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Documenting Continuum of Gut Health Measures from Health to Disease: A Review of Scientific Literature and Patient-Facing Information

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26 October 2026

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27 October 2026

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Abstract
Gut health is recognized as an important contributor to overall health, yet there is no widely accepted definition or standardized approach to its measurement. This work aimed to characterize how gut health is measured and described across academic research and patient-facing materials, and to evaluate available evidence on reliability and validity of commonly used measures. A systematic review of the literature since 2011 was conducted to identify measures of gut health used in human studies; a review of selected medical association materials was also completed to assess how gut health is communicated to in potential patient-facing materials. Measures were categorized across domains of symptoms, function, integrity, and immunity, and a targeted review of reliability and validity of the different tools and measurements identified from the systematic literature review was performed. Substantial heterogeneity in how gut health is conceptualized and measured was observed and gut health was rarely defined. While a broad range of tools and measurements are available and there is good evidence for their overall reliability and validity, there is a lack of evidence supporting their reliability and validity specific to gut health. This review provides a foundation for identifying candidate measures and gaps in validation for defining gut health.
Keywords: 
gut health
;  
systematic review
;  
measurement reliability
;  
measurement validity
;  
biomarkers
Subject: 
Medicine and Pharmacology  -   Gastroenterology and Hepatology

Introduction

There is not a clear definition for the term “gut health”. Bischoff (2011) proposes that one might define optimal gut health as “a state of physical and mental well-being in the absence of GI complaints that require the consultation of a doctor, in the absence of indications of or risks for bowel disease and in the absence of confirmed bowel disease” [1]. The gut is an important contributor to health and has relationships beyond the immediate bowel, including impacts on overall immune function [2], neurological conditions [3,4], metabolic conditions [5], and endocrine function [6]. Recently, the International Scientific Association for Probiotics and Prebiotics (ISAPP) issued a consensus statement on the definition and scope of gut health, proposing a definition of gut health as “a state of normal gastrointestinal function without gastrointestinal disease and gut-related symptoms that affect quality of life” [7]. As noted by others, this creates an important foundation for continuing to define gut health, but there is a continued need to evolve and refine this definition based on utility in clinical or policy settings, and a need to incorporate key risk factors or prevalent digestive diseases, or influence of societal factors [8]. Bischoff (2011) further summarized five criteria for a healthy gut: effective digestion and absorption of food, absence of gastrointestinal illness, normal and stable intestinal microbiota, effective immune status, and status of well-being [1]. Each of these areas has specific signs of optimal gastrointestinal health; however, despite what is known about the importance of the gut for overall health, there is not a clear consensus of what are the effective measurements of gut health or how well results from studies using different measurements can be compared.
Subjective and objective measures of gut health currently exist and have varying degrees of reliability and validity [1]. Subjective measures, which rely on research participant or patient self-report of gut health, focus on quality of life, presence of bowel disease, GI symptoms or eating habits [1,9,10,11,12,13,14,15,16,17]. There are varying extents to which these questionnaires or diaries were developed for use in healthy populations or populations with existing gastrointestinal diseases or conditions. For example, several questionnaires are validated for use in patients with dyspepsia [10,11] or irritable bowel syndrome [12,13,14,15,16,17]. Objective measures, which are biomarkers independent of self-report, have generally focused on markers of functionality, intestinal integrity, intact immunity, or the gut microbiome [1,14,18,19]. While having markers of gut health that do not rely on self-report could provide more consistency in measurements, challenges of objective markers include scale to large human studies due to difficulty in collecting stool samples, lack of specificity for gut health of non-stool biomarkers, and lack of a definition of an optimal or normal microbiome for microbiome assessment. And, in the past fifteen years since Bischoff provided a seminal assessment of gut health measures [1], additional measures of gut health have entered research [20,21].
When research studies use differing measurements, it becomes challenging to compare results, and lack of consensus regarding the value of each assessment tool hinders appropriate communication with patients and consumers about research results. It also means that there can be an influx of products to market, such as at-home microbiome testing kits, that offer numerous results for patients but for which research has not yet come to a consensus about associations with gut or overall health. For example, it has been acknowledged that a limitation of microbiome testing is that it should not be used as a diagnostic tool for any health condition [22]. To move the research field ahead and provide translational and actionable evidence for patients and consumers, there is a need to understand and agree on the concept of gut health. A key step is to characterize available measures and how these measures are used and interpreted in both academic and patient literature. This paper describes a series of work was undertaken to evaluate (1) which measures and indicators of gut health, and for what diseases and health states, are being used in academic and healthcare research (2) which measures and indicators of gut health, and for what diseases and health states, are being used by medical societies, and (3) what is known about the reliability and validity of commonly used measures and indicators of gut health. For each of these areas, the methods and are presented separately, with an overall discussion and conclusion provided across the three areas of work.

