Abstract
Objective: To examine disparities between primary care provider (PCP) and gastroenterologist diagnosis and management of irritable bowel syndrome (IBS).
Design: Retrospective cross-sectional study.
Setting: A 547-bed quaternary-care hospital within the Loyola University Healthcare System.
Participants: 1000 patients aged 18-65 with an ICD-10 diagnosis of IBS
Methods: We randomly selected 1000 patients aged 18 to 65 years within the Loyola University Healthcare System’s electronic medical record with an ICD-10 diagnosis of IBS. Physician notes and diagnostic results were reviewed for documentation of symptoms fulfilling Rome IV criteria and resolution of symptoms. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of primary diagnoses assigned by PCPs and gastroenterologists were assessed along with number of diagnostic tests ordered.
Results: The mean age (SD) was 45 (12) years, and 76.9% were female. Sensitivity of an IBS diagnosis by a PCP was 77.6% (95% CI 73.3-81.9), compared with 60.1% (95% CI 54.7-65.6) for a gastroenterologist. Specificity of an IBS diagnosis by a PCP was 27.5% (95% CI 23.5-31.5), compared with 71.1% (95% CI 64.6-77.5) for a gastroenterologist diagnosis of IBS. A gastroenterologist diagnosis of IBS carried a high PPV (77.3%, 95% CI 72.0-82.6) compared with 44.6% (95% CI 40.7-48.5) for a PCP. Of 180 patients with outcome data, 69.4% had resolution of symptoms at follow-up.
Conclusion: The sensitivity of gastroenterologist diagnosis of IBS closely matches the sensitivity of Rome IV criteria in validation studies. The high specificity and PPV of gastroenterologists suggest more cautious diagnosis by gastroenterologists, with PCPs more likely to assign a diagnosis of IBS incorrectly or without sufficient documentation of symptoms fulfilling Rome IV criteria. Reported resolution rates suggest primary care management of IBS is appropriate, but PCPs may benefit from gastroenterologist consultation and diagnostic guidelines for greater specificity in diagnosing IBS.
Irritable bowel syndrome (IBS) is challenging from both a patient and provider standpoint. It is estimated that 10%–15% of the adult population in the United States suffers from IBS symptoms, yet only 5%–7% of adults have been diagnosed with the disease.1-4
When considering direct and indirect medical expenses, the cost burden of IBS is estimated to be tens of billions of dollars in the U.S. alone.5 Patients with IBS suffer a drastically reduced quality of life due to pain, impairment of function, or accompanying depression and anxiety.6-9
The current diagnostic standard is the Rome IV criteria, which mandate the presence of abdominal pain in addition to a change in bowel frequency and/or form, or relation of the pain to defecation. Symptoms must have been present at minimum an average of one day a week for the past 3 months, with symptom onset at least 6 months leading up to diagnosis.2,10,11
The criteria for diagnosing IBS have undergone a series of revisions designed to make them more applicable across cultures and practice settings, and therefore more relevant to both patients and providers.10,11 The IBS diagnosis is therefore based on the patient self-reporting symptoms, placing it among the functional gastrointestinal disorders (FGID). However, the FGID designation itself is under scrutiny, and a wealth of recent scientific evidence favors the new term “disorders of gut-brain interaction” (DGBI) to describe conditions such as IBS.7,10
Scientific understanding of IBS is rapidly evolving and underscores the complexity of the disorder. There are multiple subtypes within the diagnosis, and a patient may experience multiple subtypes over the course of the disease. Subtypes include constipation-predominant (IBS-C), diarrhea-predominant (IBS-D), mixed, (IBS-M) and unsubtyped.2,11 Post-infectious (PI-IBS) is specifically recognized as the presence of IBS symptoms (usually diarrhea-predominant) following an enteric infection.12,13 Most DGBI are understood under Rome criteria to be a spectrum of disease, with substantial overlap between conditions such as IBS-C and functional constipation,10,14,15 or IBS-D and small intestinal bacterial overgrowth (SIBO).16,17 It is clear that multiple factors may contribute to the condition.
