and advanced adenoma, their lack of specificity in detecting human hemoglobin (Hb), and their high fecal Hb detection threshold (>300microgHb/gfeces). In the last few years, major developments have occurred in immunological tests (I-FOBT), based on an antigen-antibody reaction that specifically detects human Hb, and these tests are currently available as an alternative to C-FOBT. Their main advantages are as follows: firstly, I-FOBT specifically detect human Hb in stools and at much lower levels (40-300microgHb/gfeces) than C-FOBT; secondly, automated analysis avoids subjectivity in reading qualitative tests and allows large population groups to be studied in a short time, making I-FOBT ideal for population-based screening; thirdly, I-FOBT fairly accurately selects individuals for colonoscopy so that approximately half of patients with an I-FOBT test show clinically significant colorectal neoplasia (advanced adenoma or invasive CRC); fourthly, the cut-off point for fecal Hb detection can be modified, depending on the availability of endoscopic resources; fifthly, when cut-off points for fecal Hb of 50-150microgHb/gfeces are used, more than twice the number of CRC and advanced adenomas are detected than with C-FOBT, with a reasonable false-positive rate; and sixthly, I-FOBT are better accepted by the population due to their simplicity and ease of use, increasing participation in screening programs. For all these reasons, the current recommendation is that the new quantitative I-FOBT tests replace C-FOBT tests when the strategy of population-based screening through annual or biannual fecal occult blood testing is considered.

Screening for colorectal cancer

Although there are several methods available for colon cancer screening, none is optimal. This article reviews methods for screening, including fecal occult blood tests, flexible sigmoidoscopy, colonoscopy, CT colonography, capsule endoscopy, and double contrast barium enema. A simple, inexpensive, noninvasive, and relatively sensitive screening test is needed to identify people at risk for developing advanced adenomas or colorectal cancer who would benefit from colonoscopy. It is hoped that new markers will be identified that perform better. Until then we fortunately have a variety of screening strategies that do work.

Sensitivity of immunochemical fecal occult blood test to small colorectal adenomas

BACKGROUND

Although the immunochemical fecal occult blood test (FOBT) is reportedly more sensitive to large adenomas or colorectal cancer (CRC) than the guaiac-based FOBT, the sensitivity of the immunochemical FOBT to small adenomas has scarcely been reported. Previous reports have indicated that the guaiac-based FOBT can detect small adenomas only by serendipity.

OBJECTIVES

To investigate the sensitivity of immunochemical FOBT to small adenomas using a large-scale cohort.

METHODS

We analyzed 21,805 consecutively enrolled asymptomatic persons who underwent colonoscopy and immunochemical FOBT.

RESULTS

The sensitivity to adenomas </=9 mm was significantly higher than the false-positive rate as revealed by analysis of all eligible subjects (7.0%vs 4.5%, P < 0.001). In men, the sensitivity was superior to the false-positive rate and increased with age (<50 yr 6.1% and >60 yr 11.3%). On the other hand, the sensitivity in women was not significantly different from the false-positive rate in any generation (5.1%vs 4.7% for all eligible women, P= 0.72).

CONCLUSIONS

Immunochemical FOBT detected a small percentage of small adenomas in men at a rate that is significantly higher than the false-positive rate. Studies comparing the guaiac and immunochemical FOBTs using the end point of CRC-related death are expected.

Screening for Colorectal Neoplasms With New Fecal Occult Blood Tests: Update on Performance Characteristics

BACKGROUND

One type of fecal occult blood test (FOBT), the unrehydrated guaiac fecal occult blood test (GT), is recommended by the United States Preventive Services Task Force and the Institute of Medicine for use in screening programs, but it has relatively low sensitivity as a single test for detecting advanced colonic neoplasms (cancer and adenomatous polyps > or = 1 cm in diameter). Thus, improving the sensitivity of FOBT should make colon cancer screening programs that use these tests more effective.