Measures and Indicators of Gut Health Being Used in Academic Research

Methods for Measures and Indicators of Gut Health in Academic Research
A systematic review was undertaken to evaluate measures and indicators of gut health in academic literature. Pre-registration of the review was done on Open Science Framework (OSF) (https://osf.io/trjud/overview). The search strategy was developed to capture broad area of gut health that include known features (permeability, function, and symptoms) and different terminology that can be used to classify the gut (gut, gastrointestinal, intestinal, and gastric). To place emphasis on these terms as part of the research work, they were included terms to be searched in titles for both PubMed and EMBASE. Publications were limited to January 1, 2010 to present to capture work that has been done since the review by Bischoff et al. (2011) [1].
PubMed and EMBASE databases were searched for publications from January 1, 2010 through June 11, 2024. The inclusion and exclusion criteria were:
Inclusion Criteria
  • Population: any human population, no geographic restrictions
  • Exposure (or outcome): objectively or subjectively measured gut health
  • Comparison: N/A
  • Outcome (or exposure): objectively or subjectively measured gut health
  • Study design: trials or observational studies, case series with n≥20
  • Other:
  • o Publication date on or after January 1, 2010
  • o English language
Exclusion Criteria
  • Population: non-human research
  • Exposure (or outcome): no indication of how gut health was measured, studies of microbiome (or other -omics) only
  • Comparison: no restrictions
  • Outcomes (or exposure): no indication of how gut health was measured, studies of microbiome (or other -omics) only
  • Study design: case reports or case series with n<20, opinion pieces, reviews
  • Other:
  • o Publication date before January 1, 2010
  • o Not in English
  • o Conference abstracts
The query strings utilized for each of PubMed and EMBASE were:
PubMed:
“gut health”[title] OR “gut permeability”[title] OR “gut function”[title] OR “gut symptoms”[title] OR “gastrointestinal health”[title/abstract] OR “gastrointestinal permeability”[title] OR “gastrointestinal function”[title] OR “gastrointestinal symptoms”[title] OR “gastric health”[title] OR “gastric permeability”[title] OR “gastric function”[title] OR “gastric symptoms”[title] OR “intestinal health”[title] OR “intestinal permeability”[title] OR “intestinal function”[title] OR “intestinal symptoms”[title]
Filters applied: English, Humans, from 2010/1/1 - 3000/12/12
EMBASE:
‘human’/mj AND (‘gut health’:ti OR ‘gut permeability’:ti OR ‘gut function’:ti OR ‘gut symptoms’:ti OR ‘gastrointestinal health’:ti OR ‘gastrointestinal permeability’:ti OR ‘gastrointestinal function’:ti OR ‘gastrointestinal symptoms’:ti OR ‘gastric health’:ti OR ‘gastric permeability’:ti OR ‘gastric function’:ti OR ‘gastric symptoms’:ti OR ‘intestinal health’:ti OR ‘intestinal permeability’:ti OR ‘intestinal function’:ti OR ‘intestinal symptoms’:ti) AND [2010-2024]/py
De-duplication was conducted using EndNote reference manager. The final set of references was imported into DistillerSR for review. The screening was conducted in two phases: title/abstract and full-text. At the title/abstract phase, studies were included/excluded if they appear to meet the inclusion/exclusion criteria. Each reference was initially screened by one person. At the full-text phase, each full-text was reviewed by one individual for include/exclude decision. Late-stage exclusions were made at the time of data extraction if needed. At the full-text stage, select information was extracted (gut health measurement area and whether outcomes are immediately post-operative). All screening stages were completed by humans and no AI was utilized.
After the initial abstract and full-text review, it became apparent the volume of literature was larger than possible to review within the scope of the planned project. After consultation with the Institute for the Advancement of Food and Nutrition Sciences Nutrition for Gut Health Committee, the scope of review was reduced to 240 articles for full-text data abstraction. In the initial screening, information about categories of measures (symptoms, functionality, integrity, inflammation) were recorded for each paper. A prioritization strategy was developed that maximized representation across preliminary categories of inflammation (priority 1), intestinal integrity (priority 2), functionality (priority 3), and symptoms. Papers were selected that represented the most recent papers in the inflammation categories for 60 manuscripts (if they overlapped other categories, they were removed from the pool), then integrity, etc., until 240 manuscripts were selected.
Data abstraction was conducted by a single reviewer, and the final spreadsheet was checked for completeness by a second reviewer. The following information was abstracted:
-
Design
-
o Pre-specified categories: randomized controlled trial, non-randomized trial, cohort, case-control, cross-sectional, other
-
Population characteristics
-
o Age ranges: any, children only (under 18 years of age), adults only (18+ years of age)
-
o Gender/sex: any, males only, females only
-
o Geographic location: specific country or multi-country
-
o Study population size
