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PubMedDate not supplied

[[Evaluation of various methods of studying fecal occult blood].

Occult blood testing for detection of asymptomatic colorectal cancer is an old concept. The authors review the literature about the screening value of current tests. Among the chemical tests, Hemoccult is the most popular and the best studied. Sensitivity and specificity are moderate. False negative reactions are due either to the test itself (high level of sensitivity, loss of reactivity) or to the tumour (intermittent or insufficient bleeding, localization etc...). False positive reactions are due to the interference of a high peroxidase diet. The Hemoccult test is nevertheless interesting because it is simple, cheap and well accepted. Detected cancers tend to be at a relatively early stage: 60 to 80% of Dukes A or B. New methods--Hemoquant and immunochemical methods--are being developed. Their high degree of sensitivity and specificity for human hemoglobin makes them too complex and too costly. Whatever the efficacity of a test to detect occult blood may be, we must know whether the screening of an asymptomatic population could decrease the mortality rate of colorectal cancer, before using it on a large scale. Only long-term controlled trials can give us an answer in the future.

Colorectal Neoplasms↗
PubMed1984

[Screening for colo-rectal neoplasms by the study of fecal occult blood].

Occult blood testing has been proposed as a screening tool for colorectal cancer. At the present time guaiac testing is considered the most suitable for mass screening. The specificity of the test is affected by diet. For this reason it is necessary to adhere to a meat-free diet while the necessity of eliminating peroxidase containing foods as uncooked vegetables and fruit is controversial. The sensitivity of guaiac test is affected by the intermittence of colorectal cancer bleeding, by the quantity of ascorbic acid and fibers in the diet and by the development modality of the test. The experience of the authors is based on a screening protocol applied on some populations in the province of Florence (Italy). The protocol is based on guaiac test and an anamnestic selection of high-risk patients. 6029 patients have performed guaiac test. In 1159 patients, the results of occult blood testing and sigmoidoscopy have been compared. This analysis accounts for a predictive value of 50%, a specificity of 95.6%, and a sensitivity of 68% for carcinomas and 21.3% for adenomas. In conclusion, guaiac testing seems to warrant a good cost/benefit ratio but because its sensitivity is too low, it is necessary to include other selective tools (the anamnestic questionnaire) as well as an over-all major effort in the research of more sensitive ways of testing.

Colonic Neoplasms↗
PubMed1999

Detection of upper gastrointestinal blood with fecal occult blood tests.

OBJECTIVE: Although fecal occult blood (FOB) tests have most often been used to detect occult bleeding from the lower gastrointestinal (GI) tract, their utility in detecting occult blood loss from the upper GI tract is less well understood. The aims of this study were to determine whether small amounts of blood from the upper GI tract can be detected by currently available FOB tests and, if so, to correlate FOB tests with semiquantitative GI blood. METHODS: Groups of 10 healthy volunteers without a history of GI disease drank 5, 10, or 20 ml of their own blood mixed with tomato juice for 5 or 3 consecutive days. Standard dietary and medication restrictions were observed. Consecutive stools were tested for 2 days before, as well as 4 days after, blood ingestion. Each stool was simultaneously tested for FOB with HemoQuant (HQ), Hemoccult II (HO II), Hemoccult II SENSA (SENSA), HemeSelect (HS), and FlexSure OBT (FS). RESULTS: The mean age and hemoglobin concentration of the study population were 29.3+/-0.5 yr and 14.3+/-0.3 g/dl, respectively. No subject noted GI symptoms during blood ingestion. Fecal blood levels (measured by HQ) were elevated within 2 days after initiation of blood ingestion and remained elevated until 2-3 days after cessation of blood ingestion. Mean fecal blood levels peaked at 2.1, 7.9, 8.0, and 13.5 (mg hemoglobin/g stool) in groups ingesting 5 ml/5 days, 10 ml/3 days, 10 ml/5 days, and 20 ml/3 days, respectively. The proportion of positive tests during and immediately after the period of blood ingestion was greatest in the 20 ml/3 day group; 16% of HO II samples were positive as were 64% of SENSA and 67% of HQ samples. SENSA was more sensitive than HO II in all blood ingestion groups. At least one positive SENSA test was present in 50% of subjects ingesting 10 ml of blood (each 3 and 5 day groups) and in all subjects ingesting 20 ml/day. Immunochemical tests did not detect upper GI blood in any blood ingestion group. CONCLUSION: Inasmuch as many upper GI tract lesions have been reported to bleed small quantities of blood such as that studied here, and this amount of blood is readily detected with widely used guaiac-based FOB tests including Hemoccult II SENSA, the data emphasize that caution is warranted before attributing positive guaiac tests only to sites in the lower GI tract. The data raise the possibility that a combination of a highly sensitive guaiac-based FOB test plus an immunochemical could help differentiate occult upper from lower GI bleeding.

