1. In order to develop an improved differential
sugar absorption test for simultaneously assessing intestinal permeability and
lactose intolerance, methods were established for determining
raffinose,
lactose and
L-arabinose in human urine. Using
NAD(P)H-coupled enzymatic assays and fluorimetry, each
sugar was measurable over a concentration range of approximately 3-300 mumol/l in diluted urine specimens. 2. After an overnight fast, 40 normal volunteers drank an iso-osmotic
solution containing
raffinose,
lactose and
L-arabinose. The median 5 h urinary
sugar excretion was 0.26% of the ingested
raffinose, 0.05% of
lactose and 17.5% of
L-arabinose. 3. In 143 patients with
gastrointestinal disease, excretion of both ingested
raffinose and
lactose was significantly increased in coeliac disease in relapse or in partial remission and in
Crohn's disease, but not in the
irritable bowel syndrome, coeliac disease in remission or
ulcerative colitis. Excretion of
lactose, but not
raffinose, was increased in patients with mucosal
lactase deficiency, whereas excretion of
L-arabinose was reduced in all disease groups except
ulcerative colitis. 4. Discrimination between diseases was poor when based on individual
sugar recoveries, but improved dramatically when excretion was expressed relative to that of
L-arabinose. The
raffinose/
L-arabinose excretion ratio, an index of intestinal permeability, was greater than 0.08 in 15/15 untreated coeliac patients but less than 0.06 in all normal subjects and in 9/9
lactase-deficient patients, 15/16 recovered coeliac patients, 5/6 patients with
ulcerative colitis, 13/16 patients with
Crohn's disease and 61/62 patients with
irritable bowel syndrome.