-
Disease or health state studied (pre-specified categories)
-
Disease or health state studied (general text description)
-
Subjective and objective measures of gut health utilized
-
o Pre-specified categories: function, permeability, symptoms, other
-
o Subjective and objective measures of gut health utilized (general text description)
Geographic locations and subjective and objective measures of gut health were reviewed for consistency and transformed to a consistent data value, e.g., “US”, “U.S.”, and “United States” were transformed to “United States”. Re-coding was done in statistical software for reproducibility and transparency, and statistical code is available on OSF.
Results for Measures and Indicators of Gut Health in Academic Research
A third of the studies were randomized controlled trials (n=80, 33.3%), with the remainder of studies with cohort (n=60, 25%), cross-sectional (n=60, 25%), case-control (n=31, n=12.9%), or other (n=9, 3.7%). Most the studies were in adults only (n=175, 72.9%), compared to children only (n=56, 23.3%) or across all ages (n=8, 3.3%). Most studies were conducted in any or all sexes (n=211, 87.9%) and located in a single country (n=228, 95.0%). A list of the health conditions or diseases studied in the papers is provided in Table 1.
Many studies included more than one measure or assessment, and a study could be represented more than once across a category of symptoms, function, integrity, or immunity. There were 135 studies including symptom measures that spanned 2023-2024, 44 studies for function that spanned 2023-2024, 109 studies for integrity that spanned 2021-2024, and 98 studies that spanned 2021-2024. Because the initial classification was based on the authors description of their tool/measure, some measures of functionality were ultimately re-classified later (often to symptoms), and there were fewer studies of function available. There were 60 unique tools or methods identified in the 135 studies for symptoms (Supplemental Table S1a), and the five most frequently cited were the Gastrointestinal Symptom Rating Scale; symptoms, not otherwise specified; Bristol Stool Scale; a visual analog scale questionnaire, not other specified or described; and, the electronic medical record. There were 26 unique tools or methods identified in the 44 studies for function (Supplemental Table S1b), and the five most frequently cited were the time to first flatus; time to first bowel movement; gastric emptying study; bowel sound; and, gastrin. There were 22 unique tools or methods identified in the 109 studies of integrity (Supplemental Table S1c), and the five most frequently cited were zonulin; lactulose and mannitol, or lactulose-mannitol ratio; lipopolysaccharide or lipopolysaccharide binding protein; intestinal fatty-acid binding protein; and, endoscopic evaluation. There were 21 unique tools and methods identified for the 98 studies of immunity (Supplemental Table S1d), and the five most frequently cited were cytokines; calprotectin; C-reactive protein; inflammatory biomarkers; and, immunoglobulins.
Measures and Indicators of Gut Health Being Used to Communicate with Patients
Methods for Measures and Indicators in Communication with Patients
Based on the results from the systematic literature review, the most frequent diseases or health states were identified. Medical association specialties that covered the identified disease states were identified and targeted for further information about gut health, in terms of position statements, guidance documents, or patient-facing materials. To identify medical association specialties, the medical societies that make up the Federation of Medicine (https://www.ama-assn.org/house-delegates/hod-organization/member-organizations-ama-house-delegates) were evaluated for inclusion.
Selected medical association websites were searched for relevant position statements and guidance documents, and these were downloaded for review and abstraction of relevant information. Searches focused on “gut health”, “intestinal health”, and “gastrointestinal health”. Duplicative topics (e.g., updated statements) prioritized the most recent publication. After removal of duplicative topics (e.g., updated statements), the most recent publications will be given priority of the non-duplicative topics. Statements that solely focused on the gut microbiome or microbiota were excluded; however, statements that broadly focus on gut health but include mention of the microbiome were included. An initial list of available statements will be generated, and a single reviewer identified statements and documents for inclusion. The following a priori information was abstracted from the position statements and guidance documents: Publishing medical association specialty; title of document; date of last update for document; target population for the information (e.g., clinicians, patients); objective of the statement; definition of gut health (if provided); mention of any specific measures of gut health; and, additional associated topics (e.g., medications, nutrition, surgery). All abstractions were conducted by a single reviewer, and a secondary reviewer checked the final abstraction spreadsheet for completeness. Detailed abstraction spreadsheets for this work are available on Open Science Framework (link will be made available upon publication acceptance; provided as supplemental material for manuscript review).
