Screening for colorectal carcinoma: an analysis of the sensitivity of haemoccult

Use and abuse of fecal occult blood tests: a community hospital experience

Background

The Fecal Occult Blood Test (FOBT) is one of the diagnostic modalities indicated for screening patients for Colorectal Cancer (CRC). Despite being approved only for screening for CRC, numerous studies in the past have illustrated misuse of the FOBT. We examined utilization of the FOBT for patients admitted to a community teaching hospital.

Methods

The study was conducted at Saint Joseph Hospital, Chicago USA. A retrospective review of Electronic Medical Records (EMRs) of patients admitted from January 2016 to December 2017 was performed.

Results

We reviewed the EMRs of 729 patients who received the stool testing for occult blood (FOBT). All tests (100%) were carried out for purposes other than CRC screening. Anemia (38%) was the most common reason documented for carrying out the FOBT. Further, 88% of the tests were ordered on patients who either did not fulfill CRC screening criteria or had other contraindications for testing. Usage of contraindicated medication was the most important factor (58% of patients) that made the candidates ineligible for testing. A total 73 Colonoscopies were ordered for patients who received the test inappropriately with a resulting low yield (0.47%) of CRC diagnosis.

Conclusion

The stool occult blood test continues to be utilized for reasons other than CRC screening. Majority of patients who underwent the test were not suitable candidates due to the presence of contraindications for testing. Unsuitable FOBT testing led to further unnecessary investigations.

Impact of bowel cancer screening on the management of colorectal cancer

AIM

The National Bowel Cancer Screening Programme (NBCSP) was introduced in the West Midlands in 2006. Studies, including the UK Bowel Cancer Screening Pilot, have reported an 18% reduction in mortality. This regional study assesses the impact of screening on elective and emergency colorectal cancer (CRC) surgery.

METHOD

Data were extracted from the West Midlands cancer registration database for CRC diagnosed in residents of the West Midlands between 1998 and 2010. Screen-detected cancers were identified by matching to the NBCSP database. Mode of admission and intervention was obtained by matching to Hospital Episode Statistics and the classification of Interventions and Procedures code.

RESULTS

Of 42,082 patients diagnosed with CRC, 30,309 received surgical treatment. From 1998 to 2005, the number of patients who underwent emergency surgery increased from 4362 to 18,357, with the proportion each year remaining constant (23.85 ± 0.95% each year). In the screening age group (60-69 years) over the same period, emergency surgery was performed in 918 of 4831 patients (19.15 ± 1.65% each year). Following the introduction of screening, the emergency surgery rate decreased each year, reaching 16% (406/2520) in all patients and 12% (101/829) in the screening age group in 2010 (P < 0.001). These changes in emergency surgery were mirrored by increases in elective surgery.

CONCLUSION

The NBCSP has had a positive impact on elective and emergency surgery for CRC in the West Midlands.

Does the location of colorectal carcinoma differ between screened and unscreened populations?

AIM

Screening for colorectal malignancy using faecal occult blood testing is established across the UK. In NHS Grampian the programme was introduced in 2007. Previous studies have reported no difference in anatomical locations of cancers detected by screening programmes compared with those in unscreened populations. This study aims to review the location of tumours detected in an established screening programme compared with those diagnosed through symptomatic presentation within the same population.

METHOD

All patients discussed at the regional multidisciplinary meeting between June 2007 and August 2011 were included. Data were collated prospectively from multidisciplinary team records while site of tumour was documented from radiology, endoscopy, operative and pathology reports. Comparative statistics (χ(2) ) were performed using spss 19.

RESULTS

Of 1487 patients included 255 were detected via the screening programme and 1232 from symptomatic presentation. More left sided tumours (splenic flexure to rectosigmoid) were detected via screening (P=0.005). Of non-screened patients (n=1232), 456 (37%) tumours were right sided (caecum to distal transverse colon), 419 (34%) were left sided and 357 (29%) were in the rectum. This compares with the screened group (n=255): right sided 74 (29%), left sided 113 (44%) and rectal 68 (27%).

CONCLUSION

More left sided tumours appear to be detected in screened patients compared with symptomatic presentation, contrary to previously published work. These results may be worthy of further consideration given the ongoing debate on the optimal means of screening.

