The Prevalence, Comorbidity, Management and Costs of Irritable Bowel Syndrome: An Observational Study Using Routine Health Insurance Data
An observational study using routine health insurance data
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Background: Insufficient data are available on the administrative incidence and prevalence of irritable bowel syndrome (IBS) in Germany, as well as on its comorbidities, diagnostic evaluation, treatment, and costs.
Methods: We analyzed routine data from a statutory health insurance carrier with approximately eight million insurees. IBS was identified from the ICD-10 codes K58.0, K58.9, and F45.32 (outpatient care by a physician, outpatient and inpatient care in a hospital). The cumulative incidence for the year 2017 was determined by the exclusion of insurees who had carried the diagnosis of IBS in any of the preceding 12 years. The frequencies of comorbid diseases and of diagnostic and therapeutic measures were compared with those of persons in age- and sex-matched control groups without IBS.
Results: In 2017, the administrative incidence of IBS was 0.36%, and its prevalence was 1.34%. Persons with IBS were often documented as having other gastrointestinal diseases, headache, back pain, and mental disorders. There was evidence for the insufficient use of ultrasound and colonoscopy and for the excessive use of computed tomography and magnetic resonance imaging for diagnostic evaluation. The costs of medical care for insurees with IBS in the year of their initial diagnosis were higher than those of other insurees without the diagnosis of IBD (€ 3770 vs. € 2788) and rose in each of the eight years preceding the initial diagnosis.
Conclusion: Patients with IBS in Germany are likely not receiving sufficient diagnostic evaluation in conformity with the relevant guidelines. The high prevalence of comorbid mental disorders and other pain syndromes implies that the complaints of patients with IBS need to be more comprehensively evaluated and treated.
Irritable bowel syndrome (IBS) is a common and heterogeneous disorder in the general population (1). The individual burden on the patient due to the cardinal symptoms (abdominal pain, altered stool frequency and consistency), as well as the pathophysiological mechanisms (e.g., visceral and central nervous hypersensitivity, altered gastrointestinal motility, immunity, and microbiota), differ from patient to patient (2) (Box).
IBS is considered a functional disorder (3). Functional disorders that have no specific biomarkers are often underdiagnosed in the primary care setting (4). In fibromyalgia syndrome, for example, there is a marked discrepancy between its administrative prevalence (prevalence of the diagnosis among health insurances) (5) and potential cases in epidemiological studies (6). There is recent data from Germany on the prevalence of potential IBS cases in the general population (7, 8), not, however, on its administrative prevalence.
The biopsychosocial model postulates that IBS is the final common pathway of a number of interacting somatic and psychosocial pathogenetic processes (9). There are reports on associations in the general population between IBS and gastrointestinal infections (approximately 10%) (2, 10), other functional disorders with pain as the cardinal symptom (e.g., tension headache, fibromyalgia syndrome) (20%–65%), and a lifetime prevalence (varying according to medical treatment) of 5%–70% for depressive disorders and anxiety disorders (11). To our knowledge, the administrative prevalence of these comorbidities has not been investigated as yet.
The diagnosis is made based on a patient history involving a typical complex of symptoms and the exclusion of other disorders that could likely be responsible for these symptoms (2). General and individual laboratory and stool tests, abdominal ultrasound, one-off ileoscopy, and, in females, a gynecological examination are recommended as part of the basic diagnostic workup. Depending on patient history and symptom constellation, a tailored and stepwise further diagnostic approach is recommended. Overdiagnosis and the undifferentiated use of resources should be avoided. In the case of a typical patient history and the absence of warning signs, one can establish the suspected diagnosis without ileoscopy. Therapy is based on general treatment principles, dietetic recommendations, psychotherapeutic methods, as well as symptomatic drug treatment (2). As far as we are aware, there are no data on the extent to which guideline-compliant diagnosis and treatment are carried out for IBS in Germany.
In other countries, IBS is associated with relevant direct healthcare costs, e.g., € 567 to € 862 per year/patient in France (12). Only data from general medical practices without control groups for 2002 are available on IBS patients for Germany (13).
Due to this lack of data in Germany on these topics, the following questions will be investigated on the basis of routine data from the German Barmer health insurance:
- How high are the administrative incidence and prevalence of IBS?
- Which comorbidities (gastrointestinal disorders, infections, other functional disorders, mental disorders) are associated with IBS?
- Which diagnostic measures and treatments are performed prior to the diagnosis of IBS?
- How high are the costs of medical treatment once IBS has been diagnosed?
There were no pre-defined hypotheses.