Results for Measures and Indicators in Communication with Patients
Twenty medical associations from the Federation of Medicine were included based on either being general medical associations or potentially relevant specialty associations (Supplemental Table S2). Based on the disease states identified from the systematic literature review, relevant specialties targeted included endocrinology, gastroenterology, immunology or infectious disease, neurology, obesity, oncology, pediatrics, psychiatry, rheumatology, and surgery. Seven of these associations did not have relevant websites using the gut health, intestinal health, or gastrointestinal health as search terms. The number of websites included in the other thirteen associations ranges from one (American Academy of Family Physicians) or 21 (American Academy of Pediatrics).
The key characteristics represented in the websites are represented in Table 2. Most websites were focused on patients and very few gave a definition of gut health. Pediatrics was highly represented due to the linkage of the American Association of Pediatrics directly with healthychildren.org. Gut Health was commonly presented with other topics such as other health conditions, diet, medications, microbiome, infections, or sleep.
Evaluation of Reliability and Validity of Commonly Used Measures of Gut Health
Methods for Evaluation of Reliability and Validity
The evaluation of reliability and validity built upon the systematic literature review undertaken to evaluate the measures and indicators of gut health. The measures and indicators identified were the starting point for the measures considered. An additional review of the literature of reliability and validity was conducted on selected measures. To be included in the review of reliability and validity, the measure needed to be specific enough and referenced in at least two studies from the systematic literature review conducted. Examples of non-specific measures included studies that noted measuring symptoms with self-report means (e.g., surveys, diaries) without sufficient other details to validate, author-developed questionnaires or surveys without details, or utilizing electronic health records without further specification.
The 240 papers that were included in the systematic literature review were re-reviewed for references to reliability or validity of the measure included. These referenced were automatically included in this evaluation. In addition to these references, a PubMed search was conducted to identify additional reliability and validity references to include. There were three initial tiers of searches considered for each of the measures included. The basic structure of each of those tiers were:
Tier 1: Broad search: “measure name”[title/abstract] AND (reliability[title/abstract] OR validity[title/abstract])”
Tier 2: Narrowed search: “measure name”[title/abstract] AND (reliability[title/abstract] OR validity[title/abstract]) AND (gut[title/abstract] OR gastrointestinal[title/abstract])”
Tier 3: Narrowest search: “measure name”[title] AND (reliability[title] OR validity[title])”
A fourth tier was conducted for select number of results that additional refinement from the narrowest search due to the high number of observations returned. These were limited to the Rome III, Rome IV, and SF-36, and likely because these questionnaires are commonly used outside of gut health. A list of which tier was used for each measurement is provided in Table 3.
Tier 4: Refined narrowest search: “measure name”[title] AND (reliability[title/abstract] OR validity[title/abstract]) AND (gut[title/abstract] OR gastrointestinal[title/abstract]).
Results for Evaluation of Reliability and Validity
Of the 129 unique measurements identified from the systematic literature review, 53 (41.1%) were included in the evaluation of reliability and validity (Table 3): 16 for symptoms (26.7%), 10 for function (38.5%), 12 for integrity (54.6%), and 15 for immunity (71.4%). For the measurements or tools that were excluded, most were excluded because too few studies were included (n=62) rather than being non-specific (n=14) (Supplemental Table S3).
At the initial review stage, there were 300 articles reviewed, in the following categories: symptoms (n=58), function (n=35), integrity (n=58), and immunity (n=108). Of these 300 articles, 95 were included for full text extraction. Reasons that article was not included in the full text extraction included: not an evaluation of the measurement or tool specifically (n=102), not an evaluation of symptoms category as GI symptoms (n=17), not an evaluation of the other categories (n=43), non-human study (n=18), not in English (n=13), abstract only (n=6), no reliability or validity results were present (n=2), repeat of another article in the list (n=3), or not a research article (n=1).
For symptoms studies, many studies conducted internal consistency evaluations and test-retest to evaluate reliability (Table 3). The most common comparison was to the SF-36 when evaluating validity. For function studies, reliability was not commonly measured, and validity was commonly evaluated as a comparison to visual methods (e.g., ultrasound). For both integrity and immunity, reliability was not commonly measured, and, while sugar tests were more common than some other comparisons for gut integrity, there was no clear gold standard for gut integrity or gut immunity. Detailed abstraction spreadsheets for this work are available on Open Science Framework (link will be made available upon publication acceptance; provided as supplemental material for manuscript review).
