Empirically derived symptom sub-groups correspond poorly with diagnostic criteria for functional dyspepsia and irritable bowel syndrome. A factor and cluster analysis of a patient sample

Unsupervised machine learning highlights the challenges of subtyping disorders of gut-brain interaction

BACKGROUND

Unsupervised machine learning describes a collection of powerful techniques that seek to identify hidden patterns in unlabeled data. These techniques can be broadly categorized into dimension reduction, which transforms and combines the original set of measurements to simplify data, and cluster analysis, which seeks to group subjects based on some measure of similarity. Unsupervised machine learning can be used to explore alternative subtyping of disorders of gut-brain interaction (DGBI) compared to the existing gastrointestinal symptom-based definitions of Rome IV.

PURPOSE

This present review aims to familiarize the reader with fundamental concepts of unsupervised machine learning using accessible definitions and provide a critical summary of their application to the evaluation of DGBI subtyping. By considering the overlap between Rome IV clinical definitions and identified clusters, along with clinical and physiological insights, this paper speculates on the possible implications for DGBI. Also considered are algorithmic developments in the unsupervised machine learning community that may help leverage increasingly available omics data to explore biologically informed definitions. Unsupervised machine learning challenges the modern subtyping of DGBI and, with the necessary clinical validation, has the potential to enhance future iterations of the Rome criteria to identify more homogeneous, diagnosable, and treatable patient populations.

Subtyping irritable bowel syndrome using cluster analysis: a systematic review

BACKGROUND

Irritable bowel syndrome (IBS) is a common chronic functional gastrointestinal disorder associated with a wide range of clinical symptoms. Some researchers have used cluster analysis (CA), a group of non-supervised learning methods that identifies homogenous clusters within different entities based on their similarity.

OBJECTIVE AND METHODS

This literature review aims to identify published articles that apply CA to IBS patients. We searched relevant keywords in PubMed, Embase, Web of Science, and Scopus. We reviewed studies in terms of the selected variables, participants' characteristics, data collection, methodology, number of clusters, clusters' profiles, and results.

RESULTS

Among the 14 articles focused on the heterogeneity of IBS, eight of them utilized K-means Cluster Analysis (K-means CA), four employed Hierarchical Cluster Analysis, and only two studies utilized Latent Class Analysis. Seven studies focused on clinical symptoms, while four articles examined anocolorectal functions. Two studies were centered around immunological findings, and only one study explored microbial composition. The number of clusters obtained ranged from two to seven, showing variation across the studies. Males exhibited lower symptom severity and fewer psychological findings. The association between symptom severity and rectal perception suggests that altered rectal perception serves as a biological indicator of IBS. Ultra-slow waves observed in IBS patients are linked to increased activity of the anal sphincter, higher anal pressure, dystonia, and dyschezia.

CONCLUSION

IBS has different subgroups based on different factors. Most IBS patients have low clinical severity, good QoL, high rectal sensitivity, delayed left colon transit time, increased systemic cytokines, and changes in microbial composition, including increased Firmicutes-associated taxa and depleted Bacteroidetes-related taxa. However, the number of clusters is inconsistent across studies due to the methodological heterogeneity. CA, a valuable non-supervised learning method, is sensitive to hyperparameters like the number of clusters and random initialization of cluster centers. The random nature of these parameters leads to diverse outcomes even with the same algorithm. This has implications for future research and practical applications, necessitating further studies to improve our understanding of IBS and develop personalized treatments.

Clusters of community-dwelling individuals empirically derived from stool diaries correspond with clinically meaningful outcomes

BACKGROUND

Functional gastrointestinal disorders (FGIDs) are diagnosed according to expert consensus criteria based on recall of symptoms over periods of 3 months or longer. Whether the expert opinion concords with underlying disease process and whether individual recall is accurate are both in doubt. This study aimed to identify naturally occurring clusters of individuals with respect to symptom pattern, evaluate their significance, compare cluster profiles with expert opinion and evaluate their temporal stability.

METHODS

As part of a random population study of FGID-related symptoms, we first explored the use of prospective stool and symptom diaries combined with empirical grouping of individuals into clusters using nonhierarchical cluster analysis.

RESULTS

The analysis identified two clusters of individuals, one of which was characterized by elevated scores on all domains of symptoms (26% of the sample) and one that was low to average on all domains (74% of the sample). Cluster membership was found to be stable over a long interval. Clusters were found to differ on most domains of quality-of-life (d = 0.46-0.74), self-rated health (d = -0.42) and depression (d = -0.42) but not anxiety. Prevalence of clinically diagnosed irritable bowel syndrome (IBS) was higher in the more impacted cluster (33%) compared with the healthy cluster (13%; P < 0.0001).