Does the location of screen-detected cancers differ from that seen in the unscreened population?

OBJECTIVE

It is important that screening detects cancers regardless of their location within the colon. The aim of this study was to see if the location of cancers detected by the pilot screening programme differs from that of unscreened cancers.

METHOD

The colorectal cancer dataset of University Hospital Coventry was analysed retrospectively. A 7-year period was used to include all three rounds of the pilot screening. Two groups of patients were selected, those with colorectal cancers detected by the screening programme and those detected outside of screening. The tumour location was compared in the two groups statistically (chi-squared test).

RESULTS

One thousand four hundred-ninety patients were included, 100 of whom were in the screened population and 1390 were in the unscreened population. There was no significant difference in tumour location between the two groups (P = 0.49).

CONCLUSION

This study showed that screen-detected cancers do not differ in their location from unscreened cancers and suggests that faecal occult blood testscreening detects cancer irrespective of location within the colon.

Time trends in colon cancer incidence and distribution and lower gastrointestinal endoscopy utilization in Manitoba

OBJECTIVES

There are limited data on recent trends in subsite-specific colon cancer incidence and utilization of lower gastrointestinal endoscopy from Canada. The aim of our study was to determine the concomitant trends in right-sided colon cancer incidence and utilization of colonoscopy and flexible sigmoidoscopy (FS) in Manitoba.

METHODS

Cases of colon cancer diagnosed from 1964 to 2004 were identified from the Manitoba Cancer Registry. Lower gastrointestinal endoscopies performed between 1984 and 2003 were identified from Manitoba Health's Physician Claims database. Trends of age-standardized incidence rates were determined using Joinpoint analyses.

RESULTS

Rates of right-sided colon cancer showed a monotonic increase in both sexes (annual percent change [APC] in both sexes 1.04%, P < 0.001). The most rapid increase (200%) occurred in individuals of 70 yr of age and older. While rates of colonoscopies without polypectomies quadrupled between 1985 (257 per 100,000) and 2003 (1,083 per 100,000, APC 8.89%, P < 0.001), rates of colonoscopies with polypectomies quadrupled from 35 per 100,000 in 1985 to 140 per 100,000 in 2000, and then increased more rapidly in the subsequent 4 yr (233 per 100,000 in 2003, APC 20%, P < 0.001). Rates of FS declined between 1999 (342 per 100,000) and 2003 (257 per 100,000, APC -6.68%, P= 0.01).

CONCLUSIONS

The rates of right-sided colon cancer are continuing to increase in Manitoba, with the most rapid increase occurring in older individuals. Reasons for the increasing incidence of right-sided colon cancer despite increasing rates of colonoscopy need to be further explored, and may reflect increased detection of asymptomatic cancers or a real increase in right-sided colon cancer incidence.

Screening for colorectal cancer

Screening for a disease is an important concept in modern day preventive medicine. The aim is early disease detection and treatment of both asymptomatic individuals and those at risk of the disease, with the goal of better survival. The WHO published a set of essential criteria for screening in 1968 and colorectal cancer has been identified as a candidate disease. Three methods of screening are evaluated here: fecal occult blood test, flexible sigmoidoscopy and colonoscopy. Newer techniques are still being studied and preliminary results are encouraging. The incidence of colorectal cancer in Asia has been increasing in association with changes in lifestyle and therefore, designing efficient, acceptable screening programs for these populations is an important issue in the prevention of this common malignant disease.

Colorectal cancer screening

Colorectal cancer causes significant morbidity and mortality in the United States. The incidence of colorectal cancer increases at age 50, approximately. Risk factors that have been identified include a personal history of colorectal cancer or adenomas, a family history of colon cancer or adenomas, inherited colorectal cancer syndromes, and long standing inflammatory bowel disease. Several screening tests have been developed for colorectal cancer prevention. Surveillance strategy is based on an individual's colorectal cancer risk. This article reviews fecal occult blood testing, flexible sigmoidoscopy, colonoscopy, barium enema, and genetic testing.

Colorectal cancer screening

Colorectal cancer is an important problem in the United States, with over 130,000 new cases and 55,000 deaths each year. There is now strong evidence that screening for colorectal cancer with fecal occult blood testing can decrease mortality, and additional evidence that removing benign adenomas can decrease cancer incidence. Evidence-based screening guidelines depend on colorectal cancer risk. Individuals at higher risk because of a personal or family history deserve more intensive screening than asymptomatic individuals over age 50.