METHODS

We assessed prospectively the performance characteristics of two newer FOBTs in 5841 subjects at average risk for colorectal cancer in a large group-model managed care organization. The tests evaluated included a sensitive GT, a fecal immunochemical test (FIT), and the combination of both tests. Patients with positive and negative test results were advised to have colonoscopy and sigmoidoscopy, respectively. Sensitivity and specificity for detecting advanced neoplasms in the left colon within 2 years after the FOBT screening were evaluated for the two tests administered separately and in combination.

RESULTS

A total of 139 patients were diagnosed with advanced colorectal neoplasms (n = 14 cancers, n = 128 adenomas) within the 2 years following their initial FOBT screening. Sensitivity for detecting cancer was 81.8% (95% confidence interval [CI] = 47.8% to 96.8%) for the FIT alone and 64.3% (95% CI = 35.6% to 86.0%) for the sensitive GT and the combination test. Sensitivity for detecting advanced colorectal adenomas was 41.3% (95% CI = 32.7% to 50.4%) for the sensitive GT, 29.5% (95% CI = 21.4% to 38.9%) for the FIT, and 22.8% (95% CI =16.1% to 31.3%) for the combination test. Specificity for detecting cancer and adenomas was 98.1% (95% CI = 97.7% to 98.4%) and 98.4% (95% CI = 98.0% to 98.7%), respectively, for the combination test; 96.9% (95% CI = 96.4% to 97.4%) and 97.3% (95% CI = 96.8% to 97.7%), respectively, for the FIT; and 90.1% (95% CI = 89.3% to 90.8%) and 90.6% (95% CI = 89.8% to 91.4%), respectively, for the sensitive GT.

CONCLUSIONS

The FIT has high sensitivity and specificity for detecting left-sided colorectal cancer, and it may be a useful replacement for the GT.

Performance characteristics and comparison of two fecal occult blood tests in patients undergoing colonoscopy

We investigated the use of a new type of FOBT (EZ-Detect) that uses the blood's pseudo-peroxidase activity as an enzymatic catalyst, in a one-step chromogen-substrate system performed by the patient. Asymptomatic patients >/=50 years old received three Hemoccult II (HO) cards and three EZ-Detect (EZ) packages to be used in three consecutive bowel movements. Sensitivity, specificity, positive predictive value, and negative predictive value for detection of colorectal neoplasia was calculated. The study included 207 patients, with a mean age of 58.9 years. Diagnostic accuracy for detection of adenomas was similar for the EZ and HO tests (66.7% vs. 71.0%; P=0.48), while for advanced adenomas diagnostic accuracy for the EZ and HO tests was 86.0% vs. 94.2% (P=0.01), respectively. Most patients preferred the EZ test (92% vs. 8%). We conclude that the EZ test has a diagnostic profile similar to that of the HO test for identification of adenomas; however, for advanced adenomas the diagnostic accuracy was slightly better for the HO. The EZ test was preferred by most patients, which may increase colorectal cancer screening compliance.

Comparison of a brush-sampling fecal immunochemical test for hemoglobin with a sensitive guaiac-based fecal occult blood test in detection of colorectal neoplasia

BACKGROUND

Fecal immunochemical tests (FIT) are an advanced fecal occult blood test (FOBT) technology that reduces barriers to population screening by simplifying the logistics of stool-sampling. The current study was conducted to undertake a paired comparison of a sensitive guaiac FOBT (GFOBT; Hemoccult II Sensa, Beckman Coulter, Fullerton, CA) with a brush-sampling FIT (InSure; Enterix, North Ryde, NSW, Australia), to determine whether this FIT improves detection of significant neoplasia.

METHODS

Individuals sampled consecutive stools, at home, with both FIT and GFOBT sampling devices while following dietary restrictions appropriate for GFOBT. Study populations included a screening cohort (n = 2351) and a symptomatic diagnostic group (n = 161). Paired comparison of positivity rates was undertaken in those found to have cancer and/or significant adenoma (high-grade dysplasia, villous change, > or =10 mm, serrated histology or > or =3 polyps), benign pathology, or no pathology.