CONCLUSION

A naturalistic classification of individuals challenges consensus criteria in showing that some IBS individuals have a symptom experience not unlike health. The proposed approach has demonstrated temporal stability over time, unlike consensus criteria. A naturalistic disease classification system may have practical advantages over consensus criteria when supported by a decision-analytic system.

Identification and validation of functional gastrointestinal disorder subtypes using latent class analysis: a population-based study

OBJECTIVE

Attempts to categorize distinct functional gastrointestinal disorders based on reported symptoms continue but symptoms frequently overlap. The study objective was to use latent class analysis (LCA) which accommodates both continuous and discrete manifest variables to determine mutually exclusive subgroup assignments of a population-based sample using gastrointestinal symptom and patient data.

MATERIALS AND METHODS

A validated bowel disease questionnaire and somatic symptom questionnaire were mailed to an age and gender stratified randomly selected community sample. Responses to the symptom questions were dichotomized as frequent vs. infrequent based on Rome IV criteria. A LCA model was developed using a calibration subset and the results applied to the validation subset.

RESULTS

There were 3831 total respondents (48%) with 3425 having complete data. The LCA algorithm was run for each of 10 (random) splits of the dataset and 2-6 latent classes were specified. Using the values of Akaike's Information Criterion coefficient c to determine fit of the data, 4 latent classes yielded better values resulting in four subgroups: 'asymptomatic,' 'upper' abdominal symptoms, 'lower' abdominal symptoms, and 'mixed' (upper and lower abdomen).

CONCLUSIONS

Latent class analysis identified 4 groups based on symptoms. This approach resulted in differentiation by anatomical region rather than the Rome IV classification of symptoms.

Symptom clusters in patients on dialysis and their association with quality-of-life outcomes

BACKGROUND

Patients who are on dialysis report multiple symptoms. The aim of the study was to explore and identify symptom clusters (co-occurring symptoms) in patients on dialysis and their possible associations with depressive symptoms and health-related quality-of-life (HRQOL) outcomes.

METHODS

In a cross-sectional study of 301 prevalent patients on dialysis, physical symptoms, depressive symptoms and HRQOL were assessed using the Beck Depression Inventory (BDI) and the Kidney Disease and Quality-of-Life-Short Form version 1.3 (KDQOL-SF36) questionnaires. Symptom clusters were identified using principal component analysis with varimax rotation. Multivariate linear regression analyses were carried out to evaluate the relationships between symptom clusters and depressive symptoms and HRQOL outcomes.

RESULTS

The majority of patients (63.5%) rated their symptoms in the 'very much' to 'extremely bothersome' range, and 29.4% had significant depressive symptoms. Three symptom clusters were identified and were named uraemic (nausea, lack of appetite, dizziness/faintness, feeling squeezed out, shortness of breath, chest pain), neuromuscular (numbness in extremities, sore muscles, cramps) and skin (itching, dry skin) clusters. The three clusters were associated with BDI, physical component summary (PCS) and mental component summary (MCS) scores. After multiple adjustments, the uraemic and neuromuscular clusters remained independently associated with BDI and PCS scores and the uraemic and skin clusters with MCS scores.

CONCLUSION

The strong associations between symptom clusters and depressive symptoms and the physical and mental domains of HRQOL should lead to an increased focus on symptom-alleviating interventions. Additional research is warranted to determine whether treatment of symptom clusters rather than single symptoms will improve HRQOL.

Do the digestive tract symptoms in eating disorder patients represent functional gastrointestinal disorders?

Background

Gastrointestinal (GI) symptoms are common in patients with eating disorders. The aim of this study was to determine, using factor analysis, whether these GI symptom factors (clusters) in eating disorder patients hold true to the Rome II classification of functional gastrointestinal disorders (FGIDs).

Methods

Inpatients in a specialised eating disorder unit completed the Rome II questionnaire. Data from 185 patients were analysed using factor analysis of 17 questions cited as present in 30% to 70% of the patients.

Results

Five factors emerged accounting for 68% of the variance and these were termed: ‘oesophageal discomfort’, ‘bowel dysfunction’, ‘abdominal discomfort’, ‘pelvic floor dysfunction’, and ‘self-induced vomiting’. These factors are significantly related to the Rome II FGID categories of functional oesophageal, bowel and anorectal disorders, and to the specific FGIDs of IBS, functional abdominal bloating, functional constipation and pelvic floor dyssynergia. Both heartburn and chest pain were included in the oesophageal discomfort factor. The ‘pelvic floor dysfunction’ factor was distinct from functional constipation.