Adult↗
PubMed1998

A study of laboratory based faecal occult blood testing in Melbourne, Australia. The Faecal Occult Blood Testing Study Group.

Faecal occult blood tests (FOBT) are widely used in clinical practice and are under increasing scrutiny as a tool for colorectal cancer screening. However, there is little information regarding the quality of testing performed in pathology laboratories. Therefore, we asked 13 pathology laboratories in Melbourne, Australia, to test coded contrived faecal samples prepared from a composite stool specimen which had been spiked to various concentrations of haemoglobin. The samples were provided to the laboratories in two forms: (i) on/in the sample collection device appropriate for the faecal occult blood test they normally used; and (ii) as a moist faecal sample. Some variation in threshold analytical sensitivity between laboratories for the same FOBT was observed for Hemoccult SENSA, ColoRectal, Hematest, MonoHaem and Hemolex suggesting that, at least for those tests, technician training could be improved. Two tests, Hematest and an in-house FOBT did not perform as well as the other FOBT. When samples were sent in moist form, Hemoccult SENSA (P = 0.0002), ColoRectal (P = 0.02) and MonoHaem (P = 0.04) had significantly lower overall positivity rates; for Hemolex the decrease was not significant (P = 0.3). The lower positivity rate with moist samples is important, given that 11 of the 13 laboratories in the study stated that they receive at least some samples in moist form. Thus, technician training and laboratory procedure need to be reviewed to maximize the benefits of faecal occult blood testing in clinical practice, especially with its expanding role in colorectal cancer screening.

Australia↗
PubMed1999

Fecal occult blood tests in occult gastrointestinal bleeding.

Occult gastrointestinal bleeding is diagnosed by using one of the commercially available fecal occult blood tests (FOBTs). Guaiac-based slide tests are most frequently used, although the more specific immunochemical methods are promising. The guaiac tests are inexpensive, nonspecific, qualitative measures of stool blood, and their use requires dietary and drug restrictions. Clinicians need to be aware of the causes of false-positive and false-negative test results. Although specific for the presence of human blood, immunochemical tests are more expensive and tend to react also to physiological quantities of blood in fecal specimens. Whichever test is chosen, it must be processed and read correctly. Annual FOBT screening for colorectal cancer, combined with periodic flexible sigmoidoscopy, is a cost-effective method of detecting early, curable colorectal cancer.

Adenocarcinoma↗
PubMed1993

Does use of the Coloscreen Self-Test improve patient compliance with fecal occult blood screening?

Occult blood-screening methods which do not require stool manipulation have been devised in an attempt to improve patient compliance with fecal occult blood testing. We performed a randomized, prospective study comparing patient compliance with the Coloscreen Self Test, a fecal occult blood detection method which does not require stool manipulation, and standard guaiac-impregnated cards in a VA clinic and a university-based private practice to determine whether the Coloscreen Self-Test would improve patient compliance with fecal occult blood testing. Overall, there was no significant difference in compliance between the two tests, with a compliance of 71% (105/147) for the guaiac cards and 60% (88/136) for the Coloscreen Self-Test (p = 0.49). However, multiple logistic regression showed that, when using the Coloscreen Self-Test, patients at the VA clinic had significantly reduced compliance. Only 46% (23/50) returned the Coloscreen Self-Test compared with 84% (42/50) who returned the guaiac cards (p < 0.05). We conclude that the Coloscreen Self-Test does not improve patient compliance with fecal occult blood testing, and may reduce compliance in some sectors of the population.

Colorectal Neoplasms↗
PubMed1995

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.

Age Factors↗
PubMed2000

Effectiveness and economic impact of screening for colorectal cancer by mass fecal occult blood testing.

OBJECTIVES: Fecal occult blood testing has been shown to reduce mortality from colorectal cancer in large randomized, controlled trials conducted in the United States, Denmark, and the United Kingdom, and mathematical simulation modeling found it to be cost-effective relative to other health care services. Before making a concerted effort to implement mass fecal occult blood testing based on this evidence alone, however, we considered it prudent to critically re-evaluate the effectiveness and economic impact of screening in the US population as a whole. METHODS: To assess the effectiveness of screening, we projected published outcomes from each of the three large randomized controlled trials of fecal occult blood testing to the US population, as if each clinical trial had been done in the population as a whole. We then determined the resource costs of detection and treatment that would be associated with the outcomes predicted from each trial. RESULTS: More than 1 million colorectal cancers could be expected to arise over 10 yr in the cohort of US residents eligible to enter a screening program in 1997, and trial outcomes indicate that > or = 60% of these cancers would be fatal. If the 60-67% compliance rate of the population-based randomized controlled trials were achieved, a fecal occult blood testing program would detect 30% of known colorectal cancers and save 100,000 lives over 10 yr. Screening would incur total costs of $3-4 billion over 10 yr, or $2,500 per life-year saved. CONCLUSIONS: Mass fecal occult blood testing is cost-effective, and, although not inexpensive, many would consider the total cost acceptable. Even with a concerted effort to achieve compliance, however, the effectiveness of fecal occult blood testing would be limited to saving the lives of < or = 15% of those who otherwise would die from their cancer in the first 10 yr after beginning mass screening. The limitations of fecal occult blood testing suggest the need to further evaluate the role of endoscopy in screening, and to develop more effective, noninvasive screening tools.

