Rome III in Diagnosing Post-Infectious Irritable Bowel Syndrome: Roma IV Makes a Few Modifications

The Rome III criteria play a critical role in diagnosing post-infectious irritable bowel syndrome (PI-IBS), a subtype of irritable bowel syndrome (IBS) that develops after an acute gastrointestinal infection, such as gastroenteritis. These criteria, established by a group of experts, provide a standardized framework for diagnosing IBS based on symptom patterns, which helps ensure consistency and accuracy across clinical settings.

Here’s how the Rome III criteria are relevant to diagnosing PI-IBS:

1. Symptom-Based Diagnosis: According to Rome III, IBS is diagnosed based on the presence of recurrent abdominal pain or discomfort for at least 3 days per month in the past 3 months, along with two or more of the following:
   • Improvement with defecation,
   • Onset associated with a change in stool frequency,
   • Onset associated with a change in stool form (appearance).
   For PI-IBS, these symptoms must occur after an acute infectious episode, typically following gastroenteritis or food poisoning, which distinguishes it from other forms of IBS.
2. Exclusion of Other Causes: The Rome III criteria emphasize the need to rule out other organic causes of gastrointestinal symptoms through clinical assessment and tests. For PI-IBS, this is particularly important as symptoms can resemble other post-infectious conditions, such as inflammatory bowel disease or ongoing infections.
3. Chronicity of Symptoms: Symptoms must persist for at least 6 months before a diagnosis of IBS can be made, according to the Rome III guidelines. For PI-IBS, the diagnosis is usually considered when symptoms persist beyond the resolution of the initial infection, typically for several months or longer.
4. Distinguishing Features: PI-IBS often presents with specific characteristics, such as the sudden onset of symptoms after an infection, diarrhea as a predominant symptom, and a history of an acute bacterial, viral, or parasitic gastroenteritis. The Rome III criteria help clinicians recognize these features and differentiate PI-IBS from other functional GI disorders.

Although the Rome III criteria were replaced by the Rome IV criteria in 2016, they were influential in guiding the diagnosis of IBS and its subtypes, including PI-IBS, during their use. The newer Rome IV criteria have updated the definitions and symptom thresholds, but the role of symptom-based diagnosis remains central in PI-IBS.

What changes were made with the Rome IV criteria in 2016?

The Rome IV criteria, introduced in 2016, updated the diagnostic guidelines for functional gastrointestinal disorders, including irritable bowel syndrome (IBS), building upon the Rome III criteria. Several important changes were made to refine the diagnosis of IBS and better reflect the evolving understanding of the condition.

Here are the key updates made with the Rome IV criteria:

1. Refinement of Diagnostic Thresholds

• Rome III defined IBS based on recurrent abdominal pain or discomfort. The term “discomfort” was removed in Rome IV, and only “pain” is now considered a diagnostic criterion. This change reflects the understanding that “discomfort” is too vague and may not be as helpful in identifying IBS.
• Abdominal pain must now occur at least one day per week on average over the previous 3 months, rather than the Rome III requirement of 3 days per month, making the criteria stricter and ensuring that only patients with more frequent symptoms are diagnosed.

2. Emphasis on Pain as a Core Symptom

• The Rome IV criteria highlight abdominal pain as the central feature of IBS, while changes in bowel habits (such as stool frequency and form) are secondary features. This contrasts with Rome III, where both pain and discomfort were emphasized equally.

3. Changes in Subtypes of IBS

• The classification of IBS subtypes remains similar, but there is a greater emphasis on the variability of symptoms over time. The subtypes (IBS-D for diarrhea-predominant, IBS-C for constipation-predominant, IBS-M for mixed, and IBS-U for unsubtyped) were retained, but clinicians are encouraged to consider that symptoms may change over time, and patients may not always fit neatly into one category.

4. Post-Infectious IBS (PI-IBS)

• PI-IBS is more explicitly recognized in the Rome IV criteria, acknowledging the role of a preceding infectious event. This includes a clearer understanding of how an acute gastrointestinal infection, particularly gastroenteritis, can lead to persistent IBS symptoms.

5. Increased Focus on the Brain-Gut Axis

• The Rome IV criteria emphasize the role of the brain-gut interaction more clearly, recognizing IBS as a disorder of gut-brain interaction rather than solely a gastrointestinal disorder. This shift reflects the growing awareness of the psychological and emotional components of IBS, including the impact of stress, anxiety, and depression on symptom severity.

6. Greater Recognition of Extra-Gastrointestinal Symptoms

• The Rome IV criteria acknowledge that patients with IBS often experience symptoms beyond the gastrointestinal tract, such as fatigue, headache, and muscle pain. While these symptoms do not directly contribute to the diagnosis of IBS, their inclusion highlights the broader impact of the disorder on patients’ overall health and well-being.

7. Removal of the Term “Functional”

• Rome IV removes the term “functional” in favor of describing these disorders as disorders of gut-brain interaction. This change helps destigmatize the conditions by moving away from the implication that the symptoms are only due to abnormal function without a structural or biochemical cause.

8. Improved Clarity and Language

• The Rome IV criteria use clearer and more precise language to avoid ambiguity and ensure that patients are diagnosed accurately. For instance, “discomfort” was seen as too broad and subjective in the Rome III criteria, and its removal helps sharpen the focus on pain as a measurable and more specific symptom.

9. Focus on Global and Multicultural Aspects

• The Rome IV committee expanded the criteria to ensure they are applicable globally, recognizing that IBS symptoms, triggers, and perceptions of pain can vary across cultures. The diagnostic criteria were adapted to be more inclusive of different patient populations worldwide.

Summary of Diagnostic Changes

Under Rome IV, IBS is diagnosed when:

• There is recurrent abdominal pain, occurring on average at least one day per week in the last 3 months.
• The pain is associated with two or more of the following:
  1. Related to defecation,
  2. Associated with a change in stool frequency,
  3. Associated with a change in stool form (appearance).

The Rome IV criteria also maintain that the symptoms should begin at least 6 months before diagnosis and must be chronic in nature.

These changes help clinicians identify IBS more accurately and differentiate it from other gastrointestinal disorders.