Conclusions

The GI symptoms common in eating disorder patients very likely represent the same FGIDs that occur in non-ED patients. Symptoms of pelvic floor dysfunction in the absence of functional constipation, however, are prominent in eating disorder patients. Further investigation of the items comprising the ‘pelvic floor dysfunction’ factor in other patient populations may yield useful results.

Clustering and stability of functional lower gastrointestinal symptom after enteric infection

BACKGROUND

Current diagnostic criteria for functional gut disorder are based on symptom clusters observed after sporadic onset. It remains unclear whether symptoms group similarly in functional disorders of postinfectious etiology. We utilized observational data from the Walkerton Health Study (WHS) to: (i) determine groupings of functional gastrointestinal symptoms among patients exposed to acute gastroenteritis (GE), and (ii) assess the stability of these symptoms grouping over time.

METHODS

WHS participants 16 years of age and older at the time of the outbreak were included, if they had completed a modified Talley's Bowel Disease Questionnaire (BDQ) and responded 'yes' to a screening question as to whether they had experienced abdominal pain in the last 2 weeks. Exploratory factor analysis (EFA) using tetrachoric correlations was undertaken to identify symptom constructs. Hierarchical cluster analysis using the k-means method was used to create cluster groupings of patients based on these factors. Confirmatory factors analysis using responses to BDQ questionnaire administered at 4, 6, and 8 years after the outbreak was performed to assess stability of symptom domains over time.

KEY RESULTS

A total of 773 participants were eligible for inclusion [62.2% female, mean age 43.1 years (SD = 16.9)]. Eighty-four percent were exposed to acute GE during the outbreak. Two symptom groupings of abdominal pain with either diarrhea or constipation together explained 85.7% of the total variance. Cluster analysis identified four patients groupings based on these factors. These clusters could be qualitatively described as diarrhea- and constipation-predominant, mixed bowel pattern, and no predominance of bowel movements abnormalities. Results of the confirmatory factor analysis validating symptom domains identified in Year 1 showed that the baseline model was acceptable at 4 and 6 years after the outbreak and approached acceptability at 8 years. Values of root mean square error of approximation were 0.071 (90% CI: 0.053, 0.089) at 4 and 0.071 (90% CI: 0.049, 0.092) at 6 years and 0.089 (90% CI: 0.065, 0.114) at 8 years.

CONCLUSIONS & INFERENCES

The majority of subjects with postinfectious functional bowel disorders belong to groups with symptoms of abdominal pain and either diarrhea or constipation. These symptom groupings were stable across time.

Discriminant value of Rome III questionnaire in dyspeptic patients

BACKGROUND/AIM

Rome III criteria has modified the description of functional dyspepsia (FD) and divided this into subgroups. However, the discriminative value of Rome III questionnaire-based diagnosis of FD is yet to be determined.

OBJECTIVES

To evaluate the Rome III questionnaire for the diagnosis of FD and whether it can discriminate between postprandial distress syndrome (PDS) and epigastric pain syndrome (EPS) in patients with dyspeptic symptoms.

PATIENTS AND METHODS

Consecutive patients, who were not on proton pump inhibitors (PPI), were asked to participate. Patients who have previously established acid peptic disease or predominantly reflux symptoms or having alarm symptoms such as weight loss and hematemesis were excluded. Rome III questionnaire for FD was used to identify the patients as having FD and divide into its subgroups; PDS or EPS. Gastro-duodenal biopsies, liver function tests and ultrasound were done to establish the diagnosis of FD.

RESULTS

Out of 272 patients with upper gastrointestinal (GI) symptoms without alarm features, who were enrolled in the study, a total of 191 (70%) fulfilled the criteria of FD based upon Rome III questionnaire. EPS subgroup was found in 109 (57%), PDS in 17 (9%) patients, overlap between EPS and PDS was present in 56 (29%) patients. Nine (5%) patients remained indeterminate. Diagnosis of FD was established in 136/191 (71%) patients only. Gastritis was present in 116 patients (85%), Duodenitis in 44 (32%) and Helicobacter pylori infection in 70 (51%) patients. Among 55 patients (29%) who had organic diseases, EPS was seen in 35 (64%), PDS in 5 (9%) and overlap in 15 (27%) patients. Underlying organic causes were gastric or duodenal ulcers in 14 patients, Barrett esophagus in five, chronic liver disease in seven, gall stones in five, Giardiasis and celiac disease in three each. Gastric carcinoma, Crohns disease and gastric polyps were seen in one patient each.