Discussion
Gut health is rarely defined in research studies or medical association websites that involved aspects of gut health. Even though gut health was a term used to search for research articles, this term was rarely defined in research articles, even when it was a major topic of the work. This may coincide with gut health being a feature of specific conditions or diseases rather than a concept itself within the research literature and may be a result of a lack of clear consensus definition for gut health. That could have been a foundation for the parent work in the Bischoff (2011) review that proposed that one might define optimal gut health primarily as a state in that had an absence of GI disease or complaints [1]. More recently, this has been expanded by ISAPP to focus on function without disease and symptoms that quality of life [7]. Even with the ISAPP consensus definition, there is debate about the need for more in this area. This is an important conversation because context does matter, and research and clinical practice will be important different contexts. It has been highlighted that what can be used in research vs. clinical practice may not be same, and as has been emphasized elsewhere, the importance of the research question when selecting a tool for the microbiome assessment is essential [23]. Furthermore, what is important to patients vs. what is important to researchers may also not be the same. For example, a researcher may have a need for a sensitive biomarker, whereas a patient may be more concerned with changes in a quality-of-life measure.
Thus, gut health research is methodologically diverse with no single dominant or standardized approach across domains, and it may remain this way. In the systematic literature review, there were 129 unique measurements or tools in the 240 studies, with substantial heterogeneity in the pre-defined domains of symptoms, function, integrity, and immunity, and many of the studies used multiple measures. However, this may reflect the design of the systematic literature review. Gut health was not specifically the exposure or outcome for the review and may have even been a covariate in some studies. Thus, the reason for the study of gut health was not the same across studies, which would be expected to influence how gut health was being measured. Given the recently proposed definition by ISAPP [7], future work could build upon this work on measurements and tools that are specifically targeted to measure gut health as an outcome in pre-defined populations to provide a narrower scope on the measurements or tools being used.
Review of materials from medical associations showed that few patient-facing resources provided a clear definition of gut health, even when gut health was discussed. Content frequently linked gut health to other topics (e.g., diet, microbiome, medications, sleep) but rarely referenced specific measures or indicators.
However, there are a wide variety of measurements or tools that are available and used to evaluate aspects of gut health in academic research. While many of these tools appear to have been assessed for reliability and validity generally, evaluation of these measurements and tools specific to gut health is not as extensive, and this is an area where future work could be beneficial to the field. The most common comparison for validity for symptoms was often done with comparison to the SF-36 questionnaire, which includes a limited set of physical functioning questions that are not gut health specific but rather measure overall physical function. Developing a clear consensus on the gold standard for the gut health symptoms comparison measure would aid in validation studies. For objective biomarkers, there is also a clear need for more validation studies in the context of gut health, as there were fewer studies that were included in full text extraction after the initial review. This is an important consideration because these tools may have different sensitivity and specificity in populations with gut health-related conditions.
Microbiome was not considered as part of the scope of this work. However, the microbiome maybe an important consideration in how individuals view gut health. For example, probiotics and prebiotics are common interventions leveraged to reduce symptoms or relieve functional bowel disorders [24]. The microbiome was a consideration in the definition for ISAPP, and the panel incorporated aspects of defining of a healthy gut microbiome or dysbiosis as part of their consensus statement. The microbiome is a challenging aspect to consider for gut health, because there is substantial interindividual variability in the gut microbiomes across healthy individuals and most of the variability in the microbiome is yet to be explained [25]. As noted [7,8], the microbiome will continue to be an important part of research in gut health, however measurement for clinical practice cannot be practically implemented at this time.

