Screening for colorectal cancer with immunochemical faecal occult blood tests

Population-based studies have shown that guaiac faecal occult blood testing followed by colonoscopy in case of positivity can reduce colorectal cancer mortality. However these tests have been criticised for their fairly low sensitivity. For this reason attention has been given to alternative tests. The aim of this paper is to review the evidence for screening for colorectal cancer using qualitative immunochemical faecal occult blood tests. For the complete range of tested cut-off values, immunochemical faecal occult blood tests lead to higher diagnostic yield, improved sensitivity and greater participation. The optimal number of samples and the optimal cut-off value has to suit local resources and the acceptability of missed cancers. All economic evaluations, despite some differences between studies, add further arguments to support the opinion that the immunochemical faecal occult blood test is currently the most cost-effective screening test for average-risk populations. These economic evaluations provide strong arguments in favour of the 1-sample strategy. With decreasing the cut-off value similar performances can be achieved with one-compared to two day sampling. Too few data are currently available to accurately compare existing qualitative tests.     

Controlled trial of faecal occult blood testing in the detection of colorectal cancer

20 525 patients from general practitioners' lists were randomly allocated into test and control groups. The 10 253 test subjects were invited to perform haemoccult faecal occult blood testing over 3 days. 3613 (36 . 8%) of the 9807 who received their invitations completed the test. Compliance was improved by direct invitation from the general practitioner and by prior health education by letter or interview. 77 people (2 . 1%) had a positive test result, and 50% of these on investigation had neoplastic disease--12 had invasive carcinomas (9 Dukes' stage A, 2 stage B, 1 stage C) and 27 had 40 adenomas (12 over 2 cm, 2 of which contained areas of severe dysplasia). In the year following the screening test 1 carcinoma (stage C) has presented in the group which accepted the test, and 10 carcinomas (4 stage B, 4 stage C, 2 stage D) have presented in the control group. This respresents a 3 . 6 times greater detection rate per 1000 persons in the test group than in the control group. Only 8 adenomas have presented in the control and non-responding groups. Fibreoptic sigmoidoscopy identified the 10 carcinomas within its range and 39 of the 40 adenomas. Double-contrast barium enema identified only 9 of the 12 carcinomas and 24 (62%) of the 40 adenomas. All 3 carcinomas not identified by barium enema were polypoid Dukes' stage-A lesions.     

Faecal calprotectin and faecal occult blood tests in the diagnosis of colorectal carcinoma and adenoma

BACKGROUND AND AIMS: Testing for faecal occult blood has become an accepted technique of non-invasive screening for colorectal neoplasia but lack of sensitivity remains a problem. The aim of this study was to compare the sensitivity and specificity of faecal calprotectin and faecal occult blood in patients with colorectal cancer and colonic polyps. METHODS: Faecal calprotectin and occult blood were assessed in 62 patients with colorectal carcinoma and 233 patients referred for colonoscopy. The range of normality for faecal calprotectin (0.5-10.5 mg/l) was determined from 96 healthy subjects. RESULTS: Median faecal calprotectin concentration in the 62 patients with colorectal carcinoma (101 mg/l, 95% confidence interval (CI) 57-133) differed significantly from normal (2.3 mg/l, 95% CI 1.6-5.0) with 90% of patients having elevated levels (normal <10 mg/l) whereas only 36/62 (58%) had positive faecal occult bloods. There was no significant difference in faecal calprotectin levels when considering location or Dukes' staging of tumour. Percentage positivity of faecal occult bloods was significantly higher for Dukes' stage C and D cancers compared with Dukes' A and B. In the colonoscopy group, 29 patients with adenomatous polyps were detected in whom the median faecal calprotectin was 12 mg/l (95% CI 2.9-32). Sensitivity for detection of adenomatous polyps was 55% using the calprotectin method and 10% using faecal occult blood testing. The overall sensitivity and specificity of calprotectin for colorectal cancer and adenomatous polyps as a combined group was 79% and 72%, respectively, compared with a sensitivity and specificity of faecal occult blood of 43% and 92%. CONCLUSIONS: Faecal calprotectin is a simple and sensitive non-invasive marker of colorectal cancer and adenomatous polyps. It is more sensitive than faecal occult blood tests for detection of colorectal neoplasia at the cost of a somewhat lower specificity.     