CONCLUSION

This study indicates that 30% of patients who fulfilled the Rome III criteria for FD actually had organic disease. Almost one-third of patients with functional dyspepsia did not qualify for one of the two subgroups of FD of Rome III. There is also a need to further define the Rome III-based subgroups of FD for research purpose.

Symptom clusters: myth or reality?

Clinical experience suggests that many symptoms occur together. In this paper, we examine the rationale and evidence base for symptom clusters in different medical fields, particularly the cluster phenomenon in cancer. Cancer symptom clusters are a reality. Various symptoms that cluster clinically have also been verified statistically. Specific clusters such as nausea-vomiting, anxiety-depression, and cough-dyspnea are evident on both clinical observation and in research investigation. Fatigue-pain and fatigue-insomnia-pain have also been demonstrated statistically as clusters. Another proposed cluster 'depression-fatigue-pain' seems relevant to clinical practice. Other clusters may serve only as theoretical models that illustrate possible common biological etiologies in cancer; they need to be validated in future research. Analysis of the literature is complicated by considerable inconsistencies across studies. Discrepancies between clinically defined and statistically obtained clusters raise important questions. We must consider the analytical techniques used, and how methodology might influence cluster occurrence and composition. Further research is warranted to establish universally accepted statistical methods and assessment tools for symptom cluster research.

Validation of symptom-based diagnostic criteria for irritable bowel syndrome: a critical review

This article reviews the evidence for validity of symptom-based criteria (Manning, Rome I, Rome II, and Rome III) for irritable bowel syndrome (IBS). Two kinds of validations are reported: (i) studies testing whether symptom criteria discriminate patients with structural disease at colonoscopy from patients without structural disease; and (ii) studies testing whether symptom criteria discriminate patients presumed to have IBS by positive diagnosis from healthy subjects or patients with other functional and structural disorders. The first study type addresses an important clinical management question but cannot provide meaningful information on the sensitivity or positive predictive value because IBS is defined only by exclusion of structural disease. Specificity is modest (about 0.7) but can be improved to 0.9 by the addition of red flag signs and symptoms. The second type of study judges validity by whether the symptom criteria consistently perform as predicted by theory. Here, factor analysis confirms consistent clusters of symptoms corresponding to IBS; symptom-based criteria agree reasonably well (sensitivity, 0.4-0.9) with clinical diagnoses made by experienced clinicians; and patients with a clinical diagnosis of IBS who fulfill Rome II criteria have greater symptom severity and poorer quality of life than patients with a clinical diagnosis of IBS who do not fulfill Rome criteria. There are no consistent differences in sensitivity or specificity between Manning, Rome I, and Rome II. Both study types support the validity of symptom-based IBS criteria. Tests of Rome III are needed.

Differences in mortality in acute coronary syndrome symptom clusters

BACKGROUND

The timely and accurate identification of symptoms of acute coronary syndrome (ACS) is a challenge for patients and clinicians. It is unknown whether response times and clinical outcomes differ with specific symptoms. We sought to identify which ACS symptoms are related-symptom clusters-and to determine if sample characteristics, response times, and outcomes differ among symptom cluster groups.

METHODS

In a multisite randomized clinical trial, 3522 patients with known cardiovascular disease were followed up for 2 years. During follow-up, 331 (11%) had a confirmed ACS event. In this group, 8 presenting symptoms were analyzed using cluster analysis. Differences in symptom cluster group characteristics, delay times, and outcomes were examined.

RESULTS

The sample was predominantly male (67%), older (mean 67.8, S.D. 11.6 years), and white (90%). Four symptom clusters were identified: Classic ACS characterized by chest pain; Pain Symptoms (neck, throat, jaw, back, shoulder, arm pain); Stress Symptoms (shortness of breath, sweating, nausea, indigestion, dread, anxiety); and Diffuse Symptoms, with a low frequency of most symptoms. Those in the Diffuse Symptoms cluster tended to be older (P = .08) and the Pain Symptoms group was most likely to have a history of angina (P = .01). After adjusting for differences, the Diffuse Symptoms cluster demonstrated higher mortality at 2 years (17%) than the other 3 clusters (2%-5%, P < .001), although prehospital delay time did not differ significantly.

CONCLUSION

Most ACS symptoms occur in groups or clusters. Uncharacteristic symptom patterns may delay diagnosis and treatment by clinicians even when patients seek care rapidly. Knowledge of common symptom patterns may facilitate rapid identification of ACS.

