Table 3.
Assessment of normal gut functiona
| Assessments and parameters | Descriptions | |
|---|---|---|
| Subjective assessments of well-being | ||
| Validated questionnaires useful to assess quality of life and gut health | IBS-Quality of Life (IBS-QOL) | Validated for assessment of quality of life specific to IBS: 34 questions |
| Inflammatory Bowel Disease Questionnaire (IBDQ) | Validated for assessment of health-related quality of life (HRQoL) in adult patients with IBD | |
| Bowel Disease Questionnaire (BDQ) | Validated to distinguish patients with functional and organic GI disease | |
| Health Status Questionnaire (HSQ-12) | Validated for assessment of HRQoL in the general population | |
| Short Form Health Survey SF-12 (SF-12) | Validated for assessment of HRQoL in the general population | |
| GI symptom scores | IBS Severity Scoring System (IBS-SSS) | Validated for scoring lower GI symptoms on the basis of nine questions; range of 0 to 500 points |
| Short Form Leeds Dyspepsia Questionnaire (SF-LDQ) | Validated instrument for measuring the presence and severity of dyspepsia | |
| Gastrointestinal Symptom (GIS) profile | Validated for assessment of symptoms of functional dyspepsia; 10 questions | |
| Subject's Global Assessment of Relief (SGA) | Validated assessment of the impact of treatment on IBS-related symptoms; 1 question | |
| IBS Global Assessment of Improvement (IBS-GAI) ("adequate relief") | Asks participants if, compared to the way they felt before entering the study, their IBS symptoms have changed over the past 7 days; 1 question | |
| Functional Bowel Disorder Severity Index (FBDSI) | Validated score for assessment of patient perception of abdominal pain in IBS | |
| Numeric Rating Scale (NRS) for assessment of pain | Validated in IBS patients | |
| Visceral Sensitivity Index (VSI) | Validated psychometric instrument that measures GI symptom-specific anxiety | |
| Bristol Stool Scale/Bristol Stool Chart | A medical aid designed to classify the form of human faeces into seven categories | |
| Gastrointestinal Symptom Rating Scale | ||
| Eating habits | Food frequency questionnaire | 7-day diet history assessed using computer software |
| Objective parameters | ||
| Markers of functionality | Gastric function | pH metry in the esophagus [6,7] and stomach [1-3], gastroesophageal reflux episodes (< 50/day, <60 minutes total), viscosity of the luminal content using a viscometer, stool weight (> 100 g/d, <500 g/d) and stool consistency (water content) |
| Permeability measurements | Tracer molecules (lactulose/mannitol, 51Cr-EDTA, PEG); | |
| Motility tests | Barostat, gastric scintigraphy, 13C urea breath test (gastric emptying) and lactulose hydrogen breath test (normal range: 40 to 240 hours) | |
| Transit time | Radiopaque pellets (Hinton test) and isotope-labelled test meal (normal range: 24 to 168 hours) | |
| Digestion parameters | Stool elastase (> 200/g) and stool fat (< 7 g/d), carbohydrate breath tests, anthropometry and micronutrient analysis | |
| Markers of intestinal integrity | Epithelial integrity | Histology (villus height/crypt depth ratio, mitosis and apoptosis), mucus secretion (mucins and trefoil peptides) and Ussing chamber (ion fluxes and electric potentials) |
| Specific molecules | E-cadherin, growth factors, tight junction molecules, α1-antitrypsin in faeces and LPS in blood | |
| Antimicrobial peptides | α- and β-defensins, calprotectin, lysozyme or neutrophil-derived elastase in faeces | |
| Marker of intact immunity | Cell counts and phenotyping | Differential blood count and FACS analysis, histopathology of intestinal biopsies and immunohistochemistry of intestinal biopsies |
| Cell mediators and cytokines | Inflammatory cytokines (IL-1, IL-6 and TNFα), anti-inflammatory cytokines (IL-10 and TGFβ), regulatory cytokines (IL-2, sIL-2R, IL-4, IL-5 and so on), proteases (tryptase, chymases, chymotrypsin and so on), immunoglobulins (IgA, sIgA and IgE) and others (retinoic acid, neuropeptides and so on) | |
| Functional assays | Cell cultures and cocultures, DTH response, phagocytosis, chemotaxis, oxidative burst (superoxide anion generation) and NK cell activity | |
| Analysis of the intestinal microbiome | Classical approaches | Bacterial culture and toxin measurements |
| New approaches | Metagenomics (PCR and full bacterial sequencing), metabonomics (metabolic capacity of the microbiome) | |
aIBS, irritable bowel syndrome; IBD, inflammatory bowel disease; GI, gastrointestinal; 51CR-EDTA, chromium ethylenediaminetetraacetic acid; PEG, polyethylene glycol; LPS, lipopolysaccharide; FACS, fluorescence-activated cell sorting; IL, interleukin; TNF, tumour necrosis factor; TGF, transforming growth factor; sIL-2R, soluble interleukin 2 receptor; Ig, immunoglobulin; sIgA, secretory immunoglobulin A; DTH, delayed-type hypersensitivity; NK, natural killer; PCR, polymerase chain reaction.