RESULTS

Combined results for both cohorts showed that the FIT returned a true-positive result significantly more often in cancer (n = 24; 87.5% vs. 54.2%) and in significant adenomas (n = 61; 42.6% vs. 23.0%). Of all UICC Stage I cancers, the FIT was positive in 12 of 13 compared with 4 of 13 with the GFOBT (P = .002). In analyses of just the screening cohort, the FIT remained significantly better at detecting cancers and significant adenomas; the false-positive rate for any neoplasia was marginally higher with the FIT than the GFOBT (3.4% vs. 2.5%; 95% CI of difference, 0-1.8%), whereas positive predictive values were 41.9% and 40.4%, respectively.

CONCLUSIONS

This brush-sampling FIT is more sensitive for cancers and significant adenomas than a sensitive GFOBT. As such, it should deliver greater reductions in colorectal cancer mortality and incidence than the GFOBT.

Comparative evaluation of a new bedside faecal occult blood test in a prospective multicentre study

BACKGROUND

Faecal occult blood testing is an established method of colorectal neoplasia screening. Guaiac-based tests are limited by poor patient compliance, low sensitivity, specificity and positive predictive value. Newer immunochemical-based tests, accurate but tedious, require a well-established laboratory set up. There is need for simpler immunochemical tests that can be performed at the out-patient clinic.

AIM

To compare the performance characteristics of a new bedside immunological test strip device with a sensitive Guaiac-based and established immunochemical test for detection of faecal occult blood in patients undergoing colonoscopy.

METHODS

A total of 389 consecutive patients from four centres who were referred for colonoscopy also provided the stool samples for detection of occult blood without dietary restrictions. Stool tests performed were (i) Guaiac-based, (ii) immunochemical enzyme-linked immunosorbent assay and (iii) bedside immunochemical strip test.

RESULTS

At the optimal threshold level, the sensitivity and specificity of the beside immunochemical strip test for detection of significant colorectal neoplasia (adenomas >1.0 cm and carcinomas) were 60% and 95%, respectively.

CONCLUSIONS

This bedside immunochemical strip test proved to be a simple, convenient, non-cumbersome and accurate tool with similar performance characteristics for detection of any bleeding lesion including colorectal neoplasia when compared with an established immunochemical faecal occult blood test.

Prospective multicenter evaluation of fecal tumor pyruvate kinase type M2 (M2-PK) as a screening biomarker for colorectal neoplasia

Proliferating cells, particularly the tumor cells, express a dimeric isoenzyme of pyruvate kinase, termed M2-PK. It's a direct target of several oncoproteins; the determination of fecal tumor pyruvate kinase type M2 (M2-PK) might be another promising tool for colorectal cancer (CRC) screening. In this study, we have evaluated fecal M2-PK as a screening biomarker for colorectal neoplasia. It was compared against fecal occult blood (FOB) and colonoscopy. Three hundred and seventeen consecutive subjects from 4 different centers were included. Stool specimens were collected before purgation, processed appropriately and were tested for FOB and quantitatively analyzed for M2-PK. Colonoscopies were performed by experienced endoscopists who were unaware of fecal assay results. At cutoff value of 4 U/ml, fecal M2-PK assay had a sensitivity, specificity, PPV and NPV of 81.1, 86.7, 71.1 and 61.9% respectively for diagnosing CRC whereas FOBT showed a sensitivity of 36.5%, specificity of 92.2%, PPV of 72.9% and NPV of 71.5% for CRC. Such low specificity of fecal M2-PK will lead to unacceptably high number of false positives if it is used for mass CRC screening, leading to unindicated colonoscopies with its associated inconveniences, risks and costs. CRC screening test must have high specificity; a high sensitivity is not as vital. To conclude, M2-PK was found to be a poor screening biomarker for CR neoplasia in a subject population at above average risk based on its prospective comparison with colonoscopy. These marginal performance characteristics do not permit its use as a screening tool for CR neoplasia in present clinical settings.

