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Single and/or combined food intolerance/malabsorption may cause nonspecific, functional gastrointestinal (GI) complaints. In lactose-intolerant patients we evaluated the influence of additional food intolerance/malabsorption with hydrogen (H 2 ) breath tests. In a retrospective analysis of charts from 279 lactose-intolerant patients, we found 128 patients with only lactose intolerance (LIT). Then, we identified 106 LIT patients with additional histamine intolerance (HIT). Additionally, 45 LIT and HIT patients also had fructose malabsorption (FM). A hydrogen (H 2 ) breath test was performed to evaluate LIT and FM. A serum diamine oxidase value of <10 U/mL and a response to a histamine-reduced diet was used to identify HIT. Using pairwise comparison with the Kruskal-Wallis test to associate the area under the curve (AUC) of LIT patients and, LIT with HIT, to LIT with HIT and FM it was found, that the exhaled hydrogen values were significantly higher in patients with two-fold and triple combined food intolerance/malabsorption ( p < 0.004 and p < 0.001, respectively). Within the pool of 170 LIT patients with >20 ppm increase of expiratory H 2 from baseline, there were 74 LIT-only patients, 60 LIT with HIT patients, and 36 LIT patients with additional HIT and FM. With the Kruskal-Wallis test AUCs demonstrated a significant difference between all three groups ( p = 0.024). In patients with LIT, the presence of additional food intolerance/malabsorption, significantly increases expiratory H 2 values. We demonstrate evidence, which may suggest HIT to embody an own GI disorder as food intolerance/malabsorption.

Carbohydrate malabsorption and subsequent gastrointestinal symptoms are a common clinical problem in pediatrics. Hydrogen (H 2 ) and methane (CH 4 ) breath tests are a cheap and non-invasive procedure for diagnosing fructose and lactose malabsorption (FM/LM) but test accuracy and reliability as well as the impact of non-hydrogen producers (NHP) is unclear. CH 4 breath tests (MBT), blood sugar tests (BST) and clinical symptoms were compared with H 2 breath tests (HBT) for FM/LM. 187/82 tests were performed in children (2 to 18 years) with unclear chronic/recurrent abdominal pain and suspected FM/LM. In FM and LM, we found a significant correlation between HBT and MBT/BST. In LM, MBT differentiated most of the patients correctly and BST might be used as an exclusion test. However, additional MBT and BST had no diagnostic advantage in FM. NHP still remain a group of patients, which cannot be identified using the recommended CH 4 cut-off values in FM or LM. Reported symptoms during breath tests are not a reliable method to diagnose FM/LM. Overall a combined test approach might help in diagnosing children with suspected carbohydrate malabsorption.

The measurement of hydrogen in exhaled air and changes in the concentration of blood glucose and urine galactose excretion are indirect methods of diagnosing hypolactasia. The aim of this study was to compare a portable breath hydrogen analyser (Micro H2) with a widely used model (Quintron MicroLyzer) and to compare them with the blood glucose, urine galactose, and gastrointestinal symptoms in the lactose tolerance test. After an overnight fast, 44 volunteers (18-66 y) ingested 50 g lactose in a single oral dose. Changes in exhaled breath hydrogen concentrations were measured with the two analysers, and changes in blood glucose and urinary galactose were assayed for 4 h and used as a reference. Eighteen subjects were diagnosed as maldigesters according to our gold standard of at least two positive tests out of the three: breath hydrogen by Quintron, blood glucose concentration, and urine galactose excretion. The highest increase in the breath hydrogen concentration over the baseline was highly variable: 44-366 ppm (Micro H2) or 27-187 ppm (Quintron MicroLyzer). The sensitivity, specificity, and positive and negative predictive values of the Micro H2 compared to the gold standard were 83%, 96%, 94% and 89%, respectively. Overall agreement was 91% (95% CI 78-97%). Compared to the Quintron, the diagnoses were identical in 100% of the cases (92-100%). Thus, for diagnosing hypolactasia, the Micro H2 appeared as reliable for measuring breath hydrogen concentrations as Quintron MicroLyzer commonly used in oral lactose tolerance tests.

Breath hydrogen (H2), collected by end-expiratory sampling, was measured in twenty-five patients with abdominal symptoms or diarrhoea after ingesting 50 g. of lactose. This was compared with established tests of hypolactasia. Fifteen patients with a blood-glucose rise of more than 20 mg. per 100 ml. had less than 4 parts per million (p.p.m.) rise in breath H2 at 2 hours. In contrast, ten patients with blood-glucose rises of less than 20 mg. per 100 ml. had more than a 20 p.p.m. H2 rise (mean 85.8 p.p.m. plus or minus s.d. 44.3) at 2 hours. Similarly, two patients with normal jejunal lactase activity had no significant H2 production, whereas six patients with hypolactasia had more than a 20 p.p.m. rise in H2. Symptoms related to milk or lactose ingestion were found to be unreliable. End-expiratory sampling of breath H2 would seem to be a simple, non-invasive, and accurate method of diagnosing hypolactasia, which is also very acceptable to patients. This should make it a valuable tool both in diagnostic gastroenterology and in epidemiological surveys.