Reliability of chemical tests for fecal occult blood in hospitalized patients

Comparison of a guaiac and an immunochemical faecal occult blood test for the detection of colonic lesions according to lesion type and location

We investigated variations in sensitivity of an immunochemical (I-FOBT) and a guaiac (G-FOBT) faecal occult blood test according to type and location of lesions in an average-risk 50- to 74-year-old population. Screening for colorectal cancer by both non-rehydrated Haemoccult II G-FOBT and Magstream I-FOBT was proposed to a sample of 20 322 subjects. Of the 1615 subjects with at least one positive test, colonoscopy results were available for 1277. A total of 43 invasive cancers and 270 high-risk adenomas were detected. The gain in sensitivity associated with the I-FOBT was calculated using the ratio of sensitivities (RSN) according to type and location of lesions, and amount of bleeding. The gain in sensitivity by using I-FOBT increased from invasive cancers (RSN=1.48 (1.16–4.59)) to high-risk adenomas (RSN=3.32 (2.70–4.07)), and was inversely related to the amount of bleeding. Among cancers, the gain in sensitivity was confined to rectal cancer (RSN=2.09 (1.36–3.20)) and concerned good prognosis cancers, because they involve less bleeding. Among high-risk adenomas, the gain in sensitivity was similar whatever the location. This study suggests that the gain in sensitivity by using an I-FOBT instead of a G-FOBT greatly depends on the location of lesions and the amount of bleeding. Concerning cancer, the gain seems to be confined to rectal cancer.

Evaluation of the sensitivity and specificity of four laboratory tests for detection of occult blood in cockatiel (Nymphicus hollandicus) excrement

OBJECTIVE

To compare sensitivity and specificity of cytologic examination and 3 chromogen tests for detection of occult blood in cockatiel (Nymphicus hollandicus) excrement.

ANIMALS

20 adult cockatiels.

PROCEDURES

Pooled blood from birds was divided into whole blood and lysate aliquots. Excrement was mixed with each aliquot in vitro to yield 6 hemoglobin (Hb) concentrations (range, 0.375 to 12.0 mg of Hb/g of excrement). For the in vivo portion of the study, birds were serially gavaged with each aliquot separately at 5 doses of Hb (range, 2.5 to 40 mg/kg). Three chromogen tests and cytologic examination were used to test excrement samples for occult blood. Sensitivity, specificity, and observer agreement were calculated.

RESULTS

In vitro specificity ranged from 85%to 100% for the 3 chromogen tests and was 100% for cytologic examination. Sensitivity was 0% to 35% for cytologic examination and 100% for the 3 chromogen tests on samples containing >or= 1.5 mg of Hb/g of excrement. In vivo specificity was 100%, 90%, 65%, and 45% for cytologic examination and the 3 chromogen tests, respectively. Sensitivity was 0% to 5% for cytologic examination and >or= 75% for all 3 chromogen tests after birds received doses of Hb >or= 20 mg/kg. Observer agreement was lowest for cytologic examination.

CONCLUSIONS AND CLINICAL RELEVANCE

Chromogen tests were more useful than cytologic examination for detection of occult blood in cockatiel excrement. The best combination of sensitivity, specificity, and observer agreement was obtained by use of a chromogen test.

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.

Is upper gastrointestinal endoscopy indicated in asymptomatic patients with a positive fecal occult blood test and negative colonoscopy?

PURPOSE

There are no recommendations as to whether endoscopic evaluation of the upper gastrointestinal tract is indicated in asymptomatic patients who have a positive fecal occult blood test and a negative colonoscopy.

SUBJECTS AND METHODS

All asymptomatic patients with a positive fecal occult blood test who were referred for diagnostic endoscopy were identified. Patient charts, endoscopy records, and pathology reports were reviewed.

RESULTS

During the 5-year study period, 498 asymptomatic patients with a positive fecal occult blood test and negative colonoscopy were evaluated. An upper gastrointestinal source of occult bleeding was detected in 67 patients (13%), with peptic ulcer disease being the most common lesion identified (8%). Four patients were diagnosed with gastric cancer and 1 had esophageal carcinoma. In addition, 74 patients (15%) had lesions that were not considered a source of occult bleeding; these findings prompted a change in management in 56 patients (11%). Anemia was the only variable significantly associated with having a clinically important lesion identified (multivariate odds ratio = 5.0; 95% confidence interval 2.9 to 8.5; P <0.001).

CONCLUSIONS

Upper gastrointestinal endoscopy yields important findings in asymptomatic patients with a positive fecal occult blood test and negative colonoscopy. Our data suggest that endoscopic evaluation of the upper gastrointestinal tract should be considered, especially in patients with anemia.

Relative frequency of upper gastrointestinal and colonic lesions in patients with positive fecal occult-blood tests

BACKGROUND

Although bleeding lesions anywhere in the gastrointestinal tract can cause a positive reaction on guaiac-based fecal occult-blood tests, the relative frequency of upper gastrointestinal and colonic lesions is unknown.