Review article: Population screening for colorectal cancer

Colorectal cancer is a common cancer and common cause of death. The mortality rate from colorectal cancer can be reduced by identification and removal of cancer precursors, adenomas, or by detection of cancer at an earlier stage. Pilot screening programmes have demonstrated decreased colorectal cancer mortality; as a result many countries are developing colorectal cancer screening programmes. The most common modalities being evaluated are faecal occult blood testing, flexible sigmoidoscopy and colonoscopy. Implementation of screening tests has been hampered by cost, invasiveness, availability of resources and patient acceptance. New technologies such at computed tomographic colonography and stool screening for molecular markers of neoplasia are in development as potential minimally invasive tools. This review considers who should be screened, which test to use and how often to screen.

A comparison of the immunochemical fecal occult blood test and total colonoscopy in the asymptomatic population

BACKGROUND & AIMS

The fecal occult blood test (FOBT) is recommended as a screening test for colorectal cancer, but there are few reliable studies on the accuracy of immunochemical FOBT. The aim of this study was to analyze the sensitivity of immunochemical FOBT and to compare the results with the findings from complete colonoscopy.

METHODS

Asymptomatic adults underwent 1-time immunochemical FOBT and total colonoscopy simultaneously. The prevalence and location of colorectal neoplasia were determined by colonoscopy. The results of immunochemical FOBT and the colonoscopic findings were compared.

RESULTS

Of 21,805 patients, immunochemical FOBT was positive in 1231 cases (5.6%). The sensitivity of 1-time immunochemical FOBT for detecting advanced neoplasia and invasive cancer was 27.1% and 65.8%, respectively. In addition, the sensitivity for invasive cancer according to Dukes' stage showed 50.0% for Dukes' stage A, 70.0% for Dukes' stage B, and 78.3% for Dukes' stages C or D. The sensitivity for detecting advanced neoplasia at the proximal colon was significantly lower than that detected in the distal colon (16.3% vs 30.7%, P = .00007).

CONCLUSIONS

Although the screening of asymptomatic patients with immunochemical FOBT can identify patients with colorectal neoplasia to a certain extent, the sensitivity is relatively low and different according to the tumor location. Therefore, programmatic and repeated screening by immunochemical FOBT may be necessary to increase sensitivity for colorectal cancer detection.

Screening of patients at average risk for colon cancer

Both the incidence and the mortality from colorectal cancer can be substantially reduced by primary and secondary prevention. There are many screening tests for colorectal cancer, and any test should result in a reduction in colorectal cancer incidence and mortality. If the age-eligible population undergoes these screening tests, the burden of colorectal cancer should be substantially reduced. The scientific evidence related to secondary prevention, specifically screening of individuals at average risk for colorectal cancer, is presently reviewed.

Fecal occult blood screening--trial evidence, practice and beyond

Colorectal cancer is a leading cause of morbidity and mortality in Western countries. Primary prevention and early detection of this malignancy has been shown in multiple research set-ups, and using different modalities, to be effective in reducing the incidence and mortality rates of this disease. Three randomized controlled trials have been conducted over the last 30 years to evaluate the efficacy of periodic screening with fecal occult blood tests (FOBT). These studies have consistently demonstrated mortality reduction with biennial as well as annual testing after 8-18 years of follow-up. A significant primary prevention effect through reduction of colorectal cancer incidence was also reported. The results of the Israeli population-based screening program using Hemoccult Sensa show that it is possible to achieve a high detection rate in a well-organized community set-up and, in addition, also a shift in tumor stage towards smaller tumors, a low positivity rate, and an acceptable false positivity rate. FOBT is cheap and performs very well in cost effectiveness analyses evaluating the cost of detecting one cancer. This is quite a rare situation where mortality reduction can be achieved with a simple rather than a sophisticated technology. Research to further enhance the cancer detection capabilities of FOBT through the incorporation of molecular testing of the stool for tumor genes is underway. Multiple policymakers are already recommending this procedure for routine screening of average risk population. Taking their recommendations into action is of major importance.

