Cows' milk induced intestinal bleeding in infancy.

Current United Kingdom Department ofHealth recommendations on infant feeding state that 'milks considered suitable for inclusion in the diet of infants from the sixth month are human milk, infant formulas, follow-up milks and whole pasteurised cow milk'.' Recently, however, controversy has arisen as it has been suggested that ordinary cows' milk should not be given before 1 year of age because of its relatively low iron and vitamin content,2 and because it is said to be associated with subclinical but appreciable gastrointestinal bleeding in infancy.3 This review aims to examine published work relating to the association between feeding cows' milk to infants and small children and the subsequent development in them of blood loss from the gastrointestinal tract. It has been established that normal infants lose small amounts of blood in their stools; it has been estimated that the average 'physiological' loss of blood is 0-64 ml/day (range 0-17-2-5 ml/day).4 Although the presence of gross blood in the stool (haematochezia) is obvious, detection of occult gastrointestinal blood loss is more difficult. Interpretation of the available published reports is complicated by the application of tests of differing sensitivity and specificity. One of the most sensitive methods for the identification of occult enteric blood loss detects chromium-51 (5'Cr) labelled erythrocytes in incinerated faeces.±7 Other workers have used the orthotolidine reaction to detect faecal occult blood.8 9 Most workers, however, have used the guaiac test; orthotolidine gives a positive result with blood in a 1:20 000 dilution with saline, whereas guaiac gives a positive result in a 1:100 to 1:5000 dilution. Guaiac is a colourless leucodye that becomes coloured in the presence of hydrogen peroxide and haemoglobin. Unfortunately, this test reacts with many non-haemoglobin substances and poor sensitivity and specificity may confound interpretation; the commerical guaiac Hemoccult test3 10 is known to underestimate blood loss in stools." On the other hand, the highly sensitive tests may not be specific and carry a high false positive rate. Specific and quantitative tests for the determination of faecal haemoglobin (for example, the HemoQuant test) have been developed'2 and used to measure blood loss from the gastrointestinal tract of infants.3 HemoQuant is a quantitative, exquisitely sensitive test specific for faecal haem which utilises purification methods that remove non-haemoglobin porphyrin derivatives (for example, chlorophyll). The assay is based on the chemical conversion of non-fluorescing haem to intensely fluorescent porphyrins. Proof that a positive result represents haem derived porphyrin is based on its solubility, characteristic spectral and chromatographic properties, and on the finding that it increases proportionately with ingested blood. 2 Alquist et al, in a comparative study, found the HemoQuant test to be considerably more sensitive and specific in the detection of faecal occult blood than the Hemoccult test. '3 HemeSelect (SmithKline Diagnostics), the latest addition to the European market, is a sensitive and specific immunological test for faecal occult blood based on reverse passive haemagglutination which has yet to be applied to the study of occult blood loss in children.