METHODS

During a period of 30 months, we prospectively studied all patients with at least one stool specimen containing fecal occult blood who were referred for further evaluation. Fecal occult blood was detected by standard guaiac-based tests of stool specimens obtained as part of routine screening or of stool obtained by digital rectal examination. Patients with documented iron-deficiency anemia or active gastrointestinal bleeding were excluded from the study. All participants had a detailed history taken and underwent colonoscopy, followed by esophagogastroduodenoscopy.

RESULTS

Of the 409 patients with fecal occult blood who were referred, 310 were potentially eligible to participate, and 248 (mean age, 61 years; range, 40 to 89) were studied; 40 percent were women. We identified lesions consistent with occult bleeding in 119 patients (48 percent); in 71 bleeding lesions were found in the upper gastrointestinal tract, and in 54 they were identified in the colon. Six patients had abnormalities in both areas. The most common upper gastrointestinal lesions were esophagitis (23 patients), gastric ulcer (14), gastritis (12), and duodenal ulcer (10). Thirty patients with lesions in the upper gastrointestinal tract were long-term users of aspirin, ethanol, nonsteroidal antiinflammatory drugs, or a combination of these substances. The most common colonic lesions were adenomas more than 1.0 cm in diameter (29 patients), carcinoma (13), colitis (5), and vascular ectasia (5). Although the overall sensitivity of symptoms for the detection of gastrointestinal lesions was low, logistic-regression analysis demonstrated that the presence of symptoms in the upper gastrointestinal tract was associated with the detection of lesions in the upper gastrointestinal tract (odds ratio, 2.6; 95 percent confidence interval, 1.4 to 4.7). In both patients with symptoms and those without symptoms, the prevalence of lesions in the upper gastrointestinal tract was greater than or equal to that of colonic lesions.

CONCLUSIONS

In a group of patients with positive fecal occult-blood tests who were referred for further evaluation, from which those with iron-deficiency anemia and active bleeding had been excluded, upper gastrointestinal lesions were identified more frequently than colonic lesions.

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.

Significance of serum iron and ferritin in patients with colorectal adenomas

BACKGROUND

Colorectal adenomas are often detected on mass screening, although detection rates with fecal occult blood tests are low. The relationship between colorectal adenomas and the resulting blood loss was examined indirectly, using serum iron and ferritin levels.

METHODS

Serum iron and ferritin concentrations were measured in 184 men with colorectal adenomas (> or = 1 cm in 92; < 1 cm in 92) and in 92 healthy male controls. Values in the three groups were compared. In the patients with adenomas > or = 1 cm, serum iron and ferritin levels were compared on the basis of the site, number, histology, and degree of dysplasia of the adenoma.

RESULTS

The mean serum iron level was significantly lower in patients with adenomas > or = 1 cm than in controls (P < 0.05), although this level did not differ significantly between those with adenomas < 1 cm and controls. The mean serum ferritin level also was significantly lower in patients with adenomas > or = 1 cm than in those with adenomas < 1 cm and controls (P < 0.05, P < 0.01, respectively), although this level did not differ between those with adenomas < 1 cm and controls. There was no difference in mean serum iron or ferritin levels on the basis of the site, number, histology, or degree of dysplasia of the adenoma.

CONCLUSIONS

We conclude that decreased serum iron and ferritin levels are related only to adenoma size and that adenomas > or = 1 cm may bleed steadily, resulting in iron deficiency. However, low dietary intake of iron and fiber may be one of the causes of low serum iron and ferritin.

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.

Value of faecal alpha-1-antitrypsin, haemoglobin and a chemical occult blood test in the detection of gastrointestinal disease

Specimens from hospital out-patients and in-patients sent for faecal occult blood tests were also analysed for faecal alpha-1-antitrypsin and faecal haemoglobin. 453 stool specimens from 222 patients were analysed. The clinicians were only aware of the faecal occult blood test results, and diagnoses were made using conventional clinical and investigative criteria. Gastrointestinal bleeding or putative sites of bleeding were diagnosed in 98 patients, whereas in 81 patients putative sites of bleeding were not found or other cause of anaemia diagnosed. In 41 patients there was insufficient information to reach a definitive diagnosis. Comparison of the 3 faecal tests using these grouping methods showed that faecal alpha-1-antitrypsin performed best, with an accuracy of 89%, specificity of 90% and sensitivity of 88%, all significantly better (P < 0.001) than the faecal occult blood test (68%, 60% and 73%, respectively). There was no significant difference between the performance of the faecal occult blood and faecal haemoglobin tests. Faecal alpha-1-antitrypsin measurement may be a useful investigation in situations where a faecal occult blood test would normally be requested.

Detection of colorectal cancer by faecal alpha 1-antitrypsin

Alpha 1-antitrypsin was measured in 5-day faecal collections from patients with colorectal cancer or adenomatous polyps and a symptomatic control group. Collections were homogenized and lyophilized prior to measurement of alpha 1-antitrypsin by radial immuno-diffusion. Colorectal cancer dry weight concentrations were significantly higher than the symptomatic control results, with 57% having results greater than 95% normal values of this control group. There was no significant difference between adenomatous polyp dry weight concentrations and symptomatic control results. Wet weight concentrations were calculated from wet/dry ratios. Colorectal cancer wet weight concentrations were significantly higher than symptomatic control results with 48% having results greater than 95% normal values of this control group. Alpha 1-antitrypsin was also measured in non-lyophilized samples from an asymptomatic control group (n = 39). Colorectal cancer wet weight concentrations were significantly higher than asymptomatic control results, with 62% having results greater than 95% normal values of this control group. Faecal alpha 1-antitrypsin measurement deserves further assessment for use in detecting colorectal cancer.