Prevention of advanced colorectal cancer by screening using the immunochemical faecal occult blood test: a case-control study

To evaluate colorectal cancer screening with faecal occult blood testing (FOBT) in terms of prevention of advanced cancers, we conducted a case-control study in the areas where an annual screening programme with immunochemical FOBT has been offered to all inhabitants aged 40 years or over. Cases were 357 consecutive patients in the study areas clinically diagnosed as having advanced colorectal cancer or a tumour invading the muscularis propriae or deeper, that is, T(2)-T(4) in TNM classification. Three controls were selected for each case matched by gender, age, residential area and exposure status to screening within 1 year before case diagnosis. The odds ratios (ORs) of developing advanced cancer were calculated using conditional logistic regression analyses. The OR for those screened within 3 years before the diagnosis vs those not screened was 0.54 (95% confidence interval (CI) 0.29-0.99). The ORs were lower for rectum than for colon (0.32-0.73 and 0.84-1.18 for rectum and colon, respectively). For those screened within the past 3 years, OR of developing advanced cancer in the rectum was 0.32 ( 95%CI: 0.12-0.84). A screening programme with immunochemical FOBT can be effective for prevention of advanced colorectal cancer. Risk reduction appears to be larger for rectal than for colon cancer. British Journal of Cancer (2003) 89, 23-28. doi:10.1038/sj.bjc.6601002 www.bjcancer.com

Emerging role of calprotectin in gastroenterology

Calprotectin is a calcium and zinc binding protein of the S100 family derived predominantly from neutrophils and monocytes. It is detectable in body fluids and tissue samples and is emerging as a valuable marker in the diagnosis, and the monitoring and determining of the prognosis of commonly encountered gastroenterological conditions. Fecal calprotectin, in particular, has for a long time been regarded as a promising marker of gastrointestinal pathology and has now been established as a routine test in Norway and at several centers in the UK.

Evaluation of an automated immunochemical fecal occult blood test for colorectal neoplasia detection in a Chinese population

BACKGROUND

Most commercial fecal occult blood tests (FOBT) used for colorectal carcinoma screening of Western populations are guaiac-based, manually developed, subjective, and sensitive to dietary components. Preliminary studies demonstrated the unsuitability of these tests for screening a Chinese population. The goal of the current study was to evaluate the performance characteristics of a human hemoglobin-specific automated immunochemical FOBT, the Magstream 1000/Hem SP (Fujirebio, Inc., Tokyo, Japan), in a Chinese population referred for colonoscopy.

METHODS

Two hundred fifty consecutive patients who were referred for colonoscopy and met the study inclusion criteria provided samples for the immunochemical FOBT (without dietary restrictions) from two successive stool specimens. Tests were developed with an automated instrument that had an adjustable sensitivity threshold. The sensitivity, specificity, and positive predictive value for detecting colorectal adenomas and carcinomas were calculated according to the manufacturer's instructions over a range of sensitivity levels.

RESULTS

At the optimal threshold level, the sensitivity, specificity, and positive predictive value for detection of significant colorectal neoplasia (adenomas >or= 1.0 cm and carcinomas) were 62%, 93%, and 44%, respectively. The test was easy to use, and results did not depend on operator experience.

CONCLUSIONS

The automated immunochemical FOBT used in the current study was a robust, convenient, and useful tool for colorectal carcinoma screening in the study population.

Development of a fecal occult blood test using a monoclonal antibody to haptoglobin

Monoclonal antibodies (mAbs) were produced to human haptoglobin by immunising with fecal extracts from patients with colon cancer. An enzyme-linked immunosorbent assay was developed with one of the mAbs (FE14.1), and its ability to diagnose colorectal carcinoma evaluated. Patients with colorectal cancer were positive (43/46 = 93.5%) compared to normal individuals (4/211 = 1.9%). The assay has a specificity 93.5% and sensitivity 98.1% and has several advantages over current fecal occult blood tests. The test is potentially useful for bowel cancer diagnosis and to quantitate the level of haptoglobin in other body fluids such as urine and in effusions.