Aged↗
PubMed1982

Bleeding patterns in colorectal cancer: the effect of aspirin and the implications for faecal occult blood testing.

Faecal occult blood testing for 3 consecutive days is recommended for the detection of colorectal cancer. Is this adequate? Haemoccult tests were performed for 6 days on the faeces of 50 patients with colorectal cancer. Enteric-coated aspirin was given during the final 3 days to see if its systemic effect on coagulation would increase tumour bleeding. In 25 patients blood loss was quantified by radiochromium assay. Bleeding was slight and intermittent with large daily fluctuations in individual patients. Median daily loss before aspirin was 1.2 ml and after aspirin 2.5 ml. Thirty per cent of the tumours were Haemoccult negative using the standard 3-day regimen and 18 per cent were negative after aspirin. Over the 6-day period, 10 per cent were persistently negative. We conclude that new methods are required to improve the diagnostic yield from faecal occult blood tests.

Aspirin↗
PubMed2002

A new immunological test strip device for the rapid, qualitative detection of faecal occult blood.

OBJECTIVE: Guaiac tests for faecal occult blood are still the most commonly performed screening procedure for colorectal cancer. Because both sensitivity and specificity of faecal occult blood testing are critical to cost-effective colorectal cancer screening programs, we investigated a rapid immunological test strip device for bedside detection of faecal occult blood. METHODS: Stool specimen from 100 patients were chosen for this study based on the presence (n = 50) or absence (n = 50) of faecal occult blood as measured with a human haemoglobin ELISA (cut-off level </= 10 micro g Hb/g stool). All specimens were analysed for faecal occult blood by a guaiac test (Hemocare) and an immunological test strip device (Prevent ID CC). RESULTS: Sensitivity and specificity of the immunological faecal occult blood test strip device were 76 % and 92 %, compared to 30 % and 90 % for the guaiac test. Increasing the cut-off level of the haemoglobin ELISA to </= 20 micro g Hb/g stool, the corresponding sensitivity and specificity were 86 % and 83 % for the immunological test strip device and 42 % and 92 % for the guaiac faecal occult blood test, respectively. The highest positive predictive value was achieved with the immunological test strip device. CONCLUSIONS: The new immunological test strip device is more sensitive than a guaiac test for the detection of faecal occult blood, whereas the specificity of both tests was comparable. However, the clinical validity of this new immunological faecal occult blood test strip device for colorectal cancer screening has to be established, yet.

Colorectal Neoplasms↗
PubMed1987

[Comparison of chemical and immunological methods in fecal occult blood testing].

Conventional occult blood testing using the chemical method has been compared with newly developed immunological testing methods; the Hemoccult slide II (HEM II) test has been widely accepted as a guaiac test but such recent tests as the Latex agglutination test (Latex) and the Enzyme Immunoassay method (EIA) have also come to be employed. Thirty colorectal cancer patients, 30 gastric cancer patients and 30 healthy persons were subjected the three above described tests during 3 consecutive days while under no restricted diet. False positive rates during this three-day testing period were 26.7% in HEM II, 93.3 in Late and 8.3% in EIA. Although the immunological testing method has the advantage of reducing the false positive rate without the need for a restricted diet it is time-consuming and expensive. Considering these results as well as our previous knowledge accrued from a mass survey, it is suggested that a new flow-chart may be found necessary, in which an initial screening is given by the chemical method and then followed by a secondary screening by the immunological method. This new flow-chart, if routinely employed, would greatly facilitate the mass screening of colorectal cancer.

Hemoglobins↗
PubMed1998

Fecal occult blood testing: clinical value and limitations.