Faecal occult blood screening and reduction of colorectal cancer mortality: a case-control study

To estimate the efficacy of screening on colorectal cancer mortality, a population-based case-control study was conducted in well-defined areas of Burgundy (France). Screening by faecal occult blood test prior to diagnosis in cases born between 1914 and 1943 and who died of colorectal cancer diagnosed in 1988-94 was compared with screening in controls matched with the case for age, sex and place of residence. Cases were less likely to have been screened than controls, with an odds ratio (OR) of 0.67 [95% confidence interval (CI) 0.48-0.94]. The negative overall association did not differ by gender or by anatomical location. The odds ratio of death from colorectal cancer was 0.64 (95% CI 0.46-0.91) for those screened within 3 years of case diagnosis compared with those not screened. It was 1.14 (95% CI 0.50-2.63) for those screened more than 3 years before case diagnosis. There was a negative association between the risk of death from colorectal cancer and the number of participations in the screening campaigns. The inverse association between screening for faecal occult blood and fatal colorectal cancer suggests that screening can reduce colorectal cancer mortality. This report further supports recommendations for population-based mass screening with faecal occult blood test.

Community screening for colorectal cancer in north-eastern New South Wales, 1987-1996

OBJECTIVE

To analyse results of Bowelscan, a community-based colorectal cancer screening program using Hemoccult II, and targeting people aged 40 years and over.

DESIGN

Survey of data from medical practitioners on follow-up of positive tests.

SETTING

North-eastern New South Wales (Rotary District 9650), 1987-1996.

SUBJECTS

3845 people with positive results for faecal occult blood.

OUTCOME MEASURES

Investigations performed; final diagnoses; number, site and Dukes' stage of colorectal carcinomas; number and histological diagnosis of colorectal polyps.

RESULTS

239,500 Hemoccult II kits were distributed between 1987 and 1996, with an estimated return rate of 80%-85%. Positive results for faecal occult blood were reported for 3845 tests (1.6% of those distributed), with 78% of these investigated by colonoscopy and/or barium enema. Investigation resulted in diagnosis of 260 colorectal carcinomas in 252 people (6.7%); 74 of these (29%) were in the caecum or ascending or transverse colon. Dukes' tumour stages were: A, 107 (41%); B, 86 (33%); C, 49 (19%); D, 16 (6%); and unknown, 2 (0.8%). (Corresponding figures from the NSW Central Cancer Registry were: A and B, 48%; C, 26%; D, 14% and unknown 12%) [corrected]. Colorectal polyps were found in a further 819 people (21.3%), and were adenomatous in 577 (79% of the 733 in whom histological diagnosis was available). Other gastrointestinal conditions were found in 1343 people (34.9%), while no cause was found for the positive result, despite adequate investigation, in 873 (22.7%).

CONCLUSION

Community-based screening with faecal occult blood testing detected colorectal carcinomas at earlier histological stages than colorectal carcinomas reported to the Cancer Registry and should reduce mortality from this disease. Treatment and follow-up of adenomatous polyps detected by such a program might minimise the incidence of colorectal carcinoma in this group.

Colorectal cancer mass-screening: estimation of faecal occult blood test sensitivity, taking into account cancer mean sojourn time

Mass screening using the faecal occult blood test (FOBT) can reduce mortality from colorectal cancer. Reliable estimation of FOBT sensitivity is crucial in assessing the potential effectiveness of a mass-screening procedure. Available estimates could be inaccurate because they neglect the temporal aspect of screening. The aim of our study was to estimate the sensitivity of the FOBT in mass screening for colorectal cancer, taking into account the duration of the pre-clinical phase of the disease assessed by the mean sojourn time (MST), and to assess whether MST and FOBT sensitivity differ according to cancer subsite. We analysed data taken from the first round of the mass-screening programme of the department of Calvados (France), involving 164,364 subjects of whom 43.4% participated in FOB screening. MST and sensitivity were estimated using a simple empirical approach, a traditional maximum likelihood method and log-linear modelling using the Bayesian technique of Gibbs sampling. MST was estimated as between 4.5 and 5 years for all subsites combined. According to the Gibbs sampling method, MSTs were 3.5, 6.4 and 2.6 years for proximal colon, distal colon and rectal cancer, respectively. Our estimation methods give a low sensitivity for the FOBT (50%), results for different subsites being closer to each other, slightly higher for proximal cancer. Our results strongly suggest that tumour growth rates are very different according to subsite, slowest for distal cancer and speediest for rectal cancer. Consideration of FOBT sensitivity without MST appears unreliable. Our results by subsite suggest that combining FOBT and sigmoidoscopy could be a good strategy for colorectal cancer screening.