Functional dyspepsia: not all roads seem to lead to rome

BACKGROUND

The Rome criteria have been introduced to create order in the heterogeneity of functional dyspepsia. The applicability of these symptom-based classification systems remains controversial.

GOAL

To evaluate the successive Rome criteria for functional dyspepsia in a large pool of patients with endoscopically verified functional dyspepsia.

STUDY

Patients referred to a secondary care district hospital were asked to fill out a questionnaire on gastrointestinal symptoms 2 weeks before upper gastrointestinal endoscopy. Patients were classified according to the Rome I, II, and III criteria for functional dyspepsia.

RESULTS

Nine hundred and twelve (70%) patients had no organic disorder explaining their symptoms. According to the Rome I, II, and III criteria, 371 (41%), 735 (81%), and 551 (60%) of these patients had functional dyspepsia, respectively. Twenty-five percent of patients had functional dyspepsia according to all 3 Rome criteria, whereas 15% was not classifiable at all. Forty-four percent and 42% of the patients, respectively, had epigastric pain syndrome and postprandial distress syndrome according to the Rome III criteria; however, 26% of all patients met both criteria and 40% was not classified at all.

CONCLUSIONS

The symptom-based Rome classification of functional dyspepsia does not lead to an easily applicable and consistent system that is useful in clinical practice or scientific research.

Current treatments in functional dyspepsia

By nature of the definition of functional dyspepsia (FD), organic causes have to be ruled out before therapy can be directed. However, in uninvestigated dyspepsia in the absence of alarm features, Helicobacter pylori "test and treat" or an empiric trial of acid suppression therapy for 4 to 8 weeks is reasonable. If alarm symptoms or signs are present, or if the dyspepsia symptoms first occur in those aged greater than 55 years, prompt esophagogastroduodenoscopy is mandatory to exclude serious disease and positively diagnose FD. Empiric acid suppression with H(2)-receptor antagonists or proton-pump inhibitors is superior to placebo in treatment of FD, but those patients with meal-related symptoms are least likely to respond. Helicobacter pylori eradication in FD benefits a minority of cases but is worthwhile, as response may be maintained. There is increasing evidence that some prokinetics may be superior to placebo in treatment of FD, but probably only a minority respond; those with meal-related symptoms may have the best response. Antidepressant therapy may have a place in management of difficult cases, but adequate randomized controlled trials are unavailable.

Functional defecation disorder as a clinical subgroup of chronic constipation: analysis of symptoms and physiological parameters

OBJECTIVE

Patients with functional constipation can be classified according to symptoms and physiological parameters as either having a disorder of defecation or having normal defecation. It is hypothesized that the disordered defecation, where it exists, is a causative factor of the constipation. However, the utility of this classification has yet to be proven in terms of predicting response to therapy. The definitions are non-specific and based on tests that are done in an artificial setting and with derived normal ranges. It is therefore possible that the symptoms and physiological parameters of a defecatory disorder may occur as a continuous spectrum in these patients, rather than defining a discrete entity or subtype. The aim of this study was to use cluster analysis and factor analysis of defecatory symptoms and physiological parameters to look for evidence of subgroups in patients with functional constipation.

MATERIAL AND METHODS

Consecutive patients presenting to a specialist constipation clinic and satisfying the inclusion criteria were assessed to determine the severity of defecatory symptoms, and underwent isotope defecating proctography and the Sitzmark transit study. Assessments were made contemporaneously and results of any test not performed within 6 weeks of the initial assessment were excluded. Principle components analysis and cluster analysis were performed to look for evidence of subgroups. Relationships between evacuatory symptoms, index parameters, and test results were explored. The detailed and unselected nature of the analyses produced hundreds of test results, and statistically significant results were critically evaluated in this context.

RESULTS

A total of 116 patients were studied (age range 18-73 years, mean 40.5 years). Based on the results of the transit study and proctography, 38% of patients showed evidence of slow transit constipation, 20% FDD (functional defecation disorder), 29% both, and 12% neither. Principle components analysis did not demonstrate an obvious dimension reduction for the variables tested. Cluster analysis (over 150 solutions tested) failed to show evidence of clustering. There were no useful predictive relationships between evacuatory symptoms, index parameters and test results.

CONCLUSIONS

We used multiple statistical analyses to look for clustering and predictive relationships between clinical and physiological parameters in consecutive patients with functional constipation and found no evidence of the existence of a subgroup of patients with a defecatory disorder. This may be due to weaknesses in the study design, poor validity of the assessments performed, or that defecatory features do not identify a distinct pathophysiological entity, but rather are manifested variably as a continuous spectrum.

