Materials and Methods
All successive patients referred to our gastroenterology practice by general practitioners between January 2008 and May 2011 for evaluation of FGID were eligible for inclusion in this prospective study, except those with evidence of organic disease, which was assessed by routine haematology and biochemistry blood testing and also stool testing for calprotectin and pancreas elastase determined in two stool samples in all patients. Parasite and bacterial stool cultures were performed if clinically indicated. Upper and lower endoscopies with biopsies were required in patients older than 40 years or in patients with diarrhoea or faecal blood. Coeliac disease was excluded by antitranglutaminase antibodies or duodenal biopsies. One consultant gastroenterologist (CWS) performed all the medical and dietary history taking and physical examinations. The dietary history included two sections: an open question requesting a listing of avoided and poorly tolerated foods and then a specific list of the main fructose, fructooligosaccharide, galactosaccharide, lactose and sorbitol-containing foods as well as the 10 commonest food allergies in Europe. In addition, skin rashes, urticaria, rhinitis, headache, imperative defaecatory urge, changes in stool consistency related to mealtimes were documented. All patients completed a standardised questionnaire, which included the specific questions for classification of GI symptoms into FGID groups according to the Rome III criteria and additional questions regarding allergies, childhood and family history, central nervous, musculoskeletal and cardiac system symptoms, and the use of polyol-containing sweets and chewing gum. Patients were classified into FGID subgroups according to the Rome III criteria. The most prominent FGID was chosen for classifying each patient. The study was performed in accordance with the Helsinki Declaration of 1975 as revised in 1983.
Breath Test Protocol
Fructose and lactose breath tests were performed in all FGID patients by one laboratory technician (AM). No antibiotics, colonoscopy or laxatives were permitted within 14 days and a specific low-saccharide diet was adhered to 1 day before the tests. Patients arrived for testing in the morning after fasting overnight and without having smoked, chewed gum or performed vigorous exercise for at least 4 h. Chlorhexidine mouthwash was used and teeth were brushed before testing. The breath tests were performed in randomised, patient-blinded sequence on two separate occasions at least 4 days apart. Breath samples were collected in sealed glass tubes (Quintron Instruments, Milwaukee, WI, USA) before and hourly for 5 h after ingestion of lactose 50 g or fructose 35 g dissolved in 300 mL water. Hydrogen, methane and CO2 concentrations were measured within 72 h using the Quintron BreathTracker SC® (Quintron Instruments). Hourly testing was chosen based on our laboratory pilot data, where identical qualitative results were obtained as with sampling every 15 min and concentrations were stable in the tubes for 3 weeks. Malabsorption was defined as an increase of >20 ppm in hydrogen or >10 ppm in methane levels over baseline twice in succession. The numbers of patients with early rises (in the first 60 min) above the 20 ppm threshold in breath hydrogen concentration following fructose and lactose were calculated for comparison with other published data Intolerance was defined as an increase of >2 over baseline using a symptom score index, which was the sum of the intensities (0 = none, 1 = mild, 2 = intense) of abdominal distension or bloating, flatulence, fullness, nausea, diarrhoea, abdominal cramps, borborygmi and gastro-oesophageal reflux symptoms, which were scored hourly concurrently with the collection of the breath samples. Additional non-GI symptoms rated, but not part of the symptom index, were tiredness, diminished concentration, headache, myalgia, arthralgia, palpitations, oral aphthoid ulcers and skin rash. The choice of symptoms scored was based on the literature and the most frequent atopic and co-morbid functional disorders.
Additional methane threshold definitions for malabsorption of >3 ppm at baseline and an increase of >20 ppm over baseline at any time during the test were applied for correlations with stool patterns for comparison with previous publications. Diarrhoea was defined as loose or watery stools during >25% of bowel motions or >3 motions daily in the last 3 months. Constipation was characterised by hard, lumpy stools and increased straining during >25% of bowel motions or <3 stools per week in the last 3 months.
Dietary Protocol
The 312 patients with positive intolerance tests after May 2010 were referred to an experienced dietician (CW) for a standardised 4-week dietary adaptation, consisting of a diet low in saccharides and polyols for 1 week and subsequent weekly introduction of defined classes and amounts of fructose-, fructan-, inulin- and lactose-containing food to determine individual tolerability thresholds. Patients were maintained on the level of saccharides and polyols below their threshold of symptoms. In general, four individual sessions were scheduled with patients and questionnaires regarding abdominal symptoms, bowel and dietary habits were completed before and after the dietary modification. Symptom scoring was performed using 10-point Likert scales. Dietary compliance was checked either by direct or telephonic interview by the dietician or the gastroenterologist 6–8 weeks after initiation of the dietary changes. Compliance was considered adequate if patients confirmed that they adhered to the dietary guidelines during at least 50% of the meals consumed.
Statistics
Group differences in clinical GI and non-GI symptoms and variables were compared by Kruskall–Wallis or anova tests, as appropriate. Categorical data were compared by Chi-squared test or, if between multiple groups, by logistical regression. Correlations were analysed using the Spearman–Rank test. A significance threshold of P < 0.05 was adopted. Analysis was performed using Statistica 7.1 (StatSoft, Tulsa, OK, USA).