Sensitized immunochemical method for the specific detection of human haemoglobin in dried biological samples

The authors describe a modified version of counterimmunoelectrophoresis of easy performance and high sensitivity. With this method human haemoglobin can easily and specifically be determined either in fresh or dried biological samples. Glutaraldehyde pretreatment of the samples results in the development of complexes with highly favourable electrophoretic mobility and precipitating capacity. By this chemical modification and use of a double set of samples with varying antigen-antibody proportion, the sensitivity of haemoglobin detection in erythrocyte-containing haemolysate and native blood was 300 ng/ml. The examination is easily performed, and without considerable outlay, even with conventional laboratory facilities. It is equally suitable for the detection of occult colorectal bleeding and for species-specific study of blood stains of unknown origin. The authors succeeded in identifying human haemoglobin even in a 42-month dried blood stain.

Faecal occult blood testing in symptomatic patients: comparison of three tests

This study examines three faecal occult blood tests, Haemoccult, Fecatwin and E-Z Detect, each with different sensitivities, to determine which is best suited for use in symptomatic patients--both for the detection of cancer and of non-malignant mucosal disease of the large bowel. A test was completed by 1025 patients before double-contrast barium enema and the performance of each test was determined from the result of this investigation. The study was completed by 969 patients. There were 49 patients with colorectal cancer, 92 patients with a cancer or a polyp greater than 5 mm, and 130 with some mucosal abnormality. The test most sensitive for blood, Fecatwin, detected 14 of 15 (93 per cent) cancers and 29 (69 per cent) of 42 patients with mucosal disease (including inflammatory bowel disease) but gave three times as many false positive results as the Haemoccult test, which is less sensitive for blood. The chance of a patient with a positive Haemoccult result having mucosal disease on barium enema was 24 of 47 patients (51 per cent) (two-thirds of these having colorectal cancer). A negative Haemoccult result, however, was unreliable and should not influence patient management. A test less sensitive for blood than Haemoccult was found to be of little value in symptomatic patients.

Substances that interfere with guaiac card tests: implications for gastric aspirate testing

Previous studies have shown that acidic pH and several ingestible substances can cause misleading guaiac tests of gastric aspirates. In this in vitro study, over 100 foods, beverages, and drugs were diluted to concentrations potentially present in the stomachs of outpatients being evaluated for gastrointestinal bleeding. These were mixed with known concentrations of blood and tested with different brands of guaiac cards. Decreased guaiac test sensitivity was associated with activated charcoal, dimethylaminoethanol, red chile, N-acetylcysteine, rifampin, red Jell-O (General Foods Corp, White Plains, NY), orange juice, Pepto-Bismol (Norwich Eaton Pharmaceuticals, Norwich, NY), simethicone, spaghetti sauce, and several red wines. Chlorophyll and methylene blue-containing tablets produced false-positive results, but other blue and blue-green colored tablets did not, except at high concentrations. Previously described false-negative results with vitamin C, bile, and certain antacids were confirmed, as were false-positive results with iodide, bromide, cupric sulfate, iron salts, and hypochlorite. Physicians should exercise caution when interpreting guaiac card tests of gastric aspirates, especially in the outpatient setting.

Effect of iron on the guaiac reaction

Most studies show that oral ingestion of iron does not cause a positive stool guaiac reaction. However, all in vitro studies show that iron does cause a positive guaiac reaction and some in vivo studies have shown a positive stool guaiac reaction in response to oral iron. This study examines this unresolved question. Twenty-five normal volunteers were given 900 mg of ferrous sulfate a day. Two Hemoccult II and two HemoQuant tests were obtained before and during iron therapy. All Hemoccult II tests were negative before and after oral iron. Four HemoQuant tests were slightly elevated before oral iron and one was slightly elevated after oral iron. Ferrous sulfate, 300 mg, was dissolved in 1 L of water. The solution was acidic (pH = 3.9) and produced a positive Hemoccult II test. When the solution was titrated with sodium hydroxide to a pH of greater than or equal to 6.0, iron precipitated out and the mixture no longer produced a positive Hemoccult II reaction. Our data show that ferric iron (Fe3+) in solution will give a positive guaiac reaction directly and ferrous iron (Fe2+) will give a positive guaiac reaction after hydrogen peroxide is added because it oxidizes Fe2+ to Fe3+. Iron solutions are acidic and when titrated toward a neutral pH, the iron is precipitated out and the solution is then guaiac-negative. Thus, our in vivo data confirm most previous in vivo studies; furthermore, the discrepancy between in vivo and in vitro studies can be explained as a pH-dependent phenomenon of in vitro iron solutions. Oral iron should not cause a positive guaiac reaction, and the HemoQuant results show no increase in occult blood loss in subjects on oral iron therapy.