Data analysis and presentation were carried out according to the German Strosa 2 (STandardisierte BerichtsROutine für SekundärdatenAnalysen) reporting standard for secondary data analyses (14). These are based on pseudonymized and longitudinal Barmer data that are linkable in a cross-sectoral manner for the years 2005–2017, with more than 8 million individuals nationwide being insured with the Barmer in any one of these years. The codes K58.0 (irritable bowel syndrome with diarrhea), K58.9 (irritable bowel syndrome without diarrhea or without further details), and F45.32 (somatoform autonomic dysfunction of the lower gastrointestinal tract) according to the international statistical classification of diseases (ICD-10) were deemed an indication of IBS. Diagnostic information on outpatient medical treatment as well as diagnoses from outpatient and inpatient treatment in hospitals were taken into account. Diagnosis documentation in the outpatient setting was only taken into account if the diagnosis was classified as “confirmed.”
Administrative 1-year prevalences and incidences (cumulative) were determined for 2017. The incidence was determined after all insured individuals diagnosed with IBS in the 12 preceding years (2005–2016) were excluded, whereby documented insurance with the Barmer in all quarters of the specified years except for the year of birth was a prerequisite. To obtain representative estimators of prevalences and incidences, these individuals were standardized into corresponding groups for 2017 based directly on sex, 1-year age groups, and federal state of residence according to information from the Federal Statistical Office of Germany on the average German population. In comparisons of annual expenditure for IBS patients and non-IBS patients, results on non-IBS patients were standardized directly according to sex and age structure of IBS patients. For analyses involving time differentiation into quarterly periods, affected patients (cases) were matched with non-affected individuals (controls) of corresponding sex, age, and federal state. When analyzing comorbidities, observed diagnosis rates (i.e., the percentage of individuals with a particular diagnosis) for IBS-affected individuals in 2017 were compared with diagnosis rates that would have been expected for the sex and age structure of IBS patients according to data on non–IBS-affected individuals. This approach equates to indirect standardization and yields quotients of observed and expected percentages of affected subjects. A value of 2.0 indicates that, in IBS cases, a diagnosis or service was documented twice as often as expected. A value of 0.5 indicates that a diagnosis/service was coded only half as often in IBS cases compared to controls. For the quotients, 99% confidence intervals are reported (15).
The costs of outpatient and inpatient treatment as well as drug prescriptions were determined for affected individuals, not only for the year of initial diagnosis (2017) but also for the 8 years prior to initial diagnosis, and compared with costs for non-affected individuals. The eMethods section provides details on the methodology used to determine comorbidities, drug prescriptions, and medical services.
Coding by specialist groups
In all, 73.9% of IBS subjects were given the ICD-10 code K58.9, while the code K58.0 was documented in 24.3% and the code F45.32 in 7.3% of cases. The IBS diagnosis (K58.0, K58.9, F45.32) was also documented in physicians’ billing data for 98.7% of affected individuals; an IBS diagnosis was the main discharge diagnosis for 0.7% and thus the main reason for inpatient treatment in hospital.
A total of 83.4% of affected individuals with an IBS diagnosis in the billing data of statutory health insurance physicians received their diagnosis from their general practitioner. The diagnosis was documented by gastroenterologists in 6.6% of cases and by gynecologists in 3.2%. The code F45.32 was documented by general practitioners in 64% of affected individuals, by medical psychotherapists/psychiatrists and psychological psychotherapists in approximately 9%, and by pediatricians in 11%.
Within the year 2017, 1.34% of the population was diagnosed with IBS according to results standardized for sex, age, and location of residence. This corresponds to around 1.1 million affected individuals in Germany. At a percentage of 1.78%, females were affected roughly twice as frequently as were men at 0.89%.
Before the age of 14 years, the administrative prevalences for both sexes were under 0.3%. A first frequency peak was seen in 2017 in women aged 25 years. The highest administrative prevalences were seen at the age of approximately 75–80 years (eFigure).
There were regional differences in administrative prevalences that cannot be explained by the differing average incomes in the various districts (data available on request).
Initial diagnoses: incidence
In 2017, an initial IBS diagnosis was documented in 0.36% of the population that had not been affected in the preceding 12 years (males: 0.27%; females: 0.46%). According to these results, one can expect around 285 000 initially diagnosed cases of IBS per year. Individuals aged between 20 and 25 years were most frequently affected, with the rate of new cases or initial diagnoses totaling 0.9% in females of this age and 0.4% in males (eFigure).
