[The occult blood reaction].

The faecal benzidine assay has been replaced during the last few years by a great number of different assays on occult blood in faeces. The causes of occult blood at children are different from adults. Which test should be used depends on the desired sensitivity of 2 à 3 mg haemoglobin/g faeces are most suitable to prevent false-positive and false-negative results. To reduce false-negative results it is recommended to perform the assay on three successive days.