Occult blood in the stool can be detected by chemical (guaiac), heme-porphyrin, or immunological methods. Each has advantages and disadvantages, with the guaiac slide test Hemoccult II (SmithKline Diagnostics) remaining the most widely used. Various technical factors affect its clinical performance, most notably whether the slides are rehydrated before processing; hydration increases test sensitivity for colorectal cancer but markedly decreases specificity, resulting in a large number of false-positive reactions that require invasive and expensive colonic workup. Newer immunological tests generally have high sensitivity, but poor specificity remains an important problem. In clinical screening situations, unhydrated Hemoccult has about 50% sensitivity for colorectal cancers and about 98% specificity. Only 5% to 10% of positive reactions prove due to cancer, however, so the large majority of reactive tests are false positives; this is an important weakness of occult blood screening. Slide hydration detects more tumors, but the predictive value of a positive test for cancer drops to only about 2%, which greatly diminishes the appeal of hydration. Sensitivity of occult blood tests for benign colonic polyps is poor, and most polyps found during workup of a positive reaction are actually detected by chance because of high prevalence in the general population. Controlled clinical trials have now documented that periodic occult blood screening produces a relatively small but significant mortality benefit from colorectal cancer--about 15% to 18% for biennial testing with unhydrated Hemoccult. Aggressive annual screening with hydrated Hemoccult may lower mortality by more than 30% but at a very high cost because of poor specificity and very low predictive value. Regular occult blood testing beginning at age 50 has been endorsed by many professional organizations because of the documented mortality benefit, but poor compliance, high costs, and ethical uncertainties seriously temper its justification. Whether to implement widespread occult blood screening remains a difficult societal decision.

Colorectal Neoplasms↗
PubMed1987

Screening for colorectal neoplasms. A comparison of the fecal occult blood test and endoscopic examination.

Testing for occult blood in stool is used frequently as a screening technique for colorectal carcinomas, but no study has ever shown an improved survival rate for colorectal carcinoma in patients screened by this method. Consequently, the authors have prospectively compared the sensitivity of endoscopy and occult blood testing in finding colorectal neoplasms. During the first year of the Surgical Endoscopy Service, 585 patients underwent sigmoidoscopy or colonoscopy. Seventy-nine patients (13.5 percent) were excluded from the study because their occult blood status was not recorded. Patients averaged 63 + 10 years of age and 98 percent were men. Of the 348 patients with occult blood negative stools 55.5 percent underwent colonoscopy and 44.5 percent underwent sigmoidoscopy. Polyps were found in 25.6 percent of these patients, colorectal carcinomas in 2.6 percent, and diverticulosis 36.2 percent. Of the 158 patients with occult blood positive stool, 76.5 percent underwent colonoscopy and 23.4 percent underwent sigmoidoscopy. Polyps were discovered in 39.0 percent of these patients, colorectal carcinomas in 10.1 percent, and diverticulosis in 43.0 percent. Thus, the occult blood test was negative in 59 percent of patients with polyps and 36 percent with colorectal cancers. These data indicate that lower gastrointestinal endoscopy is superior to occult blood testing in detecting colorectal neoplasms. These results further suggest that using the occult blood test as a screening test for colorectal neoplasms will result in a significant number of these lesions being missed at an early curable stage.

Aged↗
PubMed1979

A diagnostic approach to occult blood in the stool.

Occult blood in the stool may be the first sign of otherwise asymptomatic colorectal cancer or other gastrointestinal disease. All patients over 40 should therefore have a rectal examination that includes a Hemoccult slide test. A rational diagnostic plan is essential to identify the source of occult blood in the stool. Most gastrointestinal cancer is operable if diagnosed early, so early detection of these lesions is imperative.

Aged↗
PubMed1987

Dietary restrictions and fecal occult blood testing.

"Unprepped" sigmoidoscopy and fecal occult blood testing were performed simultaneously in 1,000 patients with no dietary restrictions. A total of 102 patients had a positive fecal occult blood test. Of these, 86 had visible blood in the rectum as demonstrated by sigmoidoscopy. Only two of the remaining 16 patients probably had a dietary-induced false-positive result on the occult blood test. Dietary restrictions for guaiac occult blood testing are unnecessary in more than 99 percent of patients.

Adolescent↗
PubMedDate not supplied

Relationship between the fecal occult blood test and benign anal disorders.

BACKGROUND/AIMS: The fecal occult blood test is a very useful method for mass screening for colorectal cancer. The possibility of the fecal occult blood test being positive is high even in benign anal disorders, but the relationship between anal disorders and the fecal occult blood test has not been fully studied. METHODOLOGY: During the period from November 1995 to April 1996, we performed both fecal occult blood test and sigmoid colonofiberscopy for 440 patients with anal disorders who visited our hospital for the first time. RESULTS: The positive fecal occult blood test rate was 18.8% (77/409) for those who had only anal disorders and no findings in the colon and rectum. The positive fecal occult blood test rate was significantly high in the cases with polyps (42.3%) and in those with colorectal cancer (60%). CONCLUSIONS: These findings suggested the need to analyze fecal occult blood test, keeping in mind that fecal occult blood test might be positive even without any malignant findings in the large intestine in about 20% of cases of patients have anal disorders when fecal occult blood test is performed.

Anus Diseases↗