Diagnoses differentiated according to ICD-10 chapters were more common in IBS-affected individuals in 20 of altogether 22 disease types compared to individuals without an IBS diagnosis (with the exception of Chapter XV “Pregnancy, childbirth and the puerperium” and XVI “Certain conditions originating in the perinatal period”; [Table 1]).
Of insured individuals with an IBS diagnosis, 45% had other “diseases of esophagus, stomach and duodenum” documented, 38% had “symptoms and signs involving the digestive system and abdomen” documented, 15% “intestinal infectious diseases,” 13% “noninfective gastroenteritis and colitis,” 8% “lactose intolerance,” and 5% “candidiasis” (eTable 1).
In addition, 70% of insured individuals with an IBS diagnosis had “dorsopathies” documented, 58% had “neurotic, stress-related and somatoform disorders” documented, 42% had “affective disorders” documented (primarily depression); 25% “headache,” and 20% “pain, not elsewhere classified” (eTable 2).
At least one ultrasound of the abdominal or pelvic region was performed in 62% of RDS patients on an outpatient basis in the four quarters leading up to and including the quarter of initial diagnosis. 53% of females were examined by a gynecologist. Colonoscopy was performed in 30% and esophagogastroduodenoscopy in 26%, while, in terms of imaging techniques, computed tomography (CT) was used in 7.0% and magnetic resonance imaging (MRI) of the abdominal and pelvic region in 3.2% (combined outpatient and inpatient figures) (Table 2).
In 2017, 40% of insured individuals diagnosed with IBS were prescribed proton pump inhibitors, 26% antidepressants, and 25% “other analgesics and antipyretics” (Table 3).
In the four quarters leading up to as well as in the quarter of the diagnosis, services falling under guideline psychotherapy were used in 58% of IBS cases. Altogether 26% underwent specialist psychiatric or psychosomatic treatment in an outpatient setting, while 4% underwent inpatient psychotherapy (eTable 3).
Costs of medical care
Annual expenditure increased over the observation period 2009–2017 in both groups. For all years, the average costs of IBS cases were higher than in the control group. Between 2009 and 2016, a steady increase in these differences from € 277 to € 462 was observed. IBS cases first diagnosed in 2017 generated costs of € 3770, which exceeded the average costs for controls by € 982 (Figure). The difference compared to controls was primarily due to the higher costs for outpatient (2017: € 445) and inpatient (2017: € 483) treatment.
The administrative prevalence of IBS in Germany is considerably lower than the prevalence of potential IBS cases in epidemiological studies. The prevalence of IBS according to the Rome-III criteria was 16.6% in a Germany-wide sample of 14- to 80-year-olds in the years 2011–2012 (7) and 3.5% in the years 2008–2012 in the German federal state of Mecklenburg–West Pomerania (8). The administrative prevalence in < 14-year-olds (approximately 0.2%) according to Barmer insurance data also differs from the prevalence of potential cases in 6- to 10-year-old school children in Germany (4.9%) (16). Routine data from the Bavarian Association of Statutory Health Insurance Physicians for 2013 also showed a low administrative prevalence for IBS (K58.0 and K58.9) of 1.0% and an incidence of 0.4% (17).
This discrepancy can be explained by the following findings:
- Only 50%–60% of potential IBS cases in epidemiological studies sought medical treatment (7, 18).
- The attitudes and behavior not only of affected patients (e.g., complex and inconsistent description of symptoms; insistence that symptoms have a somatic cause) but also of physicians (e.g., fixation on biomedical parameters; rejection of diagnoses without biomarkers) hamper the diagnosis of functional disorders (4).
- German physicians use other and stricter diagnostic criteria than the Rome-III criteria (abdominal pain or abdominal discomfort associated with altered stool frequency and consistency on at least 3 days/month in the previous 3 months) (19), for instance the German clinical practice guideline on IBS (2) (Box).
The higher proportion of female patients (two-fold) in the present sample correlates with the results of the two recent German epidemiological samples (1.7-fold) (7, 8). As in the study conducted by Althaus (7), the age distribution peaked in early adulthood.
The high rate of comorbid mental disorders, in particular anxiety and depressive disorders (10), known from population and clinical samples, was also evident in the administrative prevalence seen in the analyzed Barmer insurance data. In addition to gastrointestinal infections, anxiety and stress have been confirmed in prospective studies as risk factors for IBS (19, 20). The same findings apply to the association with other structural disorders (e.g., chronic inflammatory bowel disease) (21), other functional disorders of the gastrointestinal tract (“unhappy gut”) (22), and other chronic pain syndromes. In the US, the association between functional pain syndromes (IBS, chronic headache, back and lower abdominal pain, temporomandibular disorders) falls under the umbrella term “chronic overlapping pain conditions” (23).
