What is the fecal laboratory test to differentiate between Inflammatory Bowel Disease (IBD)?

From the Guidelines

Fecal calprotectin is the primary laboratory test used to differentiate between Inflammatory Bowel Disease (IBD) and non-inflammatory conditions like Irritable Bowel Syndrome (IBS). This non-invasive stool test measures the level of calprotectin, a protein released by neutrophils during intestinal inflammation. Elevated levels (typically >50-100 μg/g, though cutoff values may vary between laboratories) suggest active inflammation in the intestines, which is characteristic of IBD conditions like Crohn's disease and ulcerative colitis, rather than functional disorders 1.

The test is particularly useful as a screening tool before more invasive procedures like colonoscopy are considered. Fecal calprotectin has good sensitivity and specificity for detecting intestinal inflammation, with higher levels generally correlating with more severe disease activity 1. The test can also be used to monitor disease activity and response to treatment in patients with established IBD. Patients should follow collection instructions carefully and be aware that certain medications like NSAIDs can affect results by causing mild intestinal inflammation.

Some key points to consider when using fecal calprotectin include:

• A normal level has a very high negative predictive value for IBD, making it a useful tool for ruling out the condition 1
• The positive predictive value of levels above the assay reference level is low, and a higher threshold (generally between 100 and 250 μg/g stool) should be used to trigger colonoscopy 1
• Fecal calprotectin is not sensitive enough to exclude advanced colorectal adenoma or colorectal carcinoma, and cancer pathway referral should be strongly considered in patients with rectal bleeding and abdominal pain, change in bowel habit, weight loss, or iron-deficiency anaemia 1
• The test is not appropriate for patients with acute diarrhoea due to infection, as calprotectin levels may be raised and will not discriminate between IBD and gastroenteritis 1

Overall, fecal calprotectin is a valuable tool in the diagnosis and management of IBD, and its use can help reduce unnecessary colonoscopy and improve patient outcomes 1.

From the Research

Fecal Laboratory Tests for Inflammatory Bowel Disease (IBD)

The following fecal laboratory tests can be used to differentiate between Inflammatory Bowel Disease (IBD) and other conditions:

• Fecal calprotectin test: This test measures the level of calprotectin in stool, which is a protein that is found in the stool of people with IBD 2, 3, 4, 5.
• Fecal lactoferrin test: This test measures the level of lactoferrin in stool, which is a protein that is found in the stool of people with IBD 6.

Accuracy of Fecal Calprotectin Tests

The accuracy of fecal calprotectin tests in differentiating IBD from other conditions is as follows:

• Quantum Blue® Calprotectin: 94% accurate in differentiating IBD from irritable bowel syndrome (IBS) and 91% accurate in differentiating IBD from other colitis 2.
• EliA™ Calprotectin: 92% accurate in differentiating IBD from IBS and 89% accurate in differentiating IBD from other colitis 2.
• RIDASCREEN® Calprotectin: 82% accurate in differentiating IBD from IBS and 76% accurate in differentiating IBD from other colitis 2.
• LIAISON Calprotectin Assay: 92.2% sensitive and 88.4% specific in distinguishing IBD from other GI disorders 5.

Cutoff Values for Fecal Calprotectin Tests

The cutoff values for fecal calprotectin tests are as follows:

• Quantum Blue® Calprotectin: 50 µg/g 2.
• EliA™ Calprotectin: 50 µg/g 2.
• RIDASCREEN® Calprotectin: 50 µg/g 2.
• LIAISON Calprotectin Assay: 94 µg/g 5.
• General cutoff value: 100 µg/g 5.