Occult Blood Screening Research Articles

Observer variance in the reporting of faecal occult blood results using the Okokit II method.

Tests to detect blood in faeces in amounts or forms not observable on inspection (occult blood) are important in the diagnosis and treatment of lesions of the gastrointestinal tract. Faecal occult blood screening of patients has been shown to increase the detection of colorectal cancer! indeed the American Cancer Society recommends faecal occult blood tests every year for people over the age of fifty. 2 The Okokit IFM (Hughes and Hughes Ltd., Romford, Essex, UK) method used in this depart­ ment is based on the peroxidase-like activity of haemoglobin. Emergence ofa green colour within 2 min of reagent addition to the prepared faecal sample, in accordance with kit instructions, is regarded as a positive result, all other results being recorded as negative. A study was conducted to investigate the possibility of inter-observer variance in the reporting of results, without being concerned with the examination ofthe specificity and sensiti­ vity of the method. Four observers negative for red-green colour blindness were chosen from the laboratory staff. Over a period offive weeks 54samples received by the laboratory for routine faecal occult blood testing were analysed in batches of four to eight using the Okokit II kit. The test procedure was carried out on each sample by one person only, and all four observers were present. Observers simultaneously but independently recorded their results within the confines of the kit instructions. Results were classified as 'Agreement' when all four observers agreed on a result, 'Partial Dis­ agreement' when three agreed and 'Disagree­ ment' when only two agreed. It can be seen from Table I that 'Agreement' was recorded on only 57% of the samples assayed. Variation in the total results recorded as positive by individual observers was high, rang­ ing from 35% to 61%.

Flexible fiberoptic sigmoidoscopy. Important screening tool for colorectal disorders.

Because of the frequency of colorectal disease and the effectiveness of early intervention in the polyp-cancer sequence, surveillance for this problem should be a routine part of health-maintenance examinations. The general use of flexible sigmoidoscopy in conjunction with fecal occult blood screening is an extremely important part of healthcare delivery. Flexible sigmoidoscopy can easily be learned by most physicians. If use of the procedure becomes widespread, the effects of colorectal disease, in terms of both patient suffering and healthcare costs, can be reduced.

US Preventive Services Task Force. Occult blood screening for colorectal cancer

US Preventive Services Task Force. Occult blood screening for colorectal cancer

Screening for colorectal cancer: a critical review.

This article discusses the place of symptom detection, endoscopy, and fecal occult blood testing in population screening for colorectal cancer. There is now considerable evidence that screening the population over the age of 50 years for occult blood in the feces will result in an increased yield of tumors localized to the bowel at the time of surgical treatment. These tumors also have other favorable prognostic features and it is likely that the prognosis of this group will be better than the prognosis of patients presenting with symptoms in the usual way. Because of the biases that result from the selection and detection of tumors in screening studies, the mortality results of the control trials now underway must be awaited until it is known whether population screening is of real value. In chemical fecal occult blood screening tests, a compromise has to be made between sensitivity and specificity. The fecal occult blood test most widely used and the one that has been subjected to the most evaluation in screening studies is the guaiac-based slide test, Hemoccult. The predictive value of a positive test for invasive cancer is 11-17%, and for adenomas, 36-41%. This specificity is achieved at a loss of sensitivity, the interval cancer rate reported in screening studies being over 20%. Newly developed immunological techniques appear to be more sensitive and specific, but require further evaluation in population screening studies.

Rapid immunochemical detection of fecal occult blood by use of a latex-agglutination test.

A novel immunochemical test, "Hemolex," is characterized and compared with three guaiac tests: "Hemoccult" (Smith-Kline, U.S.A.), "Hemofec" (Boehringer Mannheim, F.R.G.), and "Fecatwin Sensitive" (Labsystems, Finland). We tested 191 stool specimens from patients, 144 from healthy persons. The sensitivity of Hemolex was 0.6 mL of blood per 100 g of stool. It reacts with neither animal hemoglobin nor human myoglobin, unlike the guaiac tests, nor does it react with the stool of healthy persons under no dietary restrictions, while the guaiac tests react variably. As a rule, Hemolex is insensitive to bleeding in the upper gastrointestinal tract, unlike the guaiac tests. However, Hemolex seems to be more sensitive to bleeding in the lower gastrointestinal canal than are the other tests, and we show it to be suitable for screening for occult blood originating there. It is unaffected by diet. It is simple to perform, requires no special equipment, and stool specimens, stored in the test diluent, are stable for testing for two weeks.

