From the Guidelines
Irritable Bowel Syndrome (IBS) is primarily a diagnosis of exclusion, though this approach has evolved somewhat with the development of symptom-based criteria, as highlighted in the most recent study from 2023 1. When diagnosing IBS, clinicians typically first rule out other conditions that could explain the patient's symptoms, such as inflammatory bowel disease, celiac disease, microscopic colitis, or colorectal cancer. This exclusionary process usually involves laboratory tests including complete blood count, C-reactive protein, celiac serology, and often a colonoscopy depending on the patient's age and risk factors. Once these conditions are ruled out, physicians then apply the Rome criteria, which include recurrent abdominal pain associated with defecation changes and altered stool frequency or form, as noted in the study from 2023 1. While these positive diagnostic criteria help standardize the diagnosis, the exclusion of other potential causes remains a fundamental part of diagnosing IBS. This approach is necessary because IBS symptoms overlap with many other gastrointestinal disorders, and there is currently no definitive biomarker or test that can independently confirm an IBS diagnosis, a point also made in a previous guideline from 2021 1. However, the most recent and highest quality evidence from 2023 1 emphasizes the importance of limited testing to exclude common organic disorders that can mimic IBS, rather than exhaustive investigation. Key points to consider in the diagnosis of IBS include:
- Careful history taking to identify cardinal symptoms of IBS
- Limited testing to exclude organic disorders such as coeliac disease
- Application of the Rome criteria for symptom-based diagnosis
- Consideration of mental health comorbidity and the potential need for multidisciplinary management, as discussed in the 2023 study 1.
From the Research
Definition of IBS as a Diagnosis of Exclusion
- IBS is widely considered a diagnosis of exclusion, despite evidence contradicting this approach 2.
- However, some studies suggest that IBS can be identified by symptom-based criteria, making it a diagnosis that can be identified positively 3, 4.
Symptom-Based Criteria for IBS
- Symptom-based criteria, such as the Rome criteria, can be used to make a positive diagnosis of IBS 3, 5, 4.
- These criteria include abdominal pain associated with abnormal stool consistency and/or frequency, and the absence of alarm signs or symptoms 2, 3.
Clinical Practice and Diagnosis of IBS
- Despite guidelines recommending a positive diagnosis of IBS using symptom-based criteria, many clinicians believe that IBS is a diagnosis of exclusion and order unnecessary tests 6.
- Experts in the field are more likely to make a positive diagnosis of IBS and order fewer tests, resulting in lower costs and more efficient care 6.
- The use of adjunctive diagnostic tools, such as stool-form examination and serum biomarkers, may aid in the diagnosis of IBS and increase physician confidence 4.