What are the diagnostic criteria for Irritable Bowel Syndrome (IBS)?

From the Guidelines

Irritable bowel syndrome (IBS) is diagnosed using the Rome IV criteria, which requires recurrent abdominal pain at least one day per week in the last three months, with symptom onset at least six months prior to diagnosis, as outlined in the British Society of Gastroenterology guidelines 1. The diagnosis of IBS is based on a positive approach, using symptom-based diagnostic criteria, with limited investigations to rule out other conditions.

Key Diagnostic Criteria

• Recurrent abdominal pain, on average, at least 1 day per week in the last 3 months
• Associated with two or more of the following:
  • Related to defaecation
  • Associated with a change in frequency of stool
  • Associated with a change in stool form

Classification of IBS

Patients may be classified into subtypes based on predominant stool patterns:

• IBS with predominant constipation (IBS-C)
• IBS with predominant diarrhea (IBS-D)
• IBS with mixed bowel habits (IBS-M)
• IBS unclassified (IBS-U), as described in the guidelines 1. The diagnosis relies heavily on symptom-based criteria because there is no specific biomarker or test that definitively confirms IBS, which is fundamentally a disorder of gut-brain interaction involving visceral hypersensitivity and altered gut motility.

Diagnostic Approach

Doctors typically perform basic blood tests, stool tests, and sometimes colonoscopy to rule out other conditions like inflammatory bowel disease, celiac disease, or microscopic colitis, as part of a comprehensive diagnostic approach 1.

From the FDA Drug Label

The Rome II criteria further categorizes IBS patients into 3 subtypes: diarrhea-predominant IBS (IBS-D), constipation-predominant IBS (IBS-C), or alternating IBS (bowel habits alternating between diarrhea and constipation). *Rome II Criteria: At least 12 weeks, which need not be consecutive, in the preceding 12 months of abdominal discomfort or pain that has two out of three features:

1. Relieved with defecation; and/or
2. Onset associated with a change in frequency of stool; and/or
3. Onset associated with a change in form (appearance) of stool Symptoms that Cumulatively Support the Diagnosis of Irritable Bowel Syndrome: – Abnormal stool frequency (for research purposes “abnormal” may be defined as greater than 3 bowel movements per day and less than 3 bowel movements per week); Abnormal stool form (lumpy/hard or loose/watery stool); Abnormal stool passage (straining, urgency, or feeling of incomplete evacuation); Passage of mucus; Bloating or feeling of abdominal distension. **Rome III Criteria: Recurrent abdominal pain or discomfort (uncomfortable sensation not described as pain) at least 3 days/month in last 3 months associated with two or more of the following:
4. Improvement with defecation;
5. Onset associated with a change in frequency of stool;
6. Onset associated with a change in form (appearance) of stool

The diagnostic criteria for Irritable Bowel Syndrome (IBS) are defined by the Rome II and Rome III criteria, which include:

• Abdominal discomfort or pain with at least two of the following features:
  • Relieved with defecation
  • Onset associated with a change in frequency of stool
  • Onset associated with a change in form (appearance) of stool
• Symptoms that cumulatively support the diagnosis:
  • Abnormal stool frequency
  • Abnormal stool form
  • Abnormal stool passage
  • Passage of mucus
  • Bloating or feeling of abdominal distension
• Rome III criteria specify recurrent abdominal pain or discomfort at least 3 days/month in the last 3 months, associated with two or more of the following:
  • Improvement with defecation
  • Onset associated with a change in frequency of stool
  • Onset associated with a change in form (appearance) of stool 2

From the Research

Diagnostic Criteria for Irritable Bowel Syndrome (IBS)

The diagnosis of IBS is based on characteristic symptoms, as outlined in several symptom-based criteria, including:

• Manning criteria 3
• Rome criteria (I, II, III, and IV) 3, 4, 5, 6
• Kruis score 4

Symptom-Based Diagnostic Criteria

These criteria are used in combination with a detailed history, physical examination, and limited diagnostic testing to diagnose IBS 7, 3. The Rome criteria, in particular, are widely used and have been updated over time to improve diagnostic accuracy 6.

Laboratory Investigations

Laboratory tests, such as complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), may be used to exclude other medical conditions with similar presentations 4.

Clinical Examination

A clinical examination and physical examination should be supplemented with laboratory indicators to increase the likelihood of identifying IBS 4.

Key Symptoms

The key symptoms of IBS include:

• Abdominal pain
• Bloating
• Disturbed defecation
• Changes in bowel habits (constipation or diarrhea) 7, 3, 5, 6