Ultrasensitive latex-agglutination-test for the specific immunochemical detection and quantification of faecal occult blood loss

Investigation of small intestinal lesions in dialysis patients using capsule endoscopy

INTRODUCTION

Although gastrointestinal hemorrhage is an important complication for dialysis patients, the details of many points remain unclear with regard to small intestinal lesions.

METHODS

Capsule endoscopy was performed in fecal occult blood-positive dialysis (n =16) and non-dialysis (n = 20) patients after upper and lower gastrointestinal endoscopies failed to reveal hemorrhagic lesions.

FINDINGS

Erosive lesions were observed in 50.0% (8/16) and 25.0% (5/20) of the dialysis and non-dialysis groups, respectively. Vascular lesions were observed in 62.5% (10/16) and 25.0% (5/20), respectively. Vascular lesions were observed at a significantly higher rate in the dialysis patients (P = 0.041), but no significant difference was noted in erosive lesions (P = 0.188). Of patients taking proton pump inhibitor (PPI), Non-Steroidal Anti-Inflammatory Drugs, and antiplatelet drugs, only oral PPI administration was associated with vascular lesions (P = 0.02).

DISCUSSION

In dialysis patients, vascular lesions are the most common among small intestinal lesions, suggesting that they may have caused previously unexplained gastrointestinal hemorrhage in dialysis patients. It was also suggested that the frequent use of PPI may be a cause of small intestinal lesions.

Detection and diagnosis of blood in feces and urine: an overview

BACKGROUND

Detection of blood in feces or urine has long been regarded as an indicator of patient's state of health. The ease with which feces or urine may be obtained and patient's willingness to provide the specimen make detection of fecal occult blood or urine analysis one of the most commonly performed screening examinations. Historically, the inspection of feces or urine for diagnostic purpose has been practiced for centuries. Of late, management of renal or urinary tract abnormalities or investigation of anemia, gastrointestinal diseases and for early detection of colorectal cancer has assumed greater importance.

METHODS

The never-ending list of techniques for the diagnosis of disorders producing bleeding such as urine microscopy, urine cytology, urine based marker test, cytoscopy, ultra sonography, computed tomography, magnetic resonance imaging, to mention a few, and four categories of detection of fecal occult blood namely, radioanalytical, physical, immunochemical and chemical methods makes the study very interesting.

PURPOSE

This review attempts to overview various techniques, methods and methodologies for the diagnosis and detection of blood in feces and urine, in the direction of looking at past and current tests with an eye on future needs.

Early detection for colorectal cancer: new aspects in fecal occult blood screening

The authors report on promising diagnostic methods of occult intestinal bleeding and discusses the potential new strategy of early detection of colorectal carcinomas in respect to old and new diagnostic measures available. Because of the limited sensitivity and specificity of classical methods used for the demonstration of occult fecal blood, the authors recommend the introduction of new techniques and markers in screening practice. It is presumed that new discoveries in molecular biology will improve the accuracy of early colorectal cancer prevention. Their implementation into routine screening, however, will not take place in the near future. Until their realization, improved screening efficacy is expected from the use of more specific and sensitive blood tests.

Evaluation of new occult blood tests for detection of colorectal neoplasia

BACKGROUND

Hemoccult II, the guaiac-based fecal occult blood test used in most colorectal cancer screening programs, has an unsatisfactory sensitivity for asymptomatic colorectal neoplasms. We evaluated the relative performance of four fecal occult blood tests, directed against various components of the hemoglobin molecule.

METHODS

All tests, Hemoccult II, HemoccultSENSA (a more sensitive guaiac test), HemeSelect (an immunochemical test specific for human hemoglobin), and HemoQuant (the heme-porphyrin assay), were performed by 107 patients with symptomatic colorectal cancer and 81 patients with predominantly asymptomatic adenoma. Hemoccult-SENSA and HemeSelect were performed by 1,355 screenees.

RESULTS

HemeSelect and Hemoccult-SENSA had significantly higher sensitivity for colorectal cancer (97% and 94%, respectively) than the other tests. HemeSelect had the highest sensitivity for adenomas; in 45 patients with large (> or = 10 mm) adenomas, sensitivity was 76% for HemeSelect, 60% for HemoccultSENSA, and 42% for both Hemoccult and HemoQuant. In the screenees, estimated specificity was 97.8% for HemeSelect and 96.1% for Hemoccult-SENSA.

