Evaluation of an immunochemical test for faecal occult blood in screening for colorectal neoplasia in a high risk group

A group of 1615 asymptomatic individuals presumed to be at increased risk of colorectal neoplasia were selected as the study group. All were tested by an immunochemical test for faecal occult blood. In the second half of the study, individuals who were occult blood negative were offered colonoscopy. Ninety-nine individuals (6.1%) returned stools which were occult blood positive. Investigation by full colonoscopy was possible in 90 cases, revealing nine patients (10%) with invasive cancers, four patients (4.4%) with carcinomata in situ, and 36 patients (40%) with adenomata. Non-neoplastic pathology capable of producing occult blood positive stools was found in 31 individuals (34.4%). No pathology was found in 10 instances (11.1%). Of the 53 occult blood negative subjects who underwent colonoscopy, eight were found to have adenomata. Only one of these was larger than 5 mm in diameter (18 mm). No carcinomata were found. The site within the large bowel of the tumour did not appear to significantly affect the occult blood status of the faeces but the size of the tumours detected suggests that the presence of blood within the stool is more likely to be associated with larger lesions. The frequency of detection of both carcinomata and adenomata was greatest in individuals who had a past history of colorectal neoplasia. The individual cost of this immunochemical test is nominal. The high diagnostic yield and low false positive and negative rates suggest that case follow-up, surveillance, or screening utilizing this test is justified.     

Lower gastrointestinal symptoms are not predictive of colorectal neoplasia in a faecal occult blood screen-positive population

BACKGROUND: The aim of this study was to evaluate the incidence of lower gastrointestinal symptoms in faecal occult blood (FOB) test-positive participants in a colorectal screening programme, and to compare the colonoscopic findings in symptomatic and asymptomatic individuals. METHODS: Five hundred and sixty-three consecutive individuals with a positive FOB test in the Scottish arm of the national colorectal cancer screening pilot were studied. All were aged between 50 and 69 years and underwent colonoscopy. Before the procedure the participants were given a standard questionnaire to elicit gastrointestinal symptoms; these were correlated with the colonoscopic findings. RESULTS: Of the 563 participants, 439 (78.0 per cent) had one or more lower gastrointestinal symptoms and 124 (22.0 per cent) were symptom free. Taking adenoma and carcinoma together, 322 (57.2 per cent) of the subjects were found to have colorectal neoplasia, and 128 (22.7 per cent) had a completely normal colon. Rectal bleeding was the most common symptom, followed by change in bowel habit, abdominal pain, tenesmus, unexplained weight loss, rectal pain and unexplained anaemia. No significant associations were found between any of these symptoms and the findings at colonoscopy. CONCLUSION: In a FOB test-positive screened population, lower gastrointestinal symptoms are common, but are not predictive of colorectal neoplasia.     

Faecal occult blood screening for colorectal neoplasia: a randomized trial of three days or six days of tests

Haemoccult, a guaiac test for faecal occult blood, detects 56-78 per cent of asymptomatic carcinomas when performed over 3 days. In patients with known colorectal cancer the sensitivity of the test for neoplasia is increased by extending the test period to 6 days. We report the first randomized comparison of 3 day with 6 day testing in asymptomatic individuals. 35,184 age and sex matched individuals were randomly allocated to receive Haemoccult over 3 or 6 days. The tests were completed by 10,176 (57.8 per cent) of the 17,616 offered 3 day Haemoccult and 9461 (53.9 per cent) of the 17,568 offered 6 day Haemoccult, a significant decrease in compliance (P less than 0.001). Of the 3 day Haemoccult tests 131 (1.29 per cent) were positive, significantly fewer than the 160 (1.69 per cent) positive tests after 6 day Haemoccult (0.01 less than P less than 0.02). Investigation of subjects with a positive test revealed 20 carcinomas (1.14 per 1000 offered and 1.97 per 1000 completing the test) in the 3 day group and 24 carcinomas (1.37 per 1000 offered and 2.54 per 1000 completing the test) after 6 day Haemoccult tests (0.5 less than P less than 0.7 for those offered the test and 0.3 less than P less than 0.5 for those completing it). After 3 day Haemoccult 112 adenomas in 76 persons were detected (4.31 per 1000 offered and 7.47 per 1000 completing the test). In the 6 day group 123 adenomas in 83 persons (4.72 per 1000 offered and 8.77 per 1000 completing the test) were detected (0.5 less than P less than 0.7 for those offered the test and 0.3 less than P less than 0.5 for those completing it). Large adenomas were found in 27 individuals after 3 day testing (1.53 per 1000 offered the test and 2.65 per 1000 completing it) and in 35 individuals after 6 day testing (1.99 per 1000 offered the test and 3.70 per 1000 completing it) (0.3 less than P less than 0.5 for those offered the test and 0.1 less than P less than 0.2 for those completing it). This study has not demonstrated a significant increase in the yield of neoplasia in asymptomatic subjects offered Haemoccult over 6 days. However there was a significant decrease in compliance and a higher rate of colonscopy in those offered 6 day testing.     

