Diagnostic Criteria

Many doctors, including gastroenterologists, may refer to the general definition of IBS provided by the American College of Gastroenterology to determine a diagnosis of IBS. The American College of Gastroenterology defines IBS as general abdominal pain with disordered defecation. However, more detailed guidelines, primarily the Rome III criteria and Manning criteria, may be used for diagnosis of IBS. Despite the detailed guidelines, none of these methods are ideal.¹

Rome III criteria

The Rome III criteria are commonly used in research studies, but not used in clinical practice.¹ It was first developed based on a meeting held in Rome to standardize a guideline for the diagnosis of IBS. The Rome III criteria is based on pain symptoms and considers pain to be the primary symptom of IBS.² The Rome III criteria require recurrent abdominal pain or discomfort at least 3 days/month in the last 3 months, which is associated with two or more of the following:³

• Improvements with defecation
• Onset associated with a change in frequency of stool
• Onset associated with a change in form or appearance of stool

It should be noted that “discomfort” means an uncomfortable sensation that’s not described as pain.³

Based on the Rome III criteria and the Bristol Stool Scale, IBS may be subtyped on the basis of a person’s stool characteristics.⁴ However, the Rome III criteria is not well validated and is not a preferred method to discriminate IBS from other chronic intestinal diseases.²

Manning criteria

Some studies suggested that the Rome III criteria demonstrated low validity and that the Manning criteria were more widely validated for clinical use.^2,4 In 1978, the Manning criteria was initiated as an objective method to diagnose IBS. The criteria stated that there were four symptoms significantly more common in people with IBS, including:^2,5

• Abdominal pain relief with bowel movement
• Visible distention
• More frequent stools with the onset of pain
• Looser stools with the onset of pain.

Over time, two additional symptoms were found to be of increased prevalence in IBS and were added to the Manning criteria. The symptoms were fecal mucus and sensation of incomplete evacuation. Presently, these six symptoms are known as the Manning criteria. Unlike the Rome III criteria, the Manning criteria does not provide a method to differentiate between diarrhea-predominant IBS from constipation-predominant IBS.²