Up to 50% of IBS patients in the general population as well as in clinical studies report food intolerances (2). The administrative prevalence of food intolerances is significantly lower in the present sample.
The following are possible explanations:
- There are no ICD-10 codes for a number of food intolerances such as histamine intolerance and non-celiac wheat sensitivity.
- Practitioners did not perform tests for food intolerances or did not code these.
- If a food intolerance was detected, no IBS was coded.
The link to the diagnosis of mycosis (and the prescription of antifungal agents) suggests possible misdiagnosis and incorrect treatment. The German IBS guidelines do not recommend “stool ecograms,” i.e., quantitative stool flora analysis (percentage of individual bacteria and fungi in stool) (2). According the authors’ clinical experience, these are carried out in clinical practice at the cost of the patient. If Candida albicans is detected, non-indicated antifungal treatment is performed.
In the year prior to initial diagnosis, almost a third of IBS patients underwent the colonoscopy recommended in the German clinical practice guideline on IBS (2) and around two thirds abdominal ultrasound. We suspect that physicians dispensed with colonoscopy in the case of young patients without somatic red flags and in those with normal fecal calprotectin. However, when applying the recommendations of the German IBS guidelines—which require the exclusion of an inflammatory bowel disease by colonoscopy for a definitive diagnosis of IBS—too few colonoscopies have been performed. The British guidelines issued by the National Institute for Health and Care Excellence, on the other hand, do not recommend colonoscopy in adults if the patient history meets IBS criteria (24). Although the German clinical practice guideline on IBS recommends further diagnostic tests to exclude other disorders in the case of clinical signs of a structural disorder, the frequency with which CT and MRI are performed, particularly in the inpatient setting, points to possible overdiagnosis.
It is not possible to determine from billing data whether drug prescriptions were for IBS or for other disorders. The high number of opioid prescriptions is cause for concern. The German IBS guidelines do not recommend opioids (2), which may even exacerbate IBS symptoms such as abdominal pain and constipation (narcotic bowel syndrome) (25).
The higher medical costs for IBS cases during the entire study period compared to controls illustrate the significance of illness behavior. The intensity of symptoms as well as psychological factors such as disease anxiety and perceived stress have been shown to be determinants in the use of health services for gastrointestinal symptoms (1).
The following limitations of this study need to be taken into consideration:
- The analyzed data were collected for billing purposes. The reliability of the diagnoses has not been verified.
- The fact that evaluations were restricted to individuals insured with one single statutory health insurance and did not take privately insured individuals into account may limit the representativeness of the findings.
- It was not possible to comprehensively determine treatment costs, since some drugs used in IBS, such as laxatives, probiotics, and digestives, are obtainable over-the-counter. Furthermore, the use of alternative treatments that do not fall within the range of services offered by the statutory health insurances was not taken into account.
Routine Barmer data demonstrate the relevance of IBS in Germany in terms of health economics. The high prevalence of comorbid mental disorders and other pain syndromes points to the need for a comprehensive evaluation of patients’ symptoms and the deployment of general treatment principles for functional disorders, such as aerobic training and centrally active therapies (psychotherapy, antidepressants as pain modulators) (26).
Conflict of interest statement
Prof. Layer received honoraria for consultancy from Allergan.
Prof. Häuser receives royalties for a CD containing medical hypnosis for IBS patients from Hypnos Verlag.
Dr. Grobe worked on numerous projects financed by various statutory health insurances.
The remaining authors state that they have no conflicts of interest.
Manuscript submitted on 20 March 2019, revised version accepted on 14 May 2019.
Translated from the original German by Christine Rye.
Prof. Dr. med. Winfried Häuser
Klinik für Innere Medizin I
66119 Saarbrücken, Germany
Cite this as:
Häuser W, Marschall U, Layer P, Grobe T: The prevalence, comorbidity, management and costs of irritable bowel syndrome—an observational study using routine health insurance data. Dtsch Arztebl Int 2019; 116: 463–70. DOI: 10.3238/arztebl.2019.0463
Kompetenzzentrum Medizin/Versorgungsforschung, BARMER, Wuppertal: Dr. med. Ursula Marschall
Israelitisches Krankenhaus, Hamburg: Prof. Dr. med. Peter Layer
Institute for Applied Quality Improvement and Research in Health Care, Göttingen: Dr. med. Thomas Grobe
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