Fecal occult blood screening in the Minnesota study: sensitivity of the screening test

BACKGROUND

In the Minnesota Colon Cancer Control Study, which used guaiac slides to annually screen stool samples for blood, mortality from colorectal cancer was reduced by 33.4%. The reported sensitivity of this test for colorectal cancer was about 90%. However, results from another study estimated the sensitivity to be 25%-33%; other investigators have reported intermediate values. Given these contradictions, we examined screening sensitivity for colorectal cancer in the Minnesota study by several direct and indirect methods.

METHODS

In this reanalysis of data from the Minnesota study, we distinguished between sensitivity for colorectal cancer of the screening test (composed of six slides) and of the screening program (a series of such tests). We estimated screen sensitivity by adjusting the crude estimate from the final tests in each screening phase for colorectal cancer incidence in 5 years of follow-up, by modeling guaiac slide results at each screen as a function of the presence of occult blood, and by incorporating sensitive detection into a modification of a mathematical model developed by Lang and Ransohoff. Program sensitivity was estimated from the fraction of screen-detected cancers among all cancers diagnosed in screened individuals.

RESULTS

The crude estimate of program sensitivity was 89.4%, whereas the modified Lang-Ransohoff model estimates screen sensitivities at 94.1%-96.2%, consistent with the estimates from the other methods. Indirect measures, such as the association between the number of positive slides among the six slides in each set and the positive predictivity for colorectal cancer, are consistent with these estimates.

CONCLUSIONS

The Minnesota study reduced mortality from colorectal cancer through use of a screening test with average screen and program sensitivities of about 90%.

Screening for colorectal cancer by immunochemical fecal occult blood testing

Screening for colorectal cancer using the conventional Hemoccult test has been shown to reduce mortality associated with cancer by 33% through a randomized controlled trial. However, the magnitude of effectiveness is small in terms of cost-effectiveness. The recently developed immunochemical fecal occult blood test (IFOBT) provides a potential replacement for the Hemoccult test as a screening test, due to its superior performance characteristics such as higher sensitivity shown in preliminary studies and the fact that it does not require any dietary restriction. The IFOBT method is reviewed, especially in relation to its specificity. In known colorectal cancer subjects, IFOBTs have shown both higher sensitivity and specificity than the Hemoccult test. Similarly, IFOBT has demonstrated a higher sensitivity than Hemoccult for colorectal cancer in an asymptomatic population. A nationwide screening program in Japan has demonstrated the feasibility of this approach for large population screening. However, the positivity rate varied according to the conditions at each screening facility. Therefore, technical factors that influence the positivity rate of IFOBTs in the screening program are discussed. Case-control studies have strongly suggested that screening using IFOBT would reduce mortality from colorectal cancer by 60% or more. Several observational studies have provided support for this estimate. The feasibility and effectiveness of population-based screening by IFOBT are discussed.

A case-control study to evaluate efficacy of screening for faecal occult blood

OBJECTIVES

Faecal occult blood testing is routinely used for early detection of colorectal cancer, but evidence of its efficacy in preventing death from colorectal cancer is limited. A case-control study was carried out to evaluate whether screening for faecal occult blood is associated with a reduced risk of fatal colorectal cancer.

SETTING

A health maintenance organisation in western Washington State, which has offered its members faecal occult blood testing every two years since 1983.

METHODS

Cases (n = 248) were members of the health maintenance organisation who died from colorectal cancer between 1986 and 1991. For each case, two control subjects, who did not die from colorectal cancer and who were similar to each case in age, gender, and year of enrollment at the health maintenance organisation, were randomly selected from the membership list of the year in which the case was diagnosed (n = 496). Information about episodes of faecal occult blood testing (including the location and reason for the test, and the evaluation of positive tests) and potential confounders was obtained from medical records.