Conclusions

This work provides a foundational overview of how gut health has been measured, characterized, and communicated across academic research and select patient-facing materials. By systematically cataloging measures used in research, reviewing how gut health is presented by medical associations, and evaluating available evidence on reliability and validity, this effort establishes an initial framework for understanding the current landscape rather than providing a comprehensive or definitive inventory. While the review did not capture all the literature due to vast size, it is unlikely that major categories of measures have been omitted, and it provides good representativeness, relative importance, or appropriateness of specific tools across populations and contexts. The findings underscore that gut health remains an evolving concept, with no single, stable definition adopted consistently across research or clinical communication. As scientific understanding advances and perspectives on health broaden beyond disease absence, it is likely that definitions of gut health, and the measures used to assess it, will continue to evolve. This heterogeneity reinforces the need for a variety of complementary subjective and objective assessments, selected based on the research question, clinical context, and population of interest rather than reliance on a single measure or domain. If future efforts seek to translate gut health research into meaningful patient communication or decision-making, this review provides a foundation for identifying candidate measures and gaps in validation.

Supplementary Materials

The following supporting information can be downloaded at the website of this paper posted on Preprints.org. Supplemental Table S1. Unique tools and measurements identified in studies that evaluated symptoms (a), function (b), gut integrity (c), and immunity (d); Table S2. Relevant general and specialty medical associations considered for the website review from the Federation of the Medicine; Supplemental Table S3. Inclusion and Exclusion of Tools and Measurements for Reliability and Validity Evaluation.

Acknowledgments

No generative AI was used in the generation of this work or writing of the manuscript.

Conflicts of Interest

The authors are employees of EpidStrategies, A BlueRidge Life Sciences Company. This work was supported by the Institute for the Advancement of Food and Nutrition Sciences (IAFNS). IAFNS is a nonprofit science organization that pools funding from industry and advances science through the in-kind and financial contributions from private and public sector members. The IAFNS Gut Health Committee was involved in the initial conceptualization of the work and provided feedback on a reduction in scope, but was not involved in the data collection, analysis, or preparation of the manuscript.