Cost effectiveness of HemoQuant versus Hemoccult for colorectal cancer screening

Initial reports on HemoQuant, a new quantitative test for occult gastrointestinal bleeding, suggest it is more sensitive than Hemoccult. Increased detection of upper gastrointestinal tract bleeding and dietary hemoglobin may reduce HemoQuant's specificity in the screening setting. The authors performed a cost effectiveness analysis comparing Hemoccult and HemoQuant for colorectal cancer screening using assumptions based on probabilities and costs in the current literature, varying the specificity of HemoQuant. The analysis showed the marginal cost effectiveness of Hemoccult versus no test to be $43,000, and HemoQuant versus Hemoccult to be $296,000 if HemoQuant specificity is 0.95. The marginal cost effectiveness ratio increased to $601,000 if three HemoQuant tests were used. Survival benefit was small and highly dependent on Hemoccult sensitivity and mortality from colonoscopy if HemoQuant specificity was less than 0.9. The authors conclude that unless the high sensitivity reported for HemoQuant is accompanied by a specificity comparable to that of Hemoccult, HemoQuant may not be an acceptable alternative for colorectal cancer screening.

Effect of oral iron therapy on the upper gastrointestinal tract. A prospective evaluation

This study assesses the effect of oral iron therapy on the upper gastrointestinal tract and fecal occult blood testing. Fourteen healthy volunteers completed a checklist of gastrointestinal symptoms, underwent endoscopy and biopsy of the stomach and duodenum, and supplied a fresh stool sample for Hemoccult and HemoQuant testing. They then took ferrous sulfate 325 mg per os tid for two weeks and had the same evaluation repeated. Gastrointestinal symptoms were rated by the patients on a scale of 0-3, endoscopic findings were numerically scored (0-4), and the biopsies were graded blindly. Thirteen other healthy volunteers took ferrous sulfate 325 mg per os tid for one week and had Hemoccult testing of stool at days 0 and 7. All subjects developed dark stools, and significant nausea and diarrhea were noted (0.1 +/- 0.1 to 0.9 +/- 0.3, P less than 0.05 for both symptoms). Only 1/27 had a questionably trace-positive Hemoccult test (two observers disagreed) and no significant difference was seen in HemoQuant testing (1.4 +/- 0.5 to 1.8 +/- 0.7 mg Hb/g). A significant increase was seen in endoscopic abnormalities in the stomach (0.1 +/- 0.1 to 1.5 +/- 0.3, P = 0.003), consisting of erythema, small areas of subepithelial hemorrhage, and, in two subjects, erosions. Biopsies showed no significant change after iron therapy. We conclude that (1) oral ferrous sulfate rarely causes Hemoccult-positive stools, and patients with positive Hemoccult tests on iron therapy require further evaluation; and (2) oral iron may cause mild endoscopic abnormalities in the stomach which are of uncertain clinical significance.

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.

Gastrointestinal blood loss associated with running a marathon

Gastrointestinal bleeding has been observed in long-distance runners. We prospectively studied participants of the Eighth Annual Marine Corps Marathon to determine the incidence of gastrointestinal blood loss associated with long-distance running. Of 600 runners contacted, 125 (21%) returned a questionnaire as well as pre- and postmarathon stool specimens. Stool specimens converted from Hemoccult negative to positive in 29/125 (23%) of the participants, indicating that running the marathon was associated with gastrointestinal blood loss (P less than 0.001). The incidence of this conversion (negative to positive) was significant for both males (N = 68, P less than 0.001) and females (N = 57, P less than 0.05). Gastrointestinal bleeding appeared to be independent of age, race time, abdominal symptoms, and the recent ingestion of aspirin, vitamin C, or steak.

The current status of early detection and screening for colorectal cancer

There are several approaches to the early detection of colorectal cancer that currently are in use in various segments of the health care system. Herein, the status of cancer control research regarding symptom and risk factor assessment, sigmoidoscopy and colonoscopy, double contrast barium enema, and fecal occult blood testing is reviewed. In addition to the different technologies of early cancer detection, there are different models of disease control intervention. These include the routine clinical activities of primary care providers as well as programmatic screening of mass populations. The currently available techniques for early colorectal cancer detection appear better suited for existing patient care settings than for programs outside the direct supervision and follow-up of the health professional.

Acute stress ulceration

Stress ulceration is usually considered a mucosal abnormality of the oesophagus, stomach or duodenum in the critically ill. It is found to a varying degree in all such patients. Only about one-quarter of lesions are associated with blood loss and less than 5% need resuscitation and treatment. However, because treatment of established bleeding is unsatisfactory, and associated with a high mortality, prophylactic measures are usually employed. These include optimising gastric mucosal blood flow and oxygen delivery, correcting coagulation abnormalities and treating underlying infection. Enteral feeding should also be employed whenever possible. Other prophylactic measures currently used involve raising gastric pH above 4, with either antacids or H2 receptor antagonists. This is best achieved by measuring the gastric pH hourly and titrating it against an appropriate dose of either type of drug or a combination of both. Newer drugs, such as omeprazole, sucralfate and prostaglandins, are proving very successful in the treatment and prevention of gastric and duodenal ulcers and may prove even more effective than currently available agents.