Effect of season and ambient temperature on outcome of guaiac-based faecal occult blood tests performed for colorectal cancer screening

Aim Guaiac‐based faecal occult blood tests (gFOBTs) are used in the colorectal cancer screening programme. Recent data suggested that the immunological faecal occult blood test illustrated a variation in positivity according to season and ambient temperature. Our aim was to assess the effect of season and ambient temperature on the positivity rates of the gFOBT during pilot screening for colorectal cancer. Method Data from the first year of round 1 of the pilot screening programme in Coventry and Warwickshire were analysed. Patients with positive and negative gFOBT samples were included. Patients with spoilt samples or incomplete data were excluded. Of the total of 59 513 patients, 30 311 were men and 29 202 women. Mean age was 56 years. Daily temperature data were provided by the meteorological office. Results Median exposure of the gFOBT test card was 6 days (range 1–17). Median daily maximum temperature was 14°C. Spring and summer illustrated significantly decreased positivity rates compared with autumn and winter (Pearson’s chi‐squared test, P < 0.001). Mean daily maximum temperature for the test card exposure showed no significant difference in positivity rates (P = 0.53). Subgroup analysis revealed a significant reduction in positive samples in the > 25°C subgroup (P = 0.045). Conclusions There is a seasonal variation in positivity rates of gFOBTs with increased positivity in spring and summer months. There is no difference in positivity rates in relation to ambient temperature except in subgroup analysis where there is a significant reduction in positivity rates above 25°C.     

Comparison of Coloscreen Self-Test and Haemoccult faecal occult blood tests in the detection of colorectal cancer in symptomatic patients

The usefulness of faecal occult blood tests is limited by their acceptability to patients. Standard tests require the collection of a stool sample which may inhibit compliance. Self-read tests which avoid this step have therefore been devised. Coloscreen Self-Test (CST) and Haemoccult, which may be regarded as the standard slide test, were offered to 450 consecutive patients attending surgical outpatient clinics with symptoms suggestive of lower gastrointestinal disease. Both tests were successfully completed by 383 patients. Although 262 (68 per cent) patients indicated that they preferred CST this was not reflected in the overall compliance to the two tests (CST 86 per cent, Haemoccult 90 per cent). CST gave a positive result in only eight out of 24 patients with a colorectal cancer (sensitivity = 33 per cent) compared with 13 out of 24 for Haemoccult (sensitivity = 54 per cent). CST had no advantage from increased compliance to outweigh its lower sensitivity.     

粪便隐血单克隆抗体法在检测结、直肠癌中的临床应用

目的评价粪便隐血单克隆抗体法对检测结、直肠癌的意义。方法对７８例确诊为结、直肠癌病人用单克隆抗体法和联苯胺法检测粪便隐血。结果单克隆抗体法和联苯胺法的阳性率分别为８４．６％、６１．５％（Ｐ＜０．０１）。结论单克隆抗体法检测结、直肠癌敏感性远远超过传统联苯胺法。为了提高对结直肠癌的早期诊断率,我们建议常规采用单克隆抗体法进行粪便隐血检测。     

FIT for the future: a case for risk‐based colorectal cancer screening using the faecal immunochemical test