Value of different diagnostic criteria for the irritable bowel syndrome among men and women

INTRODUCTION

Whether the diagnostic value of various criteria used to diagnose irritable bowel syndrome (IBS) differ by sex is controversial.

AIM

To evaluate the sex-specific value of varying IBS criteria and sex-specific symptoms in patients with IBS and organic disease.

METHODS

Outpatients of a gastroenterology practice (64% female) completed a validated questionnaire and received a complete diagnostic work-up as required. Questionnaire data were collected prospectively and audited retrospectively.

RESULTS

Overall 233 (male 21%) had a final diagnosis of IBS; 305 (male 47%) received a diagnosis of organic disease. Constipation and bloating were more frequent in females independent whether they had IBS or organic disease. The sensitivity of the diagnostic criteria in male patients was between 82% and 88%, when Manning (3 or more), Rome I or Rome II criteria were applied, whereas the specificity was 65% to 71%. In females, sensitivity was 62% to 64% and specificity was between 66% and 70%. Although all the diagnostic IBS criteria had higher positive predictive values in females versus males, the negative predictive values were lower in females.

CONCLUSIONS

Current criteria for IBS differ modestly between sexes, probably reflecting variable prevalence of the disease rather than a sex-specific presentation of IBS.

Cluster analysis of elderly cardiac patients' prehospital symptomatology

BACKGROUND

Chest pain routinely brings patients into the healthcare system, and elderly patients may present with more complex symptoms presaging ischemic heart changes than do younger patients.

OBJECTIVE

To examine, using cluster analysis, how elderly patients experiencing an ischemic coronary heart disease cluster based on presenting symptoms in the week before hospitalization and how they vary in terms of their general physical and mental health, mood states, and quality of life.

METHODS

Elderly (age >or=65 years), unpartnered patients (N = 247) admitted with ischemic coronary heart disease to one of five university medical centers were inducted into a clinical trial; only baseline data are reported. Interviews assessed cardiac symptoms, medical history, general physical and mental health, mood states, and quality of life. Patients were clustered (grouped) using squared Euclidean distances and weighted average linkage. Characteristics of patients were examined using analysis of variance and chi-squared analyses.

RESULTS

Three clusters (groups) were identified: (a) Classic Acute Coronary Syndrome (severe ischemic pain; 22%), (b) Weary (severe fatigue, sleep disturbance, and shortness of breath; 29%), and (c) Diffuse Symptoms (mild symptomatology; 49%). Post hoc tests revealed that the Weary group was more likely to have a history of heart failure; they also exhibited significantly more psychological distress and lower quality of life than the other subgroups.

CONCLUSION

Cluster analysis proved useful in grouping patients based on their symptom experience, but further research is needed to clarify the relationships among identified symptoms, psychological distress, and health outcomes; develop interventions for Weary patients; and extend the findings of this study.

Natural history of functional gastrointestinal disorders: a 12-year longitudinal population-based study

BACKGROUND & AIMS

Functional gastrointestinal disorders (FGID) are common in the community. The natural history of FGID is unknown because of a lack of prospective population-based studies and the indistinct nature of the phenotype. We sought to report the natural history of FGID in a US population.

METHODS

This prospective cohort study used data from multiple validated surveys of random samples of Olmsted County, MN, residents over a mean of a 12-year period between 1988 and 2003 (n = 1365). The surveys measured gastrointestinal symptoms experienced during the past year. Each subject received a minimum of 2 surveys. Point prevalence, onset, and disappearance rates and transition probabilities were calculated for individual FGIDs.

RESULTS

Between the initial and final surveys, the point prevalences (per 100 residents) were stable for irritable bowel syndrome (8.3% and 11.4%, respectively) and functional dyspepsia (1.9% and 3.3%, respectively). The onset of each of the disorders studied was greater than the disappearance rate, but the transition probabilities varied across the different subgroups. Among people with symptoms at baseline, approximately 20% had the same symptoms, 40% had no symptoms, and 40% had different symptoms at follow-up.

CONCLUSIONS

Although the prevalence of the FGID was stable over time, the turnover in symptom status was high. Many episodes of symptom disappearance were due to subjects changing symptoms rather than total symptom resolution. This transition between different FGIDs suggests a common etiopathogenesis.