Occult blood screening for colorectal carcinoma: a critical review

The author reviews the literature on occult blood surveillance for colorectal carcinoma. The guaiac-based Hemoccult (SmithKline Diagnostics, Sunnyvale, Calif.) test is the most reliable and widely used. However, testing is complicated by several technical issues that can affect clinical results, and even successful screening programs will miss a high proportion of tumors. Public compliance is often poor, and a number of indirect and "hidden" costs make surveillance programs much more expensive than is usually claimed. Almost all published screening trials are uncontrolled. They generally detect about 3-20 colorectal malignancies for every 10,000 people enrolled, but only about 5%-10% of occult blood reactions are due to cancer. Though screen-detected tumors tend to be at a relatively early stage, this does not imply any benefit of surveillance because of lead time and length biases inherent in the screening process. Only controlled trials can answer the central question of whether screening decreases mortality from bowel cancer. Two such trials are underway, but mortality data are not yet available from either.

Fecal alpha 1-antitrypsin and infant feeding

Stool samples from 232 infants aged 7 days to 18 months were analyzed for alpha 1-antitrypsin and for occult blood by two techniques. Among the 450 stool samples, no correlation between positive tests for occult blood and the concentration of alpha 1-antitrypsin was found. The alpha 1-antitrypsin concentration in the stool decreased after the age of 6 months in both breast-fed (P less than 0.05) and formula-fed (P less than 0.001) groups. In the 7- to 30-day-old infants, breast-feeding was associated with both lower fecal alpha 1-antitrypsin (P less than 0.001) and less frequent positive tests for occult blood (P less than 0.02) than found in the formula-fed infants. Between 6 and 12 months of age, alpha 1-antitrypsin was lower in cow milk-fed infants than in those receiving either breast-feeding supplemented with formula (P less than 0.01) or soy formula (P less than 0.05). Age and feeding differences in the concentration of alpha 1-antitrypsin in the stool may reflect subtle changes in gastrointestinal tract function in infancy.

Aspirin and gastrointestinal haemorrhage: a methodologic assessment

The literature on the association between Aspirin (ASA) use and gastrointestinal haemorrhage (GIH) has been reviewed. Thirteen control-studies were selected and examined for (i) the type of design (ii) the choice of outcome measures, and (iii) the adequacy of satisfying defined causation criteria and the influence of sampling strategies on one of these criteria--strength of association. Of the 13 studies seven were large scale randomized control trials (RCTs) and six were case-control studies. Among the outcome measures utilized in these studies and currently available for the assessment of GIH, we found none were uniquely satisfactory for use as a "gold standard". Furthermore, in none of these studies was the particular chosen outcome measure sufficiently satisfactory to allow firm conclusions on the issue of causation. None of the studies adequately met all the defined causation criteria or adequately eliminated the potential biases in the chosen sampling strategies. Thus the evidence that aspirin causes GIH fails to stand up to critical evaluation. This, of course, does not mean that ASA does not cause GIH. However, it is common practice for physicians to advise their patients with a prior history of GIH and or gastrointestinal symptoms to refrain from ASA use. This is probably sound advice in the setting where ASA is being used as a casual or short term analgesic or anti-inflammatory agent. But in the context of severe inflammatory joint disease when the use of ASA is clinically indicated, it should not be withheld on the basis of the risk of GIH. There is a widespread belief in medicine that by implication aspirin and other nonsteroidal anti inflammatory drugs are a common cause of bleeding from the gastrointestinal tract, yet it has been pointed out frequently [1-3] that the evidence to support the belief is weak and circumstantial. Despite this the perceived association of aspirin with gastrointestinal bleeding influences both pharmaceutical and clinical practice and often hinders or prevents the prescription of anti-inflammatory medication to patients with severe inflammatory joint disease. It was felt that a proper critical appraisal of the evidence was essential. It is unfortunate that the evidence most frequently cited implicating ASA as a cause of GIH is almost entirely related to the casual use of the drug. Thus our conclusions must be viewed with some caution in the patient group where this knowledge would be of most importance, that is in patients with inflammatory joint disease.

Five guaiac-based tests for occult blood in faeces compared in vitro and in vivo

Five guaiac-based faecal occult blood tests (Fecatest, Fecatwin Sensitive, Fecatwin, Haemoccult, Hemafecia) were compared in vitro and in vivo and the effect of time between sample application and development of the colour reaction was studied. In both type of experiments the sensitivity of Fecatest, Fecatwin Sensitive and Fecatwin was higher when the colour reaction was developed at 24-72 h than at 2 h after application of the sample but for Haemoccult and Hemafecia the sensitivity in in vivo experiments was constant or tended to decrease with time. In upper gastrointestinal bleeding false negative test results were obtained for Fecatest, Fecatwin Sensitive, Fecatwin, Haemoccult and Hemafecia in 21, 23, 38, 43 and 43%, respectively. In colorectal bleeding the corresponding percentages were 10, 10, 35, 35 and 35. Using the 51Cr-erythrocyte method, quantitative estimation of intestinal bleeding was performed in 20 patients with verified colorectal cancer and in 11 control patients. When the patient was bleeding from left hemicolon 29% of the Fecatwin, Haemoccult and Hemafecia test results were negative, 10% were negative for Fecatest and 14% for Fecatwin Sensitive. In patients with tumours in right hemicolon Fecatest and Fecatwin Sensitive were positive in all samples, whereas the other tests were negative in 10%. Experiments revealed that the proportion of false positives due to dietary factors correlated with the sensitivity of the tests.