CONCLUSIONS

HemeSelect and Hemoccult-SENSA have the highest levels of sensitivity for detection of colorectal neoplasia, but the immunochemical test HemeSelect provides the best combination of specificity and sensitivity.

Double immunochemical screening test (hemoglobin and albumin) for the detection of occult intestinal bleeding

The authors have developed a combined electrophoretic-immunoprecipitation technique suitable for the simultaneous demonstration of two blood proteins, i.e., hemoglobin and albumin, in the feces. The analytical sensitivity of the method is 2 micrograms hemoglobin and albumin/ml. The technique is simple, inexpensive, and suitable for the reliable demonstration of occult intestinal bleeding for either inpatients or mass screening. This technique is an aid not only to the fact that bleeding can be detected, but to its intensity, as well. This new technique improves the diagnostic accuracy of early detection of carcinomas and polyps, presumably without raising significantly the number of "false-positive" reactions.

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.

[A new latex agglutination test for the immunologic detection of occult blood in stool]

An new latex agglutination system was developed for the detection of occult blood in the feces. Antibodies against human hemoglobin were raised in a goat. Blood in concentrations of 0.1 ml-8.0 ml/100 g feces were detected in vitro. The antibodies were separated and adsorbed to latex particles (0.3 microns). After in vitro standardisation of the new test system we compared the efficacy of the commonly used guaiac slide test for detection of occult blood in the stool (hemoccult-test) with the latex test system. A significant higher sensitivity could be reached with the latex test system. In a clinical study 61 patients were tested. In 31 of them occult blood was found with the latex test system while with the guaiac slide-test system no blood was detected using the same stool specimen. 13 of the 31 patients had a neoplastic lesion of the colon - 4 a colon carcinoma and 9 had adenomatous polyps of the large bowel larger than 5 mm in diameter. In the remaining patients the sources of intestinal bleeding were: upper gastro-intestinal bleeding sources in 8 patients and other colonic bleeding sources like diverticular disease, inflammatory bowel disease, hemorrhoids and a rectal ulcer in 8 patients. In 2 of the 61 patients the latex test was positive without endoscopic significance for the bleeding source.

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.

Screening of colorectal cancer

Colorectal cancer (CRC) remains a cancer in a disappointing location. However, its location clearly has an advantage that could theoretically permit efficient secondary prevention: the preceding of the cancer by a benign lesion, ie, the adenoma. Complete colonoscopy and its substitute, the double-contrast barium enema, and their specific limitations, must be reserved for high-risk patients: hereditary cancers and ulcerative colitis. For all the others, ie, adults of 45 years of age and with standard risks, the proposal is either to select the patients to be colonoscoped through occult blood testing of the stools or to perform a fiber sigmoidoscopy or a combination of both. Although imperfect, both methods allow the detection of polyps and cancers at a presymptomatic stage, when they are either benign or malignant, but localized and with a better prognosis. However, the absolute proof of the benefits of this strategy of screening would be the demonstration by controlled studies of a prolonged survival rate or a decrease in morbidity. Until now, this proof is not fully available.

A qualitative agar gel immunoprecipitin (IP) test for detection of fecal occult human hemoglobin

A versatile, qualitative, agarose gel immunoprecipitation (IP) test for the detection of fecal occult hemoglobin (Hb) was developed to provide a more accurate method for the detection of occult blood in stool. This test allowed detection of 0.2 mg human hemoglobin/g of stool after a 2-h incubation. In addition, a specimen application device which can accommodate a variety of specimens was developed for this test. A study of 252 clinical stool specimens revealed a close correlation in the results obtained at three separate laboratories. The IP test identified blood in 11 out of 24 specimens collected from patients with colorectal carcinoma as compared to 4 of 24 specimens positive with a guaiac-based Hemoccult II test. The simplicity of immunoprecipitation coupled with the high sensitivity and specificity of this technique suggests that this new test would be a very useful and effective means with which to screen for occult blood in stool.