Subtypes of functional dyspepsia

Functional dyspepsia is a common clinical condition characterised by chronic or recurrent upper abdominal pain or discomfort commonly associated with a variety of associated gastrointestinal symptoms and a normal endoscopy. To standardise research-based approaches, an initial categorisation of into sub groups was agreed to, based on clusters of symptoms. However the early expectation that these subgroups would be associated with distinct pathophysiologies amenable to specific therapy has not been realised. A classification based on the most troublesome symptom has been suggested but the utility of this is also unclear. More recent data suggest that some of the pathophysiologic dysfunctions may be associated with specific symptoms and so provide a better tool for grouping patients. But this approach remains incomplete as current insights into the pathogenesis are still too limited for this to be satisfactory. In conclusion, no classification provides for an adequate treatment-based approach to the syndrome of functional dyspepsia. As a consequence treatment remains largely empiric.

Symptom prevalence and clustering of symptoms in people living with chronic hepatitis C infection

Quality of life has been shown to be poor among people living with chronic hepatitis C. However, it is not clear how this relates to the presence of symptoms and their severity. The aim of this study was to describe the typology of a broad array of symptoms that were attributed to hepatitis C virus (HCV) infection. Phase 1 used qualitative methods to identify symptoms. In Phase 2, 188 treatment-naïve people living with HCV participated in a quantitative survey. The most prevalent symptom was physical tiredness (86%) followed by irritability (75%), depression (70%), mental tiredness (70%), and abdominal pain (68%). Temporal clustering of symptoms was reported in 62% of participants. Principal components analysis identified four symptom clusters: neuropsychiatric (mental tiredness, poor concentration, forgetfulness, depression, irritability, physical tiredness, and sleep problems); gastrointestinal (day sweats, nausea, food intolerance, night sweats, abdominal pain, poor appetite, and diarrhea); algesic (joint pain, muscle pain, and general body pain); and dysesthetic (noise sensitivity, light sensitivity, skin problems, and headaches). These data demonstrate that symptoms are prevalent in treatment-naïve people with HCV and support the hypothesis that symptom clustering occurs.

Validation of the pediatric Rome II criteria for functional gastrointestinal disorders using the questionnaire on pediatric gastrointestinal symptoms

OBJECTIVE

To validate the pediatric Rome II criteria for functional gastrointestinal disorders (FGIDs) using the Questionnaire on Pediatric Gastrointestinal Symptoms (QPGS).

METHODS

Subjects were 315 consecutive new patients, 4 to 18 years of age, seen in a tertiary care clinic and classified by pediatric gastroenterologists as having a functional problem. Patients and parents separately completed the QPGS before medical consultation. Diagnoses were derived using computer algorithms reflecting the Rome II criteria for pediatric FGIDs. Convergent validity was assessed by prevalence of diagnoses and internal validity using factor analysis to confirm symptom clusters of the criteria. Separate analyses were performed for 4 to 9 and 10 to 18 year olds, and for diagnoses based on parent and child reports.

RESULTS

In both age groups, the most prevalent diagnoses were irritable bowel syndrome (IBS) (22.0%, 35.5%), functional constipation (19.0%, 15.2%), and functional dyspepsia (FD) (13.6%, 10.1%). Parent-child concordance on diagnoses was generally poor. Factor analyses supported the internal validity of FD and of IBS symptoms except for relief with defecation. Although functional abdominal pain syndrome and abdominal migraine occurred rarely, symptom clustering within each diagnosis supports their validity. Among patients with abdominal pain, duration was of at least 3 months in most, and pain was of long duration and severe in at least one third.

CONCLUSION

More than half of patients classified as having a functional problem met at least one pediatric Rome II diagnosis for FGIDs. This study offers initial support for the validity of several of the criteria.

High and low unstimulated salivary cortisol levels correspond to different symptoms of functional gastrointestinal disorders

OBJECTIVE

It was examined whether unstimulated salivary cortisol levels as a psychobiological marker of stress reactivity correspond to psychological assessments of pain perception, depressive mood, and anxiety in patients with functional gastrointestinal disorder (FGD).

METHODS

A total of 30 patients was diagnosed according to the Rome diagnostic criteria for irritable bowel syndrome, nonulcer dyspepsia, or both conditions. Psychometric data were assessed by questionnaires, and salivary samples were collected for the measurement of cortisol levels after awakening and during the day. Patients were grouped by their awakening cortisol levels into low (G1), medium (G2), and high cortisol group (G3).

RESULTS

Psychiatric comorbidity did not differ between the groups. Analysis of variance (ANOVA) showed significant group differences with respect to pain perception and depressive mood, with the highest pain in G1 and the highest depression in G3.