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Table 1. Health States and Disease Conditions Represented in the Articles Included in the Systematic Literature Review.
Table 1. Health States and Disease Conditions Represented in the Articles Included in the Systematic Literature Review.
Health State or Disease Condition N (%)
Healthy only 59 (24.6%)
Gastrointestinal disorders or diseases 50 (20.8%)
Mental health or neurological 24 (10.0%)
Metabolic (e.g., diabetes, severe/morbid obesity) 23 (9.6%)
Neoplasms 21 (8.8%)
Infectious 18 (7.5%)
Autoimmune 14 (5.8%)
Other (e.g., cystic fibrosis, critical ICU patients, patients with sepsis) 9 (3.8%)
Gynecologic conditions 5 (2.1%)
Renal 5 (2.1%)
Cardiovascular or cardiometabolic 4 (1.7%)
Orthopedic 4 (1.7%)
Multiple diseases 3 (1.2%)
Respiratory (e.g., asthma) 1 (0.4%)
Table 2. Key Website Characteristics from the Evaluation of Gut Health Related Web Content from Selected Federation of Medicine Associations’ Websites.
Table 2. Key Website Characteristics from the Evaluation of Gut Health Related Web Content from Selected Federation of Medicine Associations’ Websites.
Characteristics n of websites included in data abstraction (%)
Target Audience
Clinicians/practitioners 27 (39.7%)
Patients 39 (57.4%)
Unclear 2 (2.9%)
Include a definition or description of “gut health”
Yes 3 (4.4%)
No 65 (95.6%)
Associated Topics
Other Health Conditions 41 (60.3%)
Diet 33 (48.5%)
Medications 24 (35.3%)
Microbiome 23 (33.8%)
Infection 18 (26.5%)
Sleep 5 (7.4%)
Medical Specialty
Family medicine 1 (1.5%)
Gastroenterology 5 (7.4%)
General 4 (5.9%)
Immunology 3 (4.4%)
Infectious disease 9 (13.2%)
Obesity 8 (11.8%)
Oncology 2 (2.9%)
Pediatrics 21 (30.9%)
Rheumatology 4 (5.9%)
Surgery 9 (13.2%)
Women’s health 2 (2.9%)
Table 3. Characteristics of Studies Included in the Data Extraction for Reliability and Validity Evaluation of Measurements and Tools from the Systematic Literature Review.
Table 3. Characteristics of Studies Included in the Data Extraction for Reliability and Validity Evaluation of Measurements and Tools from the Systematic Literature Review.
Category Measurement Search Criteria Tier Used Number of Studies Included in Initial Review Number of Studies Included in Extraction Reliability Studies Validity Studies
Symptoms Bristol Stool Scale Tier 2 8 5 1 study evaluated reliability in children 4 studies evaluated validity - each had to a different comparator: patient vs. expert evaluation, BSS vs. stool water, BSS vs. whole-gut transit time, BSS vs. Pediatric Rome III scale
Symptoms European Organisation for Research and Treatment of Cancer Questionnaire Tier 2 11 4 3 studies evaluated internal consistency in the questionnaire and 1 study evaluated test-retest reliability 1 study evaluated convergent and divergent validity compared to various scales of the EORTC QLQ-C30, and 1 study compared to the Gastrointestinal Quality of Life Index
Symptoms Gastrointestinal Quality of Life Index (GIQLI) Questionnaire Tier 4 9 8 Seven studies evaluated internal consistency and five studies evaluated test-retest reliability over varying amounts of time 1 study evaluated construct validity, and other studies compared to various other questionnaires: SF-36 (n=4), RSCL (n=1), WHO-BREF (n=1), GSRS (n=1), EORTC (n=1)
Symptoms Gastrointestinal Symptom Rating Scale Tier 4 18 9 Nine studies evaluated internal consistency and nine studies evaluated test-retest reliability over varying amounts of time Two studies evaluated construct validity, and other studies compared to various other questionnaires: SF-36 (n=6) and HQRL (n=1). 1 study compared to a diary.
Symptoms Gastroparesis Cardinal Symptom Index (GCSI) Tier 2 2 2 2 studies evaluated internal reliability, and 1 study also evaluated test-retest reliability. 1 study compared GCSI to SF-36 and disability days, and also evaluated construct validity.
Symptoms Generalized Anxiety Disorder-7 questionnaire Tier 2 3 0 --- ---
Symptoms I-FEED Tier 2 2 1 0 studies evaluated reliability Evaluated construct validity
Symptoms IBS-Severity Scoring System Tier 2 2 2 1 study evaluated scores repeated in 24 hours 1 study compared IBS-SSS vs. experience sampling method
Symptoms Patient Assessment of Constipation Symptoms (PAC-SYM) questionnaire Tier 1 4 1 1 study evaluated internal concurrent reliability 1 study compared to SF-36
Symptoms Patient Health Questionnaire-15 Tier 2 7 1 1 study evaluated internal consistency 1 study evaluated construct validity and compared to PHQ-9 and FGI-checklist
Symptoms Patient Health Questionnaire-9 Tier 2 6 2 1 study evaluated internal consistency and test-retest 1 study evaluated content validity and 1 study compared PHQ-9 to the GSRS
Symptoms Pediatric Quality of Life questionnaire Tier 2 9 5 4 studies evaluated internal consistency and 1 study evaluated test-retest reliability Five studies evaluated validity of patient-parent reporting. Three studies evaluated construct validity of scales.
