JAMES KING-HOLMES / SCIENCE PHOTO LIBRARY JAMES KING-HOLMES / SCIENCE PHOTO LIBRARY
Hydrogen peroxide solution is applied to faecal samples on a guaiac-impregnated filter paper in a test kit submitted in a national screening programme. A resulting transient blue colour would indicate the possible presence of occult (hidden) blood with a need for further investigations for possible bowel cancer or polyps.
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