CONCLUSION

The reported results are in line with prior research on hypothalamus-pituitary-adrenal (HPA) axis dysregulation in patients suffering from somatoform disorders on the one hand (low cortisol levels) and high cortisol levels in depression on the other. It is remarkable that our sample of patients of whom all received the same diagnosis, i.e., FGD, can be subdivided according to functional gastrointestinal symptoms, which correspond to the two types of cortisol alterations. The data provide evidence for psychobiological subgroups in FGD patients. As a consequence, the predominant symptoms reported by patients with FGD should carefully be taken into account to specify (psychotherapeutic) treatment.

Usefulness of chest pain character and location as diagnostic indicators of an acute coronary syndrome

This study assessed chest pain locations/symptoms among patients who presented with acute chest pain and how these compare with a clinical diagnosis of cardiac or noncardiac chest pain. A cluster analysis was undertaken to determine any pattern in the chest pain locations described by patients. Cluster analysis identified 4 distinct chest pain locations (upper chest, central retrosternal, central chest, and left chest and left arm). There was considerable location/symptom overlap between patients who had cardiac chest pain and those who had noncardiac chest pain.

Review article: the overlap between functional dyspepsia and irritable bowel syndrome -- a tale of one or two disorders?

Functional dyspepsia and irritable bowel syndrome are currently considered to be two separate nosological entities. However, the overlap of symptoms and the evidence of a number of common pathophysiological characteristics suggest that functional dyspepsia and irritable bowel syndrome may be different presentations of the same disorder. In this review, we critically appraise points in common, as well as differences, in the epidemiology, pathophysiology and response to treatment of functional dyspepsia and irritable bowel syndrome. Population-based studies and large case series show that one- to two-thirds of subjects with irritable bowel syndrome have symptoms that overlap with functional dyspepsia. Symptom analyses have generally failed to support functional dyspepsia and irritable bowel syndrome as separate entities. An exaggerated motor response to meals, delayed gastric emptying and abnormal small bowel and colonic transit can all be found in subsets of functional dyspepsia and irritable bowel syndrome, and are not exclusive to either condition. Visceral hypersensitivity is a common feature to both entities and seems unlikely to be site or disease specific. There is good evidence for the post-infectious development of irritable bowel syndrome, and this may also apply in functional dyspepsia. Psychiatric comorbidities are similar in functional dyspepsia and irritable bowel syndrome. Several common drug classes (prokinetics, visceral analgesics, psychoactive agents) may similarly improve both functional dyspepsia and irritable bowel syndrome symptoms. The evidence available suggests that at least subsets of functional dyspepsia and irritable bowel syndrome represent different manifestations of a single entity. The identification of common pathophysiological targets for therapy should be pursued in future research.

Management of Functional Abdominal Pain

The diagnosis of functional abdominal pain should be made based on the Rome II symptom criteria with only limited testing to exclude other disease. During physical examination the clinician may look for evidence of pain behavior which would be supportive of the diagnosis. Reassurance and proper education regarding the clinical entity of functional abdominal pain is critical for successful treatment and good patient satisfaction. Education should include validation that symptoms are real, and that other individuals experience similar symptoms. No further treatment may be required for those with mild symptoms. For patients with more severe symptoms, a long-term management plan of either pharmacological or psychological treatments is warranted. This will require a commitment by both the patient and the physician to engage in a partnership with active involvement and responsibility by both individuals. The goal of treatment--to decrease pain and increase function over time, not to cure the disorder-- should be explained. Strong consideration should be made for the use of an antidepressant to treat analgesic effects. Tricyclic antidepressants are the mainstay of therapy for functional pain disorders. The analgesic effect is generally quicker in onset and occurs at a lower dose than their effect on mood. To maximize patient compliance, patients should be told the rationale behind their use, warned of the potential side effects, and reassured that many of the side effects will disappear with time. Choice of an antidepressant should be based on the presence of concomitant symptoms (eg, depression), cost, and physician familiarity with specific agents. All patients with functional abdominal pain should be screened for underlying psychiatric disturbance as an untreated mood disorder will adversely affect response to treatment. If a concurrent mood disorder is found, it should be treated by either using a higher dose of the tricyclic antidepressant or by adding another antidepressant agent. Psychological interventions such as cognitive behavioral therapy may be important as adjuvant therapy or as an alternative to treatment with antidepressants for those patients who find antidepressants ineffective or are intolerant to them. Narcotics and benzodiazepines should not be used to treat chronic abdominal pain due to the high risk of physical and psychological dependence.