Rehydration of guaiac-based faecal occult blood tests in mass screening for colorectal cancer. An economic perspective

Owing to dehydration during storage, faecal occult blood tests have been found to lose sensitivity; accordingly, test rehydration before development has been advocated, although this practice has yet to be subjected to an economic evaluation. In this paper, the results from two major screening trials in Sweden and England, one using rehydration and the other not, are so evaluated, based on a costing model developed within the English trial. The higher sensitivity resulting from rehydration was found to be accompanied by losses in specificity, such that, although more cancers are detected, the costs of screening and of cancer detection are actually considerably higher under the rehydration regimen than with non-hydration.     

Diagnostic accuracy of immunochemical versus guaiac faecal occult blood tests for colorectal cancer screening

Background  

Immunochemical tests show important advantages over chemical-based faecal occult blood tests (FOBT) for colorectal cancer (CRC) screening, but comparison studies are limited. This study was performed to compare the accuracy of a sensitive immunochemical test with the guaiac test for detecting significant neoplasia (advanced adenomas and CRC) in an average-risk population.     

Colonoscopic evaluation of immunochemical fecal occult blood test for detection of colorectal neoplasia

BACKGROUND/AIMS: This study was carried out to assess the validity of three testing methods of immunochemical occult blood according to the number of collection times as a means for colorectal cancer screening. METHODOLOGY: Four thousand six hundred and eleven asymptomatic individuals, who received both an immunochemical occult blood test with a three-day method and colonoscopy during a medical checkup, served as subjects for this study. For evaluation of the desirable number of sampling times, we used the results of the first day for the 1-day method, the results of the first and second days for the 2-day method, and the results of three-consecutive days for the 3-day method. Sensitivities and specificities of these three testing methods were evaluated. RESULTS: Sensitivities and specificities for colorectal cancer were calculated to be 56% and 97% for the 1-day method, 83% and 96% for the 2-day method, and 89% and 94% for the 3-day method, respectively, showing a significant difference in sensitivity between the 1-day and the 2-day methods, as well as the 3-day method (p < 0.01), and in specificity between the 1-day as well as the 2-day and 3-day methods (p < 0.05). CONCLUSIONS: These findings indicate that the immunochemical fecal occult blood test is useful for the diagnosis of colorectal cancer, and that 2-day testing is recommended as a means of screening for colorectal cancer.     

Guaiac tests for detection of occult faecal blood loss in patients with endoscopically verified colonic polyps

To evaluate the sensitivity of guaiac tests for colonic polyps, two tests were made on occult blood in faeces--Hemoccult II and Fecatwin-S--from 625 and 549 patients, respectively, referred for colonoscopy. Polyps were found in 212 and 194 patients, and these had one or more tests positive in 41% (Hemoccult II) and 48% (Fecatwin-S). The incidence of positive tests was greater for polyps situated in the transverse, descending, and sigmoid colon; for polyps with a stalk, villous elements, and dysplasia; and especially for large polyps. Although size was the most important factor for the bleeding tendency, at least one third of patients with polyps over 10 mm in diameter had no positive guaiac reactions. In patients at high risk of developing polyps, therefore, these tests cannot replace, but may well be supplementary to, radiography with double-contrast technique and colonoscopy.     