Symptoms Perceived Stress Scale Tier 2 3 1 1 study evaluated internal consistency 1 study compared to SHC subscales and the CHIPS factors
Symptoms Rome III criteria Tier 4 7 3 0 studies evaluated reliability 1 study compared to weekly questionnaires of somatic symptoms and 2 studies compared to diagnosis of disease (predictive value)
Symptoms Rome IV criteria Tier 4 6 4 1 study evaluated test-retest reliability 3 studies compared to diagnosis of disease (predictive value)
Symptoms SF-36 questionnaire Tier 4 2 1 1 study evaluated internal consistency 1 study evaluated for concurrent validity against total bowel symptom score
Function Anorectal manometry Tier 3 3 1 1 study evaluated inter-rater reliability 1 study compared to diagnosis of disease (predictive value)
Function Bowel sounds Tier 2 6 1 1 study evaluated inter-rater reliability 1 study compared to diagnosis of small bowel obstruction or post-operative ileus (predictive value)
Function Ectrogastrography for gastric pacing Tier 2 6 0 --- ---
Function Gastric emptying study Tier 1 2 2 0 studies evaluated reliability 1 study compared 13C-acetate breath test to MRI, and 1 study compared 13C-acetate breath test to γ-scintigraphy and ultrasonography
Function Gastrin Tier 2 8 1 0 studies evaluated reliability 1 study compared to diagnosis of disease (predictive value)
Function Motilin Tier 2 2 0 --- ---
Function Motility capsule Tier 2 2 1 1 study evaluated inter-rater reliability 1 study compared to gastric emptying scintigraphy
Function Somatostatin Tier 2 2 0 --- ---
Function Time to first bowel movement Tier 1 1 0 --- ---
Function Time to first flatus Tier 2 3 0 --- ---
Integrity Alpha-1-antitrypsin Tier 2 8 6 0 studies evaluated reliability 4 studies evaluated fecal protein less, 1 study compared to lactulose:mannitol ratio, and 1 study compared to diagnosis of disease (predictive value)
Integrity Claudin Tier 2 3 1 1 study evaluated test-retest reliability 0 studies evaluated validity
Integrity Diamine oxidase Tier 1 4 1 0 studies evaluated reliability 1 study compared to diagnosis of disease (predictive value)
Integrity Endoscopic evaluation Tier 2 5 0 --- ---
Integrity Glucagon-like peptides Tier 2 7 1 1 study compared values six months apart 0 studies evaluated validity
Integrity Intestinal fatty-acid binding protein Tier 2 2 2 2 studies evaluated test-retest reliability 0 studies evaluated validity
Integrity Lactulose and mannitol, or lactulose-mannitol ratio Tier 2 8 4 2 studies evaluated multiple measurements within 1-day period 1 study compared to endocab IgM levels, and 1 study compared to gluten immunogenic peptides
Integrity Lactulose and rhamnose, or lactulose-rhamnose ratio Tier 2 4 2 1 study evaluated multiple measurements within 1-day period 1 study compared to classical dual sugar and multi-sugar test
Integrity Lipopolysaccharide or lipopolysaccharide binding protein (LBP) Tier 2 5 2 2 studies evaluated test-retest reliability 0 studies evaluated validity
Integrity Sucralose-erythritol ratio Tier 2 3 1 0 studies evaluated reliability 1 study compared to classical dual sugar and multi-sugar test
Integrity Sucrose recovery Tier 2 3 1 0 studies evaluated reliability 1 study compared to classical dual sugar and multi-sugar test
Integrity Xonulin Tier 2 6 1 0 studies evaluated reliability 1 study compared to lactulose-mannitol ratio test
Immunity Antibodies or autoantibodies (specifically IgA) Tier 2 14 1 0 studies evaluated reliability 1 study compared to diagnosis of disease (predictive value)
Immunity Breath hydrogen for SIBO Tier 2 7 1 1 study evaluated test-retest reliability 1 study compared to symptoms
Immunity C-reactive protein Tier 2 13 1 0 studies evaluated reliability 1 study compared to fecal calprotectin
Immunity Calprotectin Tier 2 16 5 0 studies evaluated reliability 3 studies compared to diagnosis of disease (predictive value), 1 study compared to erthocyte sedimentation rate, and 1 study compared to lactulose-mannitol rato
Immunity Cytokines Tier 2 12 1 1 study evaluated test-retest reliability 0 studies evaluated validity
Immunity Endotoxins or endotoxemia Tier 2 8 2 2 studies evaluated test-retest reliability 0 studies evaluated validity
Immunity Glycoprotein Tier 2 7 0 --- ---
Immunity Human beta-defensin-2 Tier 1 2 0 --- ---
Immunity immunoglobulins Tier 2 14 1 0 studies evaluated reliability 1 study compared plasma and dried blood spots
Immunity Inflammatory biomarkers (e.g., lymphocytes, Th17, CD4, TLR, blood cell Tier 2 4 1 0 studies evaluated reliability 1 study compared to fecal high mobility group box 1
Immunity Lactoferrin Tier 2 1 0 --- ---
Immunity Myeloperoxidase Tier 2 1 0 --- ---
Immunity Neopterin Tier 3 3 1 0 studies evaluated reliability 1 study compared to endoscopic scores and diagnosis of disease (predictive value)
Immunity S100A12 or S100 calcium- binding protein A8 or S100β Tier 2 1 0 --- ---
Immunity WBCs and eosinophils Tier 2 3 0 --- ---
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