Immunological detection of faecal occult blood in colorectal cancer

A new two-phase test kit for faecal occult blood combining a sensitive guaiac test (Fecatwin (S)ensitive) with an immunological test for human haemoglobin (FECA-EIA) was compared with three current guaiac tests (Fecatest, Fecatwin, Haemoccult) in 19 colorectal cancer patients and 11 controls on a restricted diet. A total of 43 48 h faecal samples (30 from cancer patients and 13 from controls) were collected for quantitative determination of faecal blood loss with the 51Cr method. Qualitative testing revealed that FECA-EIA was the most sensitive test, giving one (3%) false negative test result in the 30 tests on colorectal cancer patients and no false positives in the control subjects. It was also the only test that detected low-degree tumour bleeding. Fecatest and Fecatwin S were the most sensitive guaiac tests, giving 7 and 10% false negative test results, respectively, in the 30 colorectal cancer samples, whereas Haemoccult and Fecatwin gave 23% false negative test results. For screening purposes and in order to reduce costs it is suggested that only the positive test results of the very sensitive guaiac test (Fecatwin S) should be tested with the FECA-EIA test to eliminate false positive results. With this approach the diagnostic accuracy of the new two-phase test will be about twice as good as for the Haemoccult test.

Self-reported dark red bleeding as a marker comparable with occult blood testing in screening for large bowel neoplasms

The study was designed to determine the prevalence of large bowel symptoms in an adult working population and to assess their value in screening for large bowel neoplasms. A symptom questionnaire was sent to workers in two large organizations and the results were compared with faecal occult blood testing in the same individuals using Haemoccult (Eaton Laboratories). Completed symptom questionnaires and Haemoccult test kits were returned by 916 out of a total of 1805 employees over the age of 40 (compliance 50.7 per cent). Twenty-eight (3.1 per cent) were Haemoccult positive and 114 (12.4 per cent) had one or more symptoms. All positives (129 persons) were examined by flexible sigmoidoscopy and barium enema. No cancer was found but 7 patients with adenomas greater than 10 mm diameter were discovered. Each of the 7 patients reported at least one symptom (dark red bleeding in 4, bright red bleeding in 2 and diarrhoea in 1) and 6 were Haemoccult positive. There was no individual with a Haemoccult positive adenoma without symptoms. Predictive values for adenomas over 10 mm for Haemoccult positive tests (21 per cent), self-reported dark bleeding (16 per cent) and diarrhoea (17 per cent), were significantly higher than for other symptoms. The predictive value rose significantly to 46 per cent for Haemoccult-positive patients who in addition had at least one symptom (P less than 0.05) and to 57 per cent for Haemoccult positive with dark bleeding. These combinations of Haemoccult- and symptom-positive results increased the specificity of 97.6 per cent for Haemoccult alone to values over 99 per cent without reducing sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Haematological aspects of life with an ileostomy

The haematological aspects of life with an ileostomy have been studies in 51 patients, of whom 39 had had ulcerative colitis and 12 had Crohn's disease. The findings in these patients have been compared with those in 39 healthy volunteers who were matched for age and sex with the 39 patient who had had ulcerative colitis. There was evidence of a mild degree of iron deficiency in the patients with an ileostomy. This was partly due to a pre-existing iron deficiency resulting from their preceding illness and operation, as the abnormality was less pronounced in the patients in whom the ileostomy had been established for more than 3 years. There was some evidence of excessive iron loss and a controlled trial of ferrous fumurate showed that the iron deficiency was largely corrected by this means. Circulating levels of vitamin B12 were normal, but it is relevant that some of the Crohn's disease group were receiving parenteral supplements. The absorption of vitamin B12 wa low in the patients with Crohn's disease who had had an ileal resection of more than 17 cm. The absorption of vitamin B12 in the patients who had had ulcerative colitis was increased and possible mechanisms are discussed. All but one of the patients had normal levels of plasma folate and in all the red cell blood folate was normal, which can be taken as an indication of a good dietary intake and adequate absorption.

Colorectal cancer: knowledge and attitudes of doctors in Victoria

Successful introduction of screening for early colorectal cancer will depend, at least in part, on doctors' knowledge and attitudes. A 34-item questionnaire was sent to a random sample of one in five doctors in Victoria, with a final completion rate of 65%. The survey revealed gaps of knowledge, particularly about recognition of high-risk groups. Only 12% were aware of the degree of increased risk faced by first-degree relatives of patients with colorectal cancer and only 10% recognised the similar increase in risk for people with a history of resected colorectal cancer. While 73% of doctors order faecal occult blood tests, only 9% were aware that the more reliable quaiac method was used for their patients. Overall, 38% considered that faecal occult blood testing was a practical method for screening for colorectal cancer. Most of the doctors who accepted occult blood screening would follow up a positive test with digital rectal examination (80%) and barium enema (75%), but only 58% would want sigmoidoscopy performed and 34% colonoscopy. The diagnostic potential of digital rectal examination and sigmoidoscopy was over-estimated by half of the doctors surveyed. Recognition of subjects at high risk for colorectal cancer, and knowledge about the proper use, follow-up, and potential for screening of faecal occult blood tests need emphasis in medical educational programmes.

