What are the diagnostic criteria for Irritable Bowel Syndrome (IBS) with constipation (IBS-C)?

From the Guidelines

Diagnosing IBS with constipation (IBS-C) should be based on the Rome IV criteria, which include recurrent abdominal pain at least one day per week for the past three months, associated with two or more of the following: pain related to defecation, change in stool frequency, or change in stool form/appearance, as stated in the 2021 British Society of Gastroenterology guidelines 1. To diagnose IBS-C, the following criteria should be met:

• Recurrent abdominal pain at least one day per week for the past three months
• Associated with two or more of the following:
  • Pain related to defecation
  • Change in stool frequency
  • Change in stool form/appearance
• More than 25% of bowel movements should involve hard or lumpy stools and less than 25% should be loose or watery The diagnosis of IBS-C requires a thorough medical evaluation by a healthcare provider, including a detailed medical history, physical examination, and tests to rule out other conditions that can cause similar symptoms, such as blood tests, stool tests for infections or inflammation, and possibly a colonoscopy depending on age and risk factors 1. A food and symptom diary can be helpful to identify triggers, and red flag symptoms that might indicate a different condition include unexplained weight loss, rectal bleeding, family history of colorectal cancer or inflammatory bowel disease, and onset of symptoms after age 50. It's worth noting that the Rome IV criteria are more restrictive than the Rome III criteria, which may lead to some patients not meeting the criteria for IBS-C, but instead being diagnosed with another functional bowel disorder, as mentioned in the 2021 British Society of Gastroenterology guidelines 1. However, the NICE guideline definition of IBS may be preferable in primary care settings, as it is less restrictive and can provide a clearer diagnosis and management options for patients with troublesome symptoms, as stated in the 2021 British Society of Gastroenterology guidelines 1.

From the FDA Drug Label

All patients met Rome II criteria for IBS and were required, during the 2-week baseline period, to meet the following criteria: a mean abdominal pain score of at least 3 on a 0-to-10-point numeric rating scale less than 3 complete spontaneous bowel movements (CSBMs) per week [a CSBM is a spontaneous bowel movement (SBM) that is associated with a sense of complete evacuation; a SBM is a bowel movement occurring in the absence of laxative use], and less than or equal to 5 SBMs per week.

To diagnose IBS with constipation, the following criteria should be met:

• Rome II criteria for IBS
• Mean abdominal pain score of at least 3 on a 0-to-10-point numeric rating scale
• Less than 3 complete spontaneous bowel movements (CSBMs) per week
• Less than or equal to 5 spontaneous bowel movements (SBMs) per week 2

From the Research

Diagnostic Criteria for IBS with Constipation

To diagnose IBS with constipation, the following criteria are considered:

• Abdominal pain and altered bowel habits are cardinal symptoms of IBS, as stated in 3
• The Rome IV criteria are widely used for diagnosing functional gastrointestinal disorders, including IBS with constipation, as mentioned in 4, 5, and 3
• A thorough review of the patient's symptoms, medical history, and physical examination are essential for diagnosis, as outlined in 6 and 3

Diagnostic Approach

The diagnostic approach for IBS with constipation involves:

• Evaluating the patient for warning signs, such as anemia, hematochezia, unintentional weight loss, or a family history of colorectal cancer or inflammatory bowel disease, as mentioned in 3
• Using the Rome IV criteria to guide diagnosis, as stated in 4, 5, and 3
• Considering the presence of abdominal pain, bloating, and bowel habits, as mentioned in 4 and 7

Diagnostic Tests and Referral

Diagnostic tests and referral criteria include:

• Colonoscopy based on alarm symptoms or age, as recommended in 7
• Limited diagnostic testing, such as blood tests and imaging studies, to rule out other medical conditions, as mentioned in 6
• Referral to a specialist, such as a gastroenterologist, if symptoms persist or worsen, as mentioned in 4

Challenges in Diagnosis

Challenges in diagnosing IBS with constipation include:

• Overlapping and fluctuating symptoms with functional constipation, as mentioned in 7
• Inconsistent and regional variations in diagnostic criteria, as identified in 7
• The need for comprehensive characterizations of pain and constipation in both IBS with constipation and functional constipation, as stated in 7