Worldwide, the guaiac faecal occult blood test (gFOBT) is being replaced with the more accurate faecal immunochemical test (FIT) for colorectal cancer (CRC) screening. From January 2016, the National Screening Committee in the UK has recommended a change from the gFOBT to the FIT following a successful Bowel Cancer Screening Programme pilot study with over 40 000 participants. Although the test has shown improved uptake and the ability to detect significantly more colorectal cancers and advanced adenomas, the higher uptake and test positivity will challenge the capacity of colonoscopy services. One of the main advantages of the FIT is that it provides a quantitative haemoglobin concentration which has been shown to relate to the risk of CRC. Risk scoring systems which combine the FIT concentration with risk factor assessment have been shown to improve the sensitivity of the test. This individualized approach to screening could enable those at greatest risk to be referred for colonoscopy, optimizing resource use and ultimately patient outcomes.     

Survival of patients with colorectal cancer diagnosed in a randomized controlled trial of faecal occult blood screening.

BACKGROUND: Analysis of survival of subjects with colorectal cancer diagnosed by different modalities can provide insight into the mechanism by which screening has an effect. It can also give an indication of the feasibility of using prognostic indicators as surrogate outcome measures to predict mortality in future studies. METHODS: This paper examines the survival of individuals with colorectal cancer diagnosed in the Nottingham trial and explores the role of selected prognostic factors as possible surrogate outcome measures. RESULTS: Survival was significantly better in subjects with screen-detected cancers than in controls, even after adjusting for tumour stage and accounting for lead-time bias. Survival was inversely related to stage of tumour, with patients with stage A tumours having the best survival. Subjects with well or moderately differentiated tumours had a significantly better survival than those with poorly differentiated tumours. CONCLUSION: Screening for colorectal cancer by means of faecal occult blood testing improved survival among subjects with screen-detected cancers. Differences in prognostic factors largely explain the differences in survival between both non-responders and subjects with interval cancers and those in the control group, but not the improved prognosis for patients with screen-detected cancers. The use of such factors as surrogate outcome measures may therefore be inappropriate.     

Evaluation of an immunological test for occult bleeding from colorectal neoplasia

A study to determine the reliability of a recently described test, the faecal human haemoglobin test (FHH), specific for human blood, in the detection of colorectal neoplasia, is reported. All of nineteen patients with proven cancers studied were shown to have detectable blood in the stools. Three of five patients with polyps in this series also had detectable blood in the stools by this test. Although three of nineteen control subjects had positive tests, two of these were subsequently found to have bleeding sites, and the third was normal on follow up some weeks later. The findings are discussed in relation to the Hemoccult II (H-O) test results obtained in these subjects, and the implications for the possible future role for this test in screening for colorectal neoplasia.     

A population‐based audit of the clinical use of faecal occult blood testing in primary care for colorectal cancer

Aim Symptoms related to colorectal cancer (CRC) are common. We investigated the value of the faecal occult blood test (FOBT), when administered in primary care, in the diagnosis of CRC. Method All patients who underwent a FOBT (Hemoccult II) at 20 public primary care centres in Sörmland County, Sweden, during 2000–2005, were included (n = 9048). Linkage to the Swedish Cancer Registry identified all cases of CRC. Symptoms recorded at the time of the FOBT were retrieved from the patient records. The outcome from the FOBT to diagnosis and subsequent survival was compared between patients who were FOBT negative and patients who were FOBT positive. Results One‐hundred and sixty‐one patients were diagnosed with CRC within 2 years after undergoing a FOBT in primary care. These comprised 18% of all 917 patients diagnosed with CRC in the county during the study period. In 41 (25.4%) of the 161 patients the test was negative. Symptoms related to CRC were documented for 158 (98%) patients at the time the FOBT was administered. The median investigation time from the FOBT test to the diagnosis of CRC was 91 days: 80 days for FOBT‐positive patients and 188 days for FOBT‐negative patients (P < 0.001). This difference was signficant independent of age, sex and site of tumour. The hazard ratio for FOBT negativity, 3 years after the FOBT, when adjusted for age and sex, was 1.47 (95% CI, 0.81–2.68). Conclusion Despite having suggestive symptoms, 41 (4.5%) of 917 CRC patients had a negative FOBT result in primary care. This was associated with diagnostic delay and, potentially, a worse outcome.