Paper tests for occult blood in faeces and some observations on the fate of swallowed red cells.

Paper tests for occult blood were assessed on faecal specimens from adults. An orthotolidine/sodium perborate and a modified orthotolidine/peroxide test were found to be reasonably satisfactory. The Hematest and Occultest tablets and a paper guaiac test were unsatisfactory.A large number of false positive results was obtained in children and infants. It is suggested that this might be due to meat derivatives reaching the faeces more easily in the young. Red cells labelled with either Cr(51) or Fe(59) were swallowed by human volunteers. Although between 45% and 73% of the red cell iron reappeared in the faeces, the peroxidase activity of the labelled material dropped six-fold on passage through the alimentary canal.