Though IBS is sometimes conceptualized as a diagnosis of exclusion, multiple reviews have argued that the presence of the above symptoms with the absence of alarm symptoms amount to a positive diagnosis of IBS.18-20 Expert opinion concurs with this; a 2010 survey of 50 IBS experts found only 8% of them considered IBS a diagnosis of exclusion, compared with 72% of primary care providers (PCPs) and community gastroenterologists surveyed. Notably, providers who thought of IBS as a diagnosis of exclusion spent hundreds of dollars more in diagnostic testing.20 The recently published IBS guidelines from the American College of Gastroenterology (ACG) recommend that a positive paradigm of diagnosis and appropriate subtyping of the disease may improve both cost-effectiveness and time to initiation of therapy.20 However, due to the multi-factorial, evolving nature of IBS outlined above, and from the desire not to miss a more life-threatening diagnosis, PCPs can feel ill equipped to make a positive diagnosis of IBS. A recent survey of European general practitioners found 25% were uncomfortable assigning an IBS diagnosis without a gastroenterologist consultation.21 Yet specialist care itself has been tied to higher overall costs in IBS management.22 Therefore, there is a need to balance cost-effectiveness, timeliness, and expertise in the diagnosis and management of IBS. To identify barriers to accurately diagnosing IBS, we examined differences between PCP and gastroenterologist diagnosis and management of IBS to determine whether these two groups of clinicians differ significantly in diagnosing and managing IBS.
Methods
Over 3000 patient charts containing ICD-10 codes for IBS were obtained from the Loyola University Health System electronic medical records (EMR). We randomly selected 1000 charts of living patients between ages 18 to 65 years using a computer-generated list of random numbers and then reviewed physician encounter notes. Demographic, diagnostic, and symptom resolution data were collected where available, and Rome IV IBS criteria was retrospectively applied to each patient based on the clinical history documented in the chart. We reviewed notes for 12 months after the initial IBS diagnosis (not necessarily primary) for any encounter in which IBS was assigned as the primary diagnosis.
The IBS diagnosis was considered validated if Rome IV criteria was documented, either by the physician explicitly referring to Rome IV criteria or by comparing symptom descriptions and disease course across multiple encounters against Rome IV criteria. As the database search retrieved charts with any IBS diagnosis, we considered a diagnosis to be primary if it was the first diagnosis for the encounter, or if it was the first diagnosis related to the patient’s abdominal symptoms (e.g., in a PCP visit covering multiple systems). After primary diagnoses were established, we obtained rates of false positive (IBS diagnosed without fulfillment of Rome IV criteria) and false negative (other diagnosis assigned when Rome IV criteria were fulfilled) diagnoses among our two physician groups, as well as the most commonly occurring alternative primary diagnoses.
The number of diagnostic tests required to diagnose IBS was determined by separating patients who were exclusively diagnosed by PCPs from those exclusively diagnosed by gastroenterologists and comparing median number of diagnostic tests in a 12-month period before and after initial IBS diagnosis. IBS was only considered resolved if physician notes explicitly described amelioration of symptoms. Alternate primary diagnoses assigned to the encounter, including undifferentiated symptoms, were grouped into categories and the proportion of correct and incorrect diagnoses were compared within the physician groups. Protocols for this retrospective chart review were assessed by the Loyola University Health Sciences Institutional Review Board (IRB no. LU212541) and granted exemption status.
Statistical Analysis
Study data were collected and managed using research electronic data capture (REDCap) hosted at Loyola University Chicago.23,24 Contingency tables were constructed, and sensitivity, specificity, positive predictive value, and negative predictive value, were calculated for PCP and gastroenterologist diagnosis of IBS. To calculate confidence intervals (CIs), 95% exact binomial CIs were used. Comparisons between numbers of tests between PCP and gastroenterologist were evaluated using a Wilcoxon rank-sum test. Resolution of symptoms between groups was compared with Chi-square test. Paired data summaries and tests were used when there were multiple observations on the same individual (i.e,, when PCP and gastroenterologist had outcomes on the same patient, or when the ROME IV, PCP, and gastroenterologist diagnosis were paired on the same individual). Independent data summaries and tests were used when there were mutually exclusive groups (i.e, ‘PCP only’, gastroenterologist only’).All analyses were performed using SAS 9.4 (Cary, NC), and a two-sided p-value of <.05 was deemed statistically significant.
Results
The study population consisted of 1000 patients, aged 18-65 years. The mean age was 45 years with a standard deviation of 12 years; 76.9% were females. The most common IBS subtype was IBS-D, followed by IBS-C, and IBS-M. Together, these three subtypes accounted for 98.2% of all diagnoses (Table 1). PCPs saw 841 of the patients: 628/841 were diagnosed as IBS according to PCPs. However, only 280 patients were correctly diagnosed. Gastroenterologists saw 501 patients: 242/501 were diagnosed as IBS according to gastroenterologists. However, only 187 patients were correctly diagnosed. A total of 366 patients were seen by both PCP and gastroenterologists. There were 24 patients without documentary evidence of gastroenterologist and PCP diagnosis excluded from the analysis.