Posterior transsphincteric rectotomy. Indications and safety.

This study intends to make the transsphincteric approach to the rectum more well known, mainly because of the increasing number of small carcinomas and adenomas being detected by endoscopy following screening for occult blood. Thirty patients had rectotomy from 1983 to 1987. Curative surgery was performed on 15, whereas adenomas were excised in 11. Other indications were palliative excision, rectovaginal fistula, and postsurgical bleeding. Two patients had had previous transversostomies and a covering colostomy was done in one. Complications included wound infection in four and rectal fistula in four. Transversostomy became necessary in three. All colostomies were closed later and the mortality was zero. All preserved anal continence for solid and fluid feces, whereas three suffered from flatulence during a follow-up period from one to 46 months. The approach allows surgery in the upper part of the lower third of the rectum and the midrectum with a low mortality and complication rate, and should be preferred over major surgery in selected patients.

Colorectal carcinoma and Haemoccult. A study of its value in mass screening using meta-analysis.

Meta-analysis has been performed on the world literature relating to Haemoccult screening for colorectal cancer. The analysis indicated a sensitivity of about 50%, specificity of about 97%, positive predictive value of 4.3% and negative predictive value of 99.85%. These figures assume a prevalence of colorectal cancer in the population of 0.3%. A model calculation using these figures together with some additional realistic assumptions suggests no reduction in mortality compared to an unscreened population. It is concluded that many questions about faecal occult blood screening remain and that uncontrolled mass population screening is not justified at this stage.

The pros and cons of fecal occult blood testing for colorectal neoplasms.

Testing feces for occult blood is widely recommended as a means of detecting subclinical colorectal tumors. Guaiac tests such as Hemoccult are the most widely used, but chemical sensitivity is relatively low and the tests are affected by dietary peroxidases, the state of fecal hydration, and certain drugs. The newly devised HemoQuant and immunologic techniques appear more sensitive and specific, but they require further evaluation before widespread clinical usage can be recommended. Occult blood screening has both merits and weaknesses. Testing does uncover subclinical colorectal cancer, often at a relatively early stage, but whether this actually improves the prognosis remains to be proven. Benign neoplastic polyps are also detected, although it is debatable whether this is a valid rationale for screening. Test sensitivity for malignancy varies from good to moderate, but is poor for benign polyps. Specificity is usually around 97%-98%, yet the predictive value of a positive test for cancer is only about 10%; hence most test-positive individuals are needlessly subjected to invasive colonic investigations. Reported figures on public compliance with occult blood testing vary widely from excellent to poor. Published costs of screening are usually quite low, but these overlook important indirect and hidden expenses and are therefore misleading. On balance, the problems of occult blood testing currently appear to outweight the merits. This could change, however, with the newer testing techniques and with awaited mortality data from controlled clinical trials now underway.

Effect of workup strategy on the cost-effectiveness of fecal occult blood screening for colorectal cancer

Physicians respond to a positive fecal occult blood test with a variety of workup strategies. To study the effect of the choice of strategy on the net costs and health benefits of colorectal cancer screening using this test, we used a decision analysis model to compare seven strategies that physicians might choose to examine a positive “screenee.” Strategies using rigid or flexible sigmoidoscopy alone are not only insensitive, but also have high cost-effectiveness ratios. The strategy of air contrast barium enema alone had the lowest cost-effectiveness ratio. Rigid sigmoidoscopy combined with barium enema had a lower cost-effectiveness ratio than primary colonoscopy, but the strategy of primary colonoscopy could have an equal or better ratio depending on assumptions about test costs and the benefit of removing benign polyps. The primary colonoscopy strategy is both more effective and less costly than the combination of flexible sigmoidoscopy and barium enema. The optimal strategy will vary with local factors, and with the perspective of the decision-maker.

Influence of non-steroidal anti-inflammatory drugs on the outcome of faecal occult blood tests in screening for colorectal cancer.

