THE d‐XYLOSE ABSORPTION TEST

Summary The metabolism of d ‐xylose in man is reviewed and the physiological and chemical basis of the d ‐xylose absorption test outlined. Study of 50 normal Australian subjects showed the normal result of the test to be 6·6 ± 1·4 grammes, and the lower limit of normal was taken as 3·8 grammes. The urinary volume was 414±164 ml., and the two‐hour blood level 37·0±7·2 mg. per 100 ml. These results agree with others in the literature. Two hundred xylose absorption tests were performed on 186 patients. It was found that impaired xylose absorption was almost always accompanied by other evidence of malabsorption, although steatorrhoea could be gross with normal xylose absorption. Xylose absorption was usually depressed in sprue, adult coeliac disease, severe infective enteritis and other primary small bowel diseases, as well as in elderly patients with extensive vascular disease. The test gave variable results after gastrectomy and in liver disease, the reticuloses and rheumatoid arthritis. The result was usually normal in pernicious anaemia, pancreatic disease and diabetes mellitus. Impaired xylose absorption was significantly related to hypo‐albuminæmia, but not to folic acid, vitamin B 12 or fat absorption, or to serum calcium or potassium levels.