Applying evidence-based guidelines improves use of colonoscopy resources in patients with a moderate risk of colorectal neoplasia

OBJECTIVES

To determine whether applying National Health and Medical Research Council (NHMRC) guidelines for colorectal cancer prevention would reduce the number of follow-up colonoscopies.

DESIGN

A prospective audit of colonoscopic surveillance decisions before and after the intervention.

SETTING

The endoscopy suite at a metropolitan tertiary hospital three months before and after January 2000.

INTERVENTION

Dissemination of NHMRC guidelines, and supervision of application of the guidelines by a nurse coordinator.

SUBJECTS

We compared colonoscopic surveillance decisions before and after the intervention in two groups of 100 consecutive patients after polypectomy and in two groups of 50 consecutive patients with a family history of colorectal cancer after a normal colonoscopy.

MAIN OUTCOME MEASURES

Change in concordance of decisions with NHMRC guidelines; and effect on number of follow-up colonoscopies.

RESULTS

After the intervention, the proportion of postpolypectomy surveillance decisions matching the guidelines increased from 37% to 96% (P < 0.05). The mean time to repeat colonoscopy after polypectomy increased from 2.7 to 3.5 years (P < 0.005) (ie, a 23% reduction in the number of postpolypectomy surveillance colonoscopies performed per year). Likewise, the proportion of family-history surveillance decisions matching the guidelines increased from 63% to 96%. Adhering to the guidelines resulted in a 17% reduction in colonoscopies performed on the basis of a family history of colorectal cancer.

CONCLUSIONS

Supervised application of evidence-based guidelines to a colorectal cancer surveillance program significantly reduces the number of surveillance colonoscopies performed.

The advanced adenoma as the primary target of screening

The advanced adenoma bridges benign and malignant states and may be the most valid neoplastic surrogate marker for present and future colorectal cancer risk. We define the advanced adenoma as an adenoma with significant villous features (>25%), size of 1.0 cm or more, high-grade dysplasia, or early invasive cancer. Prevention studies should demonstrate a high efficacy in reducing the number of advanced adenomas. We should use the advanced adenoma in the evaluation of new screening technology, nutritional interventions, and chemoprevention agents because the advanced adenoma is a more desirable target for screening efficacy than is the more uncommon but life-threatening cancer stage or the more common but early, less significant small adenoma stage.

Effect of dietary restriction on participation in faecal occult blood test screening for colorectal cancer

OBJECTIVES

To determine if participation in colorectal cancer screening using faecal occult blood testing (FOBT) is affected by a restrictive diet and if it is associated with certain demographic variables.

PARTICIPANTS AND SETTING

1,203 residents of South Australia aged 50-69 years, with no "currently active bowel disease", randomly selected from a database of people willing to be contacted about unspecified health issues.

DESIGN

Randomised controlled trial: participants were offered screening by immunochemical FOBT by mail in 1998. Half were randomly allocated to a group instructed to follow a low-peroxidase diet, as required for guaiac FOBT, while the other group was not so restricted.

MAIN OUTCOME MEASURES

Effect of diet restriction on participation (return of correctly completed FOBT sample cards within 15 weeks); time taken to return cards; relationships between participation and demographic variables.

RESULTS

Participation rates were 65.9% (no-diet group) and 53.3% (diet group) (difference, 12.6%; 95% CI, 7.1%-18.1%). In the first week, rates of return as a proportion of all tests returned were 13.1% (no-diet) and 1.6% (diet) (difference, 11.5%; 95% CI, 8.6%-14.4%), increasing to 54.3% and 44.5%, respectively, after five weeks (difference, 9.8%; 95% CI, 4.2%-15.4%). Participation was significantly associated with older age (odds ratio, 1.40; 95% CI, 1.10-1.78), but not sex, Index of Social Disadvantage or rural versus urban address.

CONCLUSIONS

Dietary restrictions create a barrier to FOBT-based screening for colorectal cancer. The use of immunochemical rather than guaiac FOBT removes this barrier.