The incidence of occult bleeding per rectum in a general practice in Scotland: a study using haemoccult

Haemoccult (Eaton Laboratories) was offered to all 405 subjects aged 45 to 65 years in a Scottish, rural general practice as a screening test for occult bleeding per rectum. Subjects contacted verbally had a compliance rate of 85.2 per cent and those by post 59.5 per cent--2.6 per cent (7) returned positive tests. Of these seven, one refused follow-up. Two had diverticular disease, one had haemorrhoids, one had a possible polyp, one had ingested aspirin and also had a few diverticula. In one patient, no cause of bleeding was found. The last two and one with diverticular disease were negative on re-testing. In general, the test was aesthetically acceptable to undertake for both patient and doctor and provided a suitable screening technique for occult bleeding.

Colorectal cancer screening

The efficacy of Hemoccult screening for colorectal carcinoma is analyzed utilizing five criteria which a screening test should fulfil before it is used for mass screening. The Hemoccult screening protocol has serious weaknesses. It is at best 83% sensitive for cancer and much less sensitive for polyps. An asymptomatic person with one or more positive Hemoccult slides only has a 12% chance of having cancer. In addition, patient acceptance of mass Hemoccult screening is questionable. There is currently little information on potential survival benefits, and Hemoccult screening is expensive with one quarter of all costs incurred in the diagnostic evaluation of false positives. There is insufficient evidence to recommend Hemoccult colorectal cancer screening in asymptomatic persons as a cost-effective practice.

Comparison of five guaiac resin paper tests for demonstrating the presence of blood in faeces

Four recently available kits of guaiac resin-impregnated paper for demonstrating the presence of blood in faeces were compared with Hemoccult II in in vitro testing. Hemo-FEC most closely resembled Hemoccult II in its sensitivity with freshly prepared kits and kits prepared one week earlier with or without rehydration before testing. Gamma Fe-Cult and Fecatest were more sensitive than Hemoccult II whereas Camco-Pac Guaiac was much less sensitive. Rehydration of kits prepared several days beforehand appears to be useful in restoring sensitivity lost by all the kits tested.

Cow milk feeding in infancy: gastrointestinal blood loss and iron nutritional status

Eighty-one normal infants were studied between 112 and 196 days of age. Thirty-nine infants were fed pasteurized cow milk and the remainder were fed either Enfamil or heat-treated cow milk. During the age interval of 112 to 140 days, the proportion of infants with guaiac-positive stools was significantly (P less than 0.01) greater among infants fed pasteurized cow milk than among those fed Enfamil or heat-treated cow milk. Similarly, infants fed cow milk had a significantly (P less than 0.001) greater number of guaiac-positive stools than did the other infants. After 140 days of age, there was no difference between feeding groups in the number of guaiac-positive stools. No significant differences were observed in mean hemoglobin, hematocrit, serum iron, total iron-binding capacity, or transferrin saturation between feeding groups nor between infants with and those without guaiac-positive stools, It is concluded that pasteurized cow milk should not be fed before 140 days of age.

Colorectal cancer--Prevention and detection

The American Cancer Society estimates that during 1980, there will be approximately 114,000 new cases of colorectal cancer in the United States--second only to lung cancer (an expected 117,000 cases) in incidence for internal malignant neoplasms. There will be 53,000 deaths this year from colorectal cancer. The low five-year survival rate of 42% in related primarily to late diagnosis. Therefore effective methods of making an earlier diagnosis are important. The use of fecal occult blood testing and sigmoidoscopic examination (rigid or flexible) appear to be tools that will make earlier diagnoses of colorectal cancer. Colonoscopy and barium enema are indicated if symptoms of colorectal cancer are present or if indicated from findings noted on fecal occult blood testing or sigmoidscopy. Determinations of carcinoembryonic antigen levels are of no practical value in colorectal cancer screening. In asymptomatic patients, fecal occult blood testing is recommended annually beginning at age 50, while sigmoidoscopy should be performed at age 50, repeat in one year, then performed every three years. The two chief areas of interest in colorectal cancer prevention are the removal of neoplastic polyps at the time of endoscopy, and the role of nutrition to decrease fat and increase fiber in the diet.

An immunofluorescent test for faecal occult blood

An immunological test for faecal occult blood is described, which is suitable for screening purposes. Fluorescein-labelled rabbit anti-human-haemoglobin serum is mixed with an aqueous faecal suspension, and free antibody is bound to a membrane sampler coated with human haemoglobin. The fluorescence on the membrane sampler is measured in a fluorometer, and the level of haemoglobin in the suspension is estimated. Advantages over chemical tests include absence of cross-reaction with animal haemoglobins, minimal observer error, and an adjustable sensitivity.