Non-steroidal anti-inflammatory drugs have been accused of causing false positive results in faecal occult blood tests for colorectal cancer. A study was therefore performed in 10,931 people undergoing faecal occult blood screening tests to assess the effect of these drugs on the predictive value of a positive test result. Those with a positive result were interviewed and a full drug history was taken before they underwent a full colorectal examination. Of the 455 people with a positive result, 50 were taking non-steroidal anti-inflammatory drugs: 10 (20%) had colonic neoplasia. Of the 405 who were not taking non-steroidal anti-inflammatory drugs, 129 (32%) had colonic neoplasia. These detection rates were not significantly different, and the predictive value of a positive result for an adenoma larger than 1 cm was 14% in the group not taking anti-inflammatory drugs and 26% in the group taking them (not significant). These results suggest that a finding of occult faecal blood cannot be attributed to upper gastrointestinal tract bleeding caused by non-steroidal anti-inflammatory drugs and should be followed by a thorough colorectal examination.

An Evaluation of Fecal Occult Blood Screening in Automated Multiphasic Health Testing and Services

In the present paper, the efficacy of fecal occult blood screening in automated multiphasic health testing and services (AMHTS) is evaluated, and some problems with it are also discussed. A total of 54,735 subjects were screened for occult blood by the Shionogi slide 1-day method. According to a follow-up survey of the 715 subjects judged (+ +), 42 cases of colorectal polyp and 13 of colorectal cancer were confirmed. Eight of the 12 cases of primary colorectal cancer, excluding a case of metastatic transverse colon cancer, were located in the colon's right-side. The result may have arisen from the fact that most subjects in AMHTS are relatively young and free of symptoms. This suggests that fecal occult blood testing in AMHTS may be useful for detecting colon cancers of the right side as well as of the left. Of the nine cases of primary colorectal cancer previously screened, five had been judged (+) in previous testing. This fact indicates an especially rigorous examination of subjects judge (+) to be necessary in AMHTS. Meanwhile, of the 45 cases of gastric cancer detected by enhanced X-ray testing, only eight (17.8%) subjects were judged (+) or (+ +). It is suggested that fecal occult blood testing may not, therefore, be too effective in screening for gastric cancer.

Participation in fecal occult blood screening: A critical review

The factors that influence participation in fecal occult blood screening for colorectal cancer are poorly understood. A better understanding of these factors could lead to better screening products or to educational approaches to increase participation with currently available products. In this article, we review findings from studies that have examined the determinants of participation in fecal occult blood screening. Two components of participation are identified: initial agreement to participate and subsequent compliance with the testing procedures. We conclude that the factors that lead to agreement often differ from those that lead to compliance. Following the literature review, we discuss ways in which recent advances in attitude and behavior research might be used to improve future investigations of the determinants of participation in fecal occult blood screening. Specifically, this research suggests that investigators should focus on beliefs and attitudes associated with the perceived consequences of screening participation rather than on other types of beliefs and attitudes; measure beliefs and attitudes at the same level of specificity as behavior; and distinguish between individuals' initial agreement to participate in screening and their actual participation.

Faecal occult blood screening of first degree relatives of patients with colorectal cancer.

A full first-degree family history was taken from 161 patients with colorectal cancer (Group 1) and from a group of 203 subjects previously investigated and found to have no colorectal neoplasia (Group 2). Twenty-six (16%) of patients in Group 1 compared with 23 (11%) in Group 2 had at least 1 first-degree relative with colorectal cancer (p = 0.23). Contact of first-degree relatives was possible in 123 patients in Group 1. Of these, 4 were members of 'cancer families' with 26 available first-degree relatives. The remaining 119 patients had 341 contactable first-degree relatives. They were approached by post and offered faecal occult blood (FOB) screening. One hundred and sixty-two (47%) completed FOB tests of which 12 (8%) were positive. Investigation of these individuals detected 4 adenomas. In the subgroup of 20 patients with 1 or 2 first-degree relatives with colorectal cancer, there were 78 potential relatives of whom 71 were contacted. Thirty-two (45%) FOB tests yielded 1 positive found to have an adenoma. A control group of 332 individuals was selected randomly from general practitioners' lists and offered FOB testing. One hundred and fifty-five (47%) complied of whom 7 (4.5%) were positive. Investigation yielded 1 adenoma. Thirteen of the 26 relatives of the 4 'cancer family' patients were investigated by endoscopy and 2 (15%) had large polyps detected. Although there may be an increased risk of colorectal neoplasia in first-degree relatives of patients with sporadic colorectal cancer, this risk is not sufficiently high to justify separate screening.

Prevention of cancer of the colon--a review of faecal occult blood screening.

Prevention of cancer of the colon--a review of faecal occult blood screening.

Acceptability of a faecal occult blood screening protocol for carcinoma of the colon in family practice.

