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Luminol reaction for fecal occult blood -New application of a forensic blood detection method-

  Bleeding in the digestive system occurs when patients have ulcers, inflammation and cancers. Therefore, an early sign of such diseases may be microscopic blood in stool, which doctors refer to as “fecal occult blood” (FOB). The luminol reaction, which has been used in forensics to detect trace amounts of concealed blood, can also be applied for detection of FOB, according to Kindai University researchers, led by Ah-Mee Park, Ph.D, Associate Professor in the Department of Microbiology, Faculty of Medicine.

Key Points
1.Experiments have shown that the luminol reaction can be used to detect FOB in animals.
2.This is the first standard method to detect FOB in animal models for ulcers and cancers in the digestive system - which is simple, quick, economical and quantitative - making it applicable to use for any research laboratories.
3.It is hoped these findings will contribute to the furthering of research on gastric ulcers and colon cancer.

  FOB, or microscopic blood in the stool, is a sign of gastrointestinal diseases, such as intestinal ulcers and colon cancers. To discover the precise cause and new treatments for such diseases requires animal models, in which the levels of FOB are measured to assess the severity of gastrointestinal bleeding. Unlike in clinical human stool samples, however, there is no standard method to detect FOB in experimental animals.
Kindai University researchers present a simple method to detect FOB in mice, using the luminol reaction, which has been used to detect bloodstains at crime scenes, like those often seen in detective stories and TV shows. By mixing feces with a luminol solution, hemoglobin-containing fecal samples produce visible blue light (chemiluminescence). The levels of FOB are measured by the hemoglobin content; a higher content corresponding to a higher brightness level of the chemiluminescence - as measured by a luminometer. This method is simple, quick, economical, and quantitative, allowing researchers to detect FOB in experimental animals. The application of the luminol reaction in clinical medicine is expected to contribute to furthering disease research.

  Ah-Mee Park and Ikuo Tsunoda, “Forensic luminol reaction for detecting fecal occult blood in experimental mice” is published in the British scientific journal, BioTechniques, August 2018(Impact factor 2.030)

Details of the research
  Bloody stool samples were collected from mice with intestinal ulcers, which were induced by injection of indomethacin, a non-steroidal anti-inflammatory drug. Fecal samples were mixed with a luminol solution and observed in dark field. The blue chemiluminescence became detectable 4 hours after the injection, and the intensity of the chemiluminescence was measured by a luminometer. The levels of FOB were calculated by the ratios of the chemiluminescence intensities of fecal samples to the chemiluminescence intensity of a luminol solution alone.

  To detect FOB in human stool, there are two standard methods; the stool guaiac test and the hemoglobin antibody immunochemical test. The guaiac test using the colorimetric method is easy to operate, but lacks quantification and can be affected by other factors. On the contrary, the immunochemical test is expensive, but allows quantification of the hemoglobin content, is specifically for hemoglobin and is not affected by other factors. On the other hand, for experimental animal studies, researchers often assess the FOB levels by stool color and appearance since there is no standard method to detect and quantify FOB in animals.

Outlook for the future
  Since this FOB detection method is simple, quick, economical, and quantitative, most researchers in the field of gastrointestinal diseases can use it easily in their laboratories as a gold standard method, allowing for more precise assessment of their experimental results, as well as comparison of reports between different laboratories and scientific articles. The limitations of the luminol reaction applying to human stool samples include several factors that affect the reaction, for example, food or bleach. Nevertheless, this discovery will help advance the field of research in gastrointestinal diseases.

Profiles of Researchers
Name: Ah-Mee Park, Ph.D.
Affiliation: Dept. Microbiology, Kindai University Faculty of Medicine
Specialty: Microbiology, Free radicals
  Metropolitan DC Thoracic Society Annual Meeting: First Prize
  Annual Meeting of American Thoracic Society: Travel Award



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