Fecal Calprotectin Test for IBD

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When symptoms like ongoing diarrhoea, abdominal pain, or blood in stool raise the possibility of IBD, doctors may use a fecal calprotectin test to look for inflammation in the gut.

What Fecal Calprotectin Measures

The Fecal calprotectin test measures the amount of calprotectin in a stool sample. Calprotectin is a protein released by certain white blood cells when there is inflammation in the intestines. Higher levels can suggest active intestinal inflammation, which may occur with Crohn’s disease or Ulcerative colitis. However, the result alone cannot confirm IBD because other factors can also raise calprotectin levels.

Why Doctors Order It

Doctors can order calprotectin tests when there is ongoing inflammation in the intestine. It can help when symptoms such as diarrhoea, abdominal pain, or blood in stool occur.

• It supports the evaluation of IBD.
• It checks whether inflammation is active.
• It monitors how the bowel is responding to treatment.
• It looks for signs of inflammation when symptoms are not clear.
• It helps doctors determine whether further tests like colonoscopy are needed or not.

How The Sample Is Collected

A Faecal calprotectin test requires a small stool sample. You can collect it by yourself in a small, clean container provided by the laboratory. The stool sample should not mix with toilet water, urine, or toilet paper. After collecting the required amount, close the container properly and label your name and date on the container. Wash your hands with soap and water. Follow the lab instructions on storage and how soon the sample should be submitted. 

How Results Are Interpreted

Faecal calprotectin results are usually reported as a calprotectin level in the stool. Lower levels generally suggest little or no intestinal inflammation, while higher levels may indicate active inflammation. False-negative calprotectin happens in children; results show normal levels when your intestines are inflamed. The exact cut-offs can vary between laboratories, so doctors interpret the result using the lab reports alone with symptoms and other lab reports. But raised levels do not automatically mean that there is confirmed IBD. 

Reasons A Level May Be Raised

A raised calprotectin level usually shows inflammation in the digestive tract, but IBD is not the only reason; levels may also increase due to: 

• Crohn’s disease or ulcerative colitis
• Intestinal infections due to bacteria and viruses
• Certain medicines such as NSAIDs
• Gastrointestinal bleeding 
• Colorectal cancer

Medicines That May Affect Results

Some medicines can increase fecal calprotectin levels and affect how the results are interpreted:

• NSAIDs (Nonsteroidal Anti-inflammatory Drugs) such as ibuprofen, naproxen, diclofenac, and aspirin.
• PPIs (Proton Pump Inhibitors) such as lansoprazole, omeprazole, and pantoprazole. 
• Anti- inflammatory or immune-modulating drugs. 

Some medicines may also affect gut inflammation with test levels, so tell your doctor about every medicine or supplement you take. And do not stop taking the prescribed medicines without your doctor’s advice. 

Calprotectin In Flare Monitoring

Faecal calprotectin helps doctors check whether intestinal inflammation is active during an IBD Flare. The test measures a protein released by white blood cells into the stool to accurately detect intestinal inflammation. A rise in the level may suggest increasing inflammation, while a fall over time can indicate the inflammation is settling with the treatment.

• Less than 50 to 100 quiescent shows that the inflammation is inactive.
• Results between 100 to 250 quiescent show that the inflammation is mild.
• More than 250 quiescent shows that there is active mucosal inflammation, or an impending flare.

Why One Test Is Not A Diagnosis

Fecal calprotectin is a biomarker test, not a standalone test for IBD. It only shows that elevated calprotectin markers mean there is inflammation present somewhere in the digestive tract, and it cannot show the correct location of the inflammation and the reason behind it. It may show false or negative results; raised levels could be triggered by mild infection. It cannot confirm whether it is Crohn’s disease or ulcerative colitis. That's why doctors use other tests such as blood tests, imaging tests, and medical history along with symptoms to diagnose IBD.

Infection

Intestinal infection can raise fecal calprotectin levels because the body releases immune cells to fight the infection, causing inflammation in the gut. Infections caused by certain bacteria and other germs may produce symptoms similar to an IBD flare, such as diarrhoea, abdominal pain, and fever. Doctors may recommend stool tests to check for infection before deciding whether the symptoms are related to IBD. 

What May Happen Next

What happens after a Fecal calprotectin test depends on the results and the symptoms. If the levels are low, your doctor may consider other causes and symptoms or continue monitoring. If the test levels are raised, doctors may consider further tests such as blood tests and imaging tests, including ultrasound, colonoscopy, or biopsy to find the exact cause. For someone already diagnosed with IBD, it may help with further treatment, and repeated tests may be suggested during the treatment process. 

Repeat Testing

Doctors may suggest repeating the fecal calprotectin test when the result is unclear, when test levels are borderline, or when they want to see how inflammation is changing over time. In people with IBD, repeated testing can help monitor the response to treatment and check ongoing inflammation. The timing depends on the symptoms, previous symptoms, and treatment plan.

Local Laboratory Ranges

• Calprotectin results can be reported using different cutoff values, depending on the laboratory and the test method.
• A result slightly above the lab’s range may not always mean active IBD.
• Lab reports rely on specific age reference scales; young children naturally have much higher baselines.
• Anti- inflammatory drugs artificially inflate calprotectin levels.
• Always check the reference range given on your laboratory report. 
• Doctors interpret your test levels with your symptoms and other test results.

Reference 

Calprotectin Stool Test: MedlinePlus Medical Test

The Use of Fecal Calprotectin in Inflammatory Bowel Disease - PMC

Calprotectin as a Biomarker for Infectious Diseases: A Comparative Review with Conventional Inflammatory Markers - PMC

Guidance on the interpretation of faecal calprotectin levels in children - PMC