Cancer of the colon is the second most common malignancy in North America and screening methods are needed for diagnosing the lesions at an early stage. Faecal occult blood screening is a method of secondary prevention which is particularly adaptable to the family practice setting. In order to test the feasibility of using this test in family practice, 16 family physicians participated in a trial screening programme using the Hemoccult II test. During the two-month trial 776 patients over 40 years of age were screened; 19 of the tests were positive but in two cases patients were thought to have failed to follow dietary and medical restrictions. Of the 17 patients with verified positive tests, further investigation showed five patients had neoplastic disease and three of these had malignant disease. The detection rate for cancer of the colon using the Hemoccult II test was therefore 3/776, equivalent to 3.9 per 1000 cases screened. By narrowing the age range for screening patients to between 45 and 75 years, the time involved to screen the population at risk could be decreased.

Occult-Blood Screening for Colorectal Carcinoma: The Yield and the Costs

The potential benefits and risks associated with Hemoccult screening have been reviewed in two companion papers. This final article assesses two major determinants of the overall "disease yield" of occult-blood screening, as well as the economic costs entailed by the maneuver. First, asymptomatic polyps detected and treated by such screening are more properly considered "false" positives than "true" positives--the benefits of their aggressive diagnosis and extirpation in the general population being much less established than the risks. Secondly, the ongoing detection rate for colorectal carcinoma on subsequent (e.g., annual) screenings of a population already screened will be substantially less than the initial screening yield; yet, the risks of confirmatory diagnostic procedures remain high. Lastly, there are many hidden costs to occult-blood screening that have generally not been recognized. Therefore, the use of Hemoccult screening as a routine health maintenance maneuver cannot yet be justified for any age-group.

Occult-Blood Screening for Colorectal Carcinoma: The Risks

The evidence that occult-blood (Hemoccult) screening for colorectal carcinoma is beneficial has been examined in a companion paper. No data have yet been published demonstrating actual reductions in morbidity or mortality among patients undergoing the test. In this paper the risks of occult-blood screening are examined. It is shown that significant harm may result from the test's widespread application, due to the need for extensive endoscopic and radiological investigations in persons with a positive result (the vast majority of whom will subsequently be found not to have cancer). Furthermore, the most favorable benefit-risk ratio in Hemoccult screening (i.e., the highest positive predictive value for cancer) is found among persons over 70 years of age. Yet they are generally the least likely of patients screened to undergo treatment if a cancer is found. It is concluded that the risks of occult-blood screening could outweigh the benefits of any age group.

Occult-Blood Screening for Colorectal Carcinoma: The Benefits

Preventive medical interventions directed at the general population require rigorous evaluation of the associated benefits, risks, and costs. This paper, the first of a three-part series, assesses the current evidence for the effectiveness of occult-blood (Hemoccult) screening for colorectal carcinoma. When judged by explicit methodologic criteria for the effectiveness of screening, that evidence demonstrates no clearcut benefits to patients found to have colorectal cancer through testing for occult blood. In contrast, there may be substantial risks and costs associated with the widespread use of this preventive maneuver. These are considered in two companion papers.

Recruitment of subjects for fecal occult blood screening: a comparison of two methods in Jerusalem.

Two approaches to the recruitment of subjects for screening for fecal occult blood were tested in two middle-class neighborhoods in Jerusalem. After invitations were mailed to 2,909 persons aged 40 and older, 855 (29%) requested the special "Colo-Screen" packet of slides; and 496, one-sixth of those contacted originally, ultimately returned stool specimens for examination. In a parallel campaign by family doctors, invitations were distributed personally to 324 patients visiting a Sick Fund Clinic; 225 (69%) requested Colo-Screen slides and 137 (42% of the persons invited) sent in stool specimens. Males and females responded equally. Of the 633 specimens received, 29 (4.6%) were positive for occult blood; two cancers and seven adenomatous polyps were found and resected. Screening programs for colorectal cancer should encourage greater personal participation of family doctors in the recruitment process.

Screening for occult blood in selected patients. The potential for false-negatives.

Seventy-one patients presenting for elective hernia repair without gastrointestinal symptoms were screened for occult blood in their stools. All patients had stools negative for occult blood and were studied with proctosigmoidoscopy and barium enema. Polyps were found in 10% of the study population. The potential for missing polyps definitely exists if patients are selected for further studies only on the basis of tests for occult stool blood.