Patient characteristics
Analyzing all available data, the sensitivity of an IBS diagnosis by a PCP was 77.6% (73.3-81.9), compared with 60.1% (54.7-65.6) for a gastroenterologist. Specificity of an IBS diagnosis by a PCP was 27.5% (23.5-31.5), compared with 71.1% (64.6-77.5) for a gastroenterologist diagnosis of IBS. A gastroenterologist diagnosis of IBS carried a high positive predictive value (PPV) of 77.3% (72.0-82.6), compared with a PPV of 44.6% (40.7-48.5) for a PCP. When only paired data were used (N=366), sensitivity of PCP diagnosis was 67.6% (61.7-73.6), compared with 57.1% (50.9-63.4) for gastroenterologist diagnosis. Specificity of an IBS diagnosis by a PCP was 44.5%, (35.9-53.1) compared with 76.6% (69.2-83.9). A gastroenterologist diagnosis still carried a high PPV of 81.9% (76.1-87.8), compared with 69.4% (63.5-75.3) for a PCP diagnosis (Table 2). There was no significant difference between PCP (n = 392) and gastroenterologist (n = 75) regarding the median number of diagnostic tests required to manage IBS (3 vs. 2, P = 0.721) (Table 3). Of 174 patients with outcome data, 69.5% had resolution of symptoms at follow up. Of 58 patients seen by PCPs alone, 81.0% had resolution of symptoms, while 73.1% of 26 patients seen by gastroenterologists alone had resolution of symptoms. Only 61.1% of patients managed by both a gastroenterologist and a PCP reported resolution of symptoms, a finding that was statistically significant (P = 0.0335, Table 3). Gastroenterologists diagnosed bloating/eructation (57.7% under-diagnosis) and diarrhea/loose stools (70% under-diagnosis) rather than correctly diagnosing IBS at higher rates than they assigned a correct positive diagnosis. Gastroenterologists did not have any diagnosis categories in which a primary diagnosis of IBS was assigned rather than an alternate diagnosis (over-diagnosis) greater than the proportion of correct positive IBS diagnoses (Table 4). PCPs incorrectly diagnosed IBS (unsubtyped or other, 67.2% over-diagnosis) and IBS-C (56.8% over-diagnosis) at higher rates than they assigned a correct positive diagnosis. For PCPs, the only symptom for which the proportion of under-diagnosis was greater than the proportion of correct negative IBS diagnosis was diarrhea/loose stools (55.6% under-diagnosis, Table 5).
Sensitivity and Specificity of IBS diagnosis by PCP and GE
Resolution of symptoms of IBS
Correct diagnoses, alternative diagnoses or nonspecific symptom diagnoses ascribed to patients by GEs
Correct diagnoses, alternative diagnoses or nonspecific symptom diagnoses ascribed to patients by PCPs
Discussion
Consistent with prior studies, this study shows that IBS predominantly affects females, suggesting that our study population was adequately representative of the population of IBS patients. This study shows that sensitivity of gastroenterologist diagnosis of IBS was 60% (54.7-65.6). This matched closely with a previous study validating the Rome IV criteria, which found a sensitivity of 62.7% in a clinical sample.15 In that validation study, Palsson et al noted that substantial overlap between patients with IBS, functional diarrhea, and functional constipation decreases the sensitivity of the Rome IV criteria as a diagnostic tool.15 This is consistent with our observation that where gastroenterologists underdiagnose IBS, the most frequent non-specific symptom diagnoses were diarrhea, constipation, bloating, and abdominal pain.
Overall, gastroenterologists were overwhelmingly more specific (low rate of false positives) and also somewhat less sensitive in their diagnosis of IBS. We attribute this to the increased likelihood of gastroenterologists to have provided more precise descriptions of the patient’s condition (but may have ultimately decided to assign the primary diagnosis to a more pressing/acute condition). Between the two groups, PCPs had significantly lower specificity when compared with gastroenterologists (28% vs 70%). We attribute this to not only a lower rate of adequately documenting symptoms that could then be analyzed, but also to a lack of awareness among PCPs of when a DGBI qualifies as IBS, using an unsubtyped IBS diagnosis as a catch-all phrase to describe a functional disorder.