RESULTS

Cases were less likely than controls to have ever been screened (odds ratio (OR) = 0.7, 95% confidence interval (CI) 0.5 to 1.0), consistent with a beneficial impact of screening. There was little difference, however, for screening that had taken place within a three year period before diagnosis (OR = 0.9, 95% CI 0.6 to 1.2), the maximum interval during which most tumours ought to have been detectable by faecal occult blood testing. A reduction in risk was seen for home testing but not for office testing, and in individuals aged less than 75 but not in those aged 75 or older. Although most of the 21 controls with a positive faecal occult blood test underwent some additional testing, only five (24%) were evaluated with colonoscopy or air contrast barium enema.

CONCLUSIONS

While there can be uncertainty as to whether specific faecal occult blood tests were performed as screening or diagnostic tests, those performed at home and in younger persons may be relatively less likely to be diagnostic tests that were misclassified as screening. Thus the modest reduced risk associated with faecal occult blood testing in these settings/persons may reflect genuine benefit. However, the presence of a reduced risk associated with a screening faecal occult blood test received in the past, well before a tumour or polyp might bleed enough to allow detection, is compatible with uncontrolled confounding. Interpretation is further complicated by the fact that a number of individuals in the study group who had positive test results underwent limited or no diagnostic testing. Thus our results should be interpreted with considerable caution.

Screening for colorectal cancer using an immunochemical test for faecal occult blood: results of the first 2 years of a South Australian programme

This paper reports an evaluation of the first 2 years of a South Australian screening programme for colorectal cancer which was established in 1988 by the Institute of Medical and Veterinary Science. The programme uses an immunochemical test for faecal occult blood. Based on 1 year of follow-up, over the period of this analysis there were 24 cancers and 99 adenomas detected in 6208 participants, and the estimated sensitivity and specificity of the test (for colorectal cancer) were 82.8 and 95.9%, respectively. In many cases the test was used to detect recurrence of disease in individuals with a previous diagnosis of colorectal cancer. The estimated predictive value of a positive test for colorectal cancer in this population was 7.5%. Results suggest that participants belonged to higher-than-average socio-economic groups and were more likely than the general population to have a family history of colorectal cancer. Almost one-third had suffered from bowel symptoms in the 6 months before taking the test. These unique characteristics of participants, which limit the generalizability of results to the wider population, may result from the programme's reliance on self-recruitment methods. Consistent evidence for improvements in mortality in populations screened for colorectal cancer is still required before a recommendation for widespread screening in Australia can be made.

Population screening for colorectal cancer: comparison between guaiac and immunological faecal occult blood tests

There is concern about the low sensitivity of the guaiac-based Haemoccult test in mass population faecal occult blood (FOB) screening for the early detection of colorectal carcinoma. Hemeselect, an immunological FOB test, has been shown to be more sensitive for symptomatic colorectal cancer and may prove to be a more reliable screening method. In Brighton and Guildford, 4018 asymptomatic subjects aged 50-75 years were offered screening with Haemoccult and Hemeselect. A total of 1489 (37.7 per cent) completed both tests, of which 17 (1.1 per cent) were positive for Haemoccult and 145 (9.7 per cent) positive for Hemeselect (a total of 148 subjects had positive tests). Seven subjects (4.7 per cent) refused to be investigated. Colonic investigation in the remainder revealed nine cancers and 49 patients with 67 adenomas (32 tumours 1 cm or more in size). All cancers (Dukes A, six; B, one; C, two) were detected by Hemeselect (positive predictive value 6.2 per cent) but only one patient was Haemoccult positive (positive predictive value 5.9 per cent). Hemeselect detected 65 adenomas (31 of 1 cm or more) in 48 patients (positive predictive value 33.1 per cent) compared with 11 adenomas (seven of 1 cm or more) in eight patients who were positive for Haemoccult (positive predictive value 47.1 per cent). The test specificity for neoplasia was respectively 94.9 and 99.6 per cent. The Hemeselect positive rate is high but its substantial positive predictive value for cancer warrants continuing evaluation.