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

Fecal occult blood manifestation of intestinal Eimeria spp. infection in rabbit

The relationship between oocysts production and fecal occult blood manifestation was studied in rabbits experimentally infected with a single species of Eimeria. Pure single Eimeria species infection in non-infected rabbits for 6 species of Eimeria, namely: Eimeria media, Eimeria magna, Eimeria perforans, Eimeria coecicola, Eimeria piriformis, and Eimeria exigua were produced using a single oocyst. Fecal samples from these single Eimeria species infected rabbits were collected daily from day 1 through day 23 post-infection (DPI) to observe for oocysts shedding and also to test for presence of fecal occult blood (FOB). Rabbits infected with E. perforans were positive for FOB test (FOBT) reaction when their OPG exceeded 2.2x105 at 11 and 12 DPI. FOBT positive reactions were also seen in naturally infected rabbits with concurrent infections, of E. perforans and E. media as well as of E. perforans and E. magna. Thus, E. perforans was observed to cause intestinal hemorrhage during the period of massive oocyst shedding. This phenomenon was not seen in the other Eimeria species that we had examined. This is also the first report on the association of E. perforans infection with intestinal hemorrhage in rabbit.

Development of a faecal occult blood test to determine the severity of Haemonchus contortus infections in sheep

Haemonchus contortus commences feeding on host blood by day 11 of infection, which leads to the presence of blood in the host's faeces. This study examined the capacity for a faecal occult blood (FOB) test to determine the severity of H. contortus infection in sheep at pasture, and to predict a rise in worm egg count (WEC) as infection matures. Diluted faeces were assayed with Bayer Hemastix and the change in colour of the reagent patch was scored on a 9-point scale from 1 (negative) to 5 in half unit increments. Performance of the test was compared with four benchmarks for severe infection: (1) WEC>2000 on test day; (2) WEC>2000 on test day or 3 days later; (3) WEC>2000 on test day or 3 or 7 days later; and (4) WEC>2000 on test day or 3, 7 or 10 days later. For a FOB score > or = 3, the frequency of false positive results was high (31.6%) for benchmark 1 but decreased to 3.6% as the definition of severe infection was extended to include WEC>2000 on the test day or 3 or 7 days later. Sensitivity (92.0%), specificity (94.2%) and predictive value of a negative test result (87.5%) were also high for benchmark 3. By detection of blood in faeces during heavy H. contortus infections prior to the emergence of high WECs, the test provided an early indication of imminent haemonchosis. Positive FOB test results are also likely to arise from other causes of blood in faeces such as fascioliasis, coccidiosis and some bacterial enteritides. Further field studies are needed to validate the method as a diagnostic test for determining the severity of H. contortus infections under diverse environmental and sheep husbandry conditions.

Diagnosis of occult blood in human feces using matrix-assisted laser desorption ionization/time-of-flight mass spectrometry

BACKGROUND

Guaiac-based chemical tests may be the most cost-effective for routine screening of fecal occult blood (FOB). Unfortunately, such approaches still suffer from the unreliability of the incidence of false-positive and false-negative results in subjects who are on an unrestricted diet. We developed a rapid, automatic, and reliable detection method for FOB using matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF MS).

METHODS

The water-soluble alpha- and beta-chain hemoglobins (Hb), which are the most predominant proteins found in blood, were used as protein biomarkers for the diagnosis of FOB. The saturated 4-hydroxy-alpha-cyanocinnamic acid (alpha-CHC) solution was found to be the best MALDI matrix for Hb analysis.

RESULTS

The MALDI-TOF MS results were consistent with those provided through conventional chemical analysis, however, the sensitivity for the detection of FOB when using MALDI-TOF MS is approximately 10-100 times higher. In addition, the materials that commonly interfere with the conventional chemical assaying of FOB do not interfere with the detection of the Hb biomarkers during MALDI-TOF MS analysis.

CONCLUSIONS

We demonstrate that MALDI-TOF MS analysis of Hb biomarkers is an alternative approach toward the rapid diagnosis of FOB.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the detection of hemoglobins as the protein biomarkers for fecal occult blood

In this study, we discover that hemoglobins (Hb), highly water-soluble globular proteins that are the most predominant proteins detected by matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry in blood, can be used as protein biomarkers for fecal occult blood (FOB). Hemoglobins were extracted from the feces with pure water and separated from the solids in feces through centrifugation. Singly charged molecular ions of Hb-related alpha chains (theoretical MW: 15 126) and beta chains (theoretical MW: 15 867) were detected by MALDI-TOF operated in linear mode using 4-hydroxy-alpha-cyanocinnamic acid (alpha-CHC) as the matrix (with a volumetric ratio of 1:1). The detection limit of FOB using this method is estimated to be lower than 0.1 microg blood per mg of feces, which is approximately 10 to 100 times lower than that of the conventional chemical approaches. The foods and dietary supplements that commonly interfere with the conventional chemical assays of FOB - such as animal blood food products and tablets containing iron and vitamin C - do not interfere with the detection of Hb biomarkers during MALDI-TOF analysis.

Molecular stool screening for colorectal cancer

BACKGROUND

Mass screening for colorectal cancer reduces mortality and, with recent advances in molecular genetics, molecular stool-based tests have produced promising results. This article reviews this innovation and discusses its clinical significance.

METHODS

Medline searches were used to identify recent key articles relating to stool-based testing. Further articles were obtained by manual scanning of the reference lists of identified papers.

RESULTS

Current screening methods are based on endoscopic, radiological and stool-based testing. Recent recognition of the adenoma-carcinoma sequence and pathophysiological studies of colonic epithelium have enabled tumour markers to be used in the screening setting. Non-invasive molecular stool testing has now been shown to have a high sensitivity and specificity.

CONCLUSION

Recent studies on molecular stool-based testing have shown higher sensitivity and specificity than earlier studies, but larger clinical trials are required. Laboratory methods are still undergoing research, with the aim of improving sensitivity to allow large-scale testing.

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