Taken together, the data in Tables 2 and 3 suggest that a gastroenterologist consultation in suspected IBS may be a useful way to increase the chances of a correct IBS diagnosis without incurring the costs of excessive diagnostic testing. The high sensitivity of PCP diagnosis is encouraging; however, the high false positive rate suggested by the low specificity could result in delayed diagnosis and treatment for other, more serious conditions. Though exact kinds of tests and their corresponding costs were not recorded, Table 3 shows that there was no significant difference in the number of diagnostic tests ordered by both physician groups, suggesting that consulting gastroenterologists is not likely to add additional costs to care of IBS patients. A gastroenterologist diagnosis, therefore, may be a useful diagnostic step following a positive IBS screen by a PCP.
The strengths of our study include the large sample size, use of simple random sampling to select the study population, application of the Rome IV criteria for diagnosis of IBS, and utilization of a 12-month window before and after IBS diagnosis to capture a primary IBS diagnosis, even if the physician had initially assigned a more symptoms-based diagnosis with the desire to monitor progression.
Limitations include the single-center retrospective design and reliance on physician documentation to determine whether a patient met criteria for IBS. Therefore, our conclusions on true and false positives and negatives should only be taken to indicate the level to which physicians adequately documented evidence for their IBS diagnosis, and is not intended to reflect actual prevalence of the disease. Moreover, prevalence of the IBS subtypes varies based on the edition of Rome criteria, and to date few studies on IBS prevalence have employed the most recent Rome IV criteria.
In a few cases, a PCP diagnosis of IBS would be based on a diagnosis by a gastroenterologist outside of our health system, and this gastroenterologist input was not reflected in our data collection tool. This may have contributed to both the higher sensitivity (PCP simply documenting a correct diagnosis from a specialist) and lower specificity (PCP may not have bothered to document fulfillment of criteria if primarily assigned by another physician) of the primary care group, though we expect that the number was not so large to significantly confound the data. Although, patients with an ICD-10 diagnosis of bile acid diarrhea (BAD) were excluded from the study population during the database search, the Selenium HomoCholic Acid Taurine (75SeHCAT) retention test to assess for BAD is not available in the United States, and measurements of total and individual fecal bile acids, collected over 48 hours, are not routinely performed as part of clinical care of patients with IBS-D. Therefore, the proportion of patients fulfilling the Rome IV criteria for IBS-D who actually have BAD could not be evaluated; this may have resulted in overestimation of the proportion of patients with IBS-D.25
Data on resolution of symptoms was limited to those cases where explicit documentation indicated that symptoms had resolved, but merit discussion nonetheless. IBS patients managed solely by a PCP appeared to experience good outcomes: 81% (47 of 58) patients seen by a PCP alone had resolution of symptoms, indicating that PCPs need not rely solely on a gastroenterologist for diagnosis and management. A slightly lower proportion of patients seen by a gastroenterologist alone (73.1%,19 of 26) had resolution of symptoms. A significantly lower proportion of patients managed by both a PCP and gastroenterologist reported resolution of symptoms (61.1% 55 of 90 patients, P=0.0335). This finding, may reflect a subset of more complex IBS cases in which PCPs and gastroenterologists are both involved. However, the resolution rate of 61.1% is significantly higher than reported resolution rates (37.5% to 47%) from systematic reviews of studies on interventions for IBS.26
PCPs and gastroenterologists were both likely to underdiagnose IBS when the patient presented with diarrhea/loose stools as the primary symptom, reflecting the subtlety in discerning between a presentation of loose stools and a true IBS diagnosis and the hindrances to properly documenting it, such as being aware of the symptom time course and properly addressing symptom frequency. These patients with a non-specific symptom diagnosis of diarrhea/loose stools may represent a subset of patients with an evolving diagnosis.
Our data, taken together with available research and recommendations, suggests that while PCPs may benefit from more information about IBS diagnosis, a single, early consultation with a gastroenterologist may improve efficiency of IBS diagnosis and management by increasing correct diagnosis rates while tending to decrease the number of tests ordered to arrive at the correct diagnosis. This study finds a robust resolution rate of IBS under PCP management, which is encouraging, as IBS can and should be managed on an outpatient basis, given that treatment is typically conservative. Investigation of an intervention to increase specificity of PCP diagnosis of IBS is warranted, but in the meantime consultation by a gastroenterologist shows promise in improving diagnostic accuracy without incurring additional costs.
- Received November 30, 2022.
- Revision received May 22, 2023.
- Accepted July 11, 2023.
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