Occult faecal blood loss determined by chemical tests and a 51 Cr method

Stools from volunteers participating in an acetylsalicylic acid (ASA) study were examined during periods with restrictive and liberal diets. With 51Cr-determined faecal blood less than 2 ml/100 g, the rates of positive benzidine and 3,3' ,5,5'-tetramethylbenzidine (TMB) tests were about 5% and 25% for periods with restrictive and liberal diets, respectively. Similarly, Fecatest showed 2% positive tests on a restrictive and 8% on a liberal diet, whereas Hemoccult II slide and BM-test-Hemafecia showed less than 5% positive tests on both diets. When ASA-induced blood loss (mainly gastric) exceeded 5 ml/100 g faeces, the rate of positive benzidine and TMB tests, including the Hemo-Fec Test, varied from 87% to 100%. Fecatest detected half of these cases, whereas Hemoccult II and BM-test-Hemafecia were positive in less than one third. By repeated analyses of faecal specimens stored for 3 days, Fecatest showed a substantially increased sensitivity. We assume that benzidine and TMB tests are sensitive enough to detect occult blood loss from all levels of the gastrointestinal tract, but dietary restrictions are essential to reduce the rate of false-positive tests. Guaiac tests, perhaps with the exception of Fecatest, should be reserved for the detection of occult blood loss from the lower gastrointestinal tract.

A mass screening program for colorectal cancer using chemical testing for occult blood in the stool

Following five promotional and educational programs on CBS-TV news in Chicago, 54,101 Hemoccult kits were requested by the public and distributed by seven cancer detection facilities. Only 14,074 individuals completed the test. Six hundred and seventeen or 4.38% were positive. Two hundred and fifteen test positive persons failed to respond to repeated notification. In 123 positives, diagnostic tests by the private physician were considered incomplete. In 33 positives, the private physician did no further testing at all. In 152 positives, no abnormality could be found, but work-up was variable. One hundred and eighty-seven had abnormalities other than cancer, including 40 with polyps. Twenty-seven asymptomatic and two symptomatic cancers were found. Nearly two-thirds had Dukes A or B lesions, while one-third had Dukes C tumors. Public compliance in both completing kits and following through with positive results was low. Physician evaluation of positives was often incomplete. Chemical testing for occult fecal blood, when properly combined with other tests such as proctoscopy, has the potential for lowering mortality from colorectal cancer. Continued public and professional education is needed.

Progress report on controlled trial of fecal occult blood testing for the detection of colorectal neoplasia

Our controlled trial of screening for colorectal cancer has now been in progress for almost five years. Screening is accomplished by rigid sigmoidoscopy in control and study groups and, in addition, by fecal occult blood testing in the study group. Patients screened are men and women age 40 and older, mostly at average risk. Fecal occult blood testing is with Hemoccult slides with patients on a meat-free, high-bulk diet without hydration, and with a four-day storage interval between slide preparation and testing. Patients with positive slides undergo diagnostic investigation that includes both colonoscopy and double-contrast barium enema and, in some, an upper gastrointestinal series. Preliminary results to date include: patient baseline statistics and subgroup comparability, rate of positive slides of 1-4%, predictive value for neoplasia of 44-50%, false-positives of 0.5-2.1%, favorable Dukes' staging of cancers in the study group, and high patient compliance. Considerably more follow-up is need in our study and control population, and issues such as mortality and cost need to be addressed. Additional time will be necessary to provide firm conclusions.

Screening for colorectal cancer: an overview

The critical issue of whether to screen asymptomatic patients for colorectal cancer is related to expected benefits, the population at risk, sensitivity and specificity of available screening and diagnostic tests, cost-effectiveness, and patient compliance. Current screening programs in progress strongly suggest a survival benefit to those patients with a positive screening test but longer follow-up is necessary. Risk factors within the population have been defined, but further work is needed to identify more completely the high-risk subgroups for selective screening. Selective screening of high risk groups would be more productive than mass screening of standard risk patients. Screening and diagnostic tests in current use appear to be sensitive and specific, but more data will have to be examined. Screening with fecal occult testing has been shown to be feasible and productive, but cost-effectiveness must be demonstrated. Patient compliance has been high in well-motivated patients entering studies, but factors involved in health belief must be evaluated as a basis for patient orientation toward screening. Our goal for colorectal cancer is primary prevention--identification and elimination of environmental factors. Until then, secondary prevention may be a realistic achievement--the identification and eradication of precursor lesions and the diagnosis of early colon cancer.

False positive and negative hemoccult reactions on a normal diet and effect of diet restriction

The reliability of Hemoccult, a guaiac-impregnated slide for detecting faecal occult blood, was assessed on both normal and restricted diets. Two-hundred-and-twenty-five faecal samples were obtained from 40 patients on a normal diet, and 115 samples from 20 patients on a restricted diet. A single Hemoccult I test was performed on each sample. Faecal blood was quantitated by 51Cr red cell labelling. On a normal diet, the false positive rate was 11%. This reduced to 2% on a high fibre diet free of red meat and raw fruit and vegetables. This false positive rate is lower than has been previously reported for other, more widely-used, occult blood tests. The overall false negative rate was 48%; this diminished with increasing faecal blood loss.