Radionuclide determination of gastrointestinal blood loss

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.

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.

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.