Faecal Calprotectin: What This Simple Test Reveals About Your Gut

Every year, thousands of Australians are reassured that there is nothing seriously wrong with their bowel. The cramping, diarrhoea, bloating, and urgency disrupting their daily lives are often attributed to irritable bowel syndrome (IBS). This is a functional condition that is uncomfortable but not dangerous. For many, this reassurance is accurate and appropriate. However, for a significant number of patients, the symptoms labelled as IBS may actually indicate the early or active presentation of inflammatory bowel disease (IBD). If left undiagnosed, IBD can cause progressive bowel damage and serious complications.

Until recently, the only reliable way to distinguish between IBS and IBD was through a colonoscopy. Now, a straightforward stool test called faecal calprotectin provides a critical first window into gut inflammation. This test can be done at home, without fasting, sedation, or a hospital visit.

What Is Calprotectin — and Why Does It Appear in Stool?

Calprotectin is a calcium-binding protein produced predominantly by neutrophils. These are the white blood cells your immune system deploys to sites of active inflammation. In a healthy gut, the intestinal lining is largely quiescent. Neutrophil activity is minimal, and calprotectin levels in the stool remain low. When the bowel wall becomes inflamed—whether from Crohn's disease, ulcerative colitis, an active gut infection, microscopic colitis, or certain medications—neutrophils migrate into the intestinal mucosa in significant numbers and release calprotectin.

Crucially, calprotectin is extraordinarily stable in the bowel environment. It resists breakdown by digestive enzymes and bacterial metabolism for several days at room temperature. This stability makes it well suited for stool-based measurement. A small sample collected at home, transported to a pathology laboratory, and analysed by enzyme-linked immunosorbent assay (ELISA) can provide a reliable measure of mucosal inflammation within 24 to 48 hours.

The Critical Distinction — IBS or IBD?

The symptoms of IBS and IBD overlap frustratingly. Both conditions cause abdominal pain, altered bowel habits, bloating, and urgency. They also commonly cause fatigue. In mild or early presentations, neither condition is reliably distinguishable based on clinical history and examination alone.

This is where faecal calprotectin has transformed clinical practice. IBS is a functional disorder. It produces symptoms through alterations in gut motility, visceral sensitivity, and the gut-brain axis, but it does not cause measurable inflammation of the bowel wall. In contrast, IBD involves chronic immune-mediated damage to the intestinal mucosa. Over time, this can lead to bowel scarring, stricturing, fistula formation, and a significantly increased risk of colorectal cancer.

The distinction between IBS and IBD is crucial. IBD requires active medical management, specialist gastroenterological follow-up, and often ongoing immune-modulating or biologic therapy to prevent irreversible bowel damage.

A normal faecal calprotectin result in a patient with IBS-type symptoms reduces the probability of inflammatory bowel disease to below one percent. This makes it one of the most powerful negative predictors in modern gastroenterological practice.

Research consistently confirms calprotectin's accuracy as an inflammatory marker. Meta-analyses report sensitivity of approximately 93 percent and specificity of around 96 percent for detecting active intestinal inflammation. In practical terms, a negative result substantially reduces the need for colonoscopy in low-to-moderate risk patients. This avoids an invasive procedure, reduces healthcare costs, and spares the patient significant anxiety and inconvenience.

When Should You Consider a Faecal Calprotectin Test?

Faecal calprotectin is not a routine screening test for healