PLASMA INTESTINAL ALKALINE-PHOSPHATASE ISOENZYMES IN NEONATES WITH BOWEL NECROSIS

Aim-To determine if the intestinal isoenzymes of alkaline phosphatase (ALP) are biochemical markers of bowel necrosis in neonates. Methods-P lasma ALP isoenzymes were measured in 22 babies with bowel necrosis, h istologically confirmed, and in 22 matched controls. The isoenzymes we re also measured in 16 infants with signs of necrotising enterocolitis , who recovered without histological confirmation of bowel necrosis. T he isoenzymes were separated by polyacrylamide gel electrophoresis. Au xiliary tests for identification included neuraminidase digestion and treatment with monoclonal and polyclonal antiplacental antibodies. Res ults-Intestinal ALP was detected in 16 infants with bowel necrosis-13 had fetal intestinal ALP (FI-ALP) and three had adult intestinal ALP ( AI-ALP). FI-ALP was detected in nine of the controls. In the babies wi th bowel necrosis intestinal ALP was found over all gestations, but in the controls only in those less than 34 weeks. The percentages of tot al ALP activity due to intestinal ALP were significantly higher in tho se with bowel necrosis compared with matched controls (p = 0.028). In babies of all gestations diagnostic sensitivity for the presence of in testinal ALP as a marker of bowel necrosis was 73% and diagnostic spec ificity 59%. In babies greater than 34 weeks' gestation, diagnostic se nsitivity fell to 60% but the test became completely specific. In two babies FI-ALP increased from zero/trace to high activity coincident wi th the episode of bowel necrosis. In 16 babies with signs of necrotisi ng enterocolitis but unconfirmed bowel necrosis FI-ALP was detected in four. Conclusion-Intestinal ALP seems to be released into the circula tion in some babies with bowel necrosis, but its detection does not ha ve the diagnostic sensitivity and specificity to be a reliable biochem ical marker of the condition.