粪便转铁蛋白和免疫粪隐血试验在结直肠癌筛查中效能的比较

目的评估粪便转铁蛋白(TF)和免疫粪隐血试验(IFOBT)在筛查结直肠癌中的效能。方法筛查对象为1 943例无症状受试者。收集1次粪便标本,同时用于TF和IFOBT检测。两者任一结果为阳性,即通知受试者行结肠镜检查。分别计算TF、IF-OBT和两者联合检测的性能指标。结果共有1 737例受试者接受TF和IFOBT检查,其中251例(14.5%)至少1项结果为阳性。共有193例接受结肠镜检查,共发现3例结直肠癌和43例进展期腺瘤。与单独使用IFOBT相比,TF和IFOBT联合检测(并联)明显提高了结直肠癌和进展期腺瘤的检出率(2.6%vs 1.6%,P=0.034)。结论 TF和IFOBT联合检测能提高筛查时结直肠癌和进展期腺瘤的检出率。     

Effect of faecal occult blood testing on colorectal cancer mortality in the surveillance of subjects at moderate risk of colorectal neoplasia: a case-control study

Colonoscopy is the established method of surveillance of subjects at high risk of developing colorectal neoplasia. Its role in the surveillance of a population at moderate risk is less clear, however, as the procedure is expensive, time consuming and occasionally hazardous. The aim of this study was to estimate by case-control methods the effect of faecal occult blood (FOB) screening on colorectal cancer (CRC) mortality in a population at moderate risk of developing CRC. Screening by FOB testing prior to diagnosis in patients over the age of 45 years who died of CRC diagnosed in 1989-1998 was compared with screening in controls matched with the case for age and sex. Information about episodes of FOB testing and potential confounders was obtained from the data collection system of the screening programme. Cases were less likely than controls to have ever been screened, with an odds ratio of 0.64 (95% confidence interval 0.34-1.15) for exposure to at least one FOB testing. There was no significant difference between the sub-groups according to gender, age at diagnosis or location of the cancer. The inverse association between screening for faecal occult blood and fatal colorectal cancer suggests that screening in a population at moderate risk of CRC can reduce mortality from CRC in this group.     

Screening of colorectal tumours using an improved faecal occult blood test. Quantitative aspects.

A recently developed double test for detecting faecal occult blood (a sensitive guaiac test combined with a quantitative immunological human haemoglobin test), was adapted to population screening. The study involved an unselected population of 10,343, aged 49-74 years. There was 66.5% participation. 174 colonoscopies were done, yielding seven adenocarcinomas, 44 adenomas and four hyperplastic polyps. By eliminating benign anal tract bleeding, the number of endoscopies decreased from 340 to 174. Most tumours showed an absorbance over 0.80, and it is suggested that by setting the lower limit of positivity at the 0.80 absorbance level, the number of clinical examinations could fall to about 1%, without substantially missing tumours.     

Immunological fecal occult blood test vs. serum ferritin for detection of colorectal neoplasia in high risk asymptomatic population

Introduction: Fecal occult blood tests (FOBT) (biochemical or immunological) are based on the fact that most of the polyps or cancers bleed. Anemia due to iron deficiency is a wellknown sign for colorectal cancer (CRC). Ferritin is frequently used to select candidates for colonoscopy. Objective: To determine and compare the diagnostic value of immunological fecal occult blood test vs. ferritin for the detection of colorectal neoplasia (cancer or polyps) in high-risk patients. Methods: A transversal prospective study at National Cancer Institute, Mexico City, in consecutive asymptomatic subjects at high risk for CRC was performed, comparing two tests (immunological against serum ferritin) with colonoscopy plus histopathology. Both tests were performed in a blindly fashion previous to colonoscopy. Results: Fifty patients were included in the study; twenty-eight patients had colorectal neoplasia (21 CRC, 7 adenomas). All immunologic tests for fecaloccult blood were positive in patients with colorectal lesions (sensitivity, 98%). There was no difference between the mean ferritin levels in patients with CRC or adenomas vs. those with negative colonoscopy (p = 0.58). The cutoff point where significant relationship between serum ferritin levels and colon lesions was established was ?46 ng/mL. In anemic patients with serum ferritin levels <46 ng/mL, the test had a sensitivity 53%, specificity 86%, positive predictive value 83%, and negative predictive value of 59% (p = 0.003). Conclusions: The immunological FOBT is a better diagnostic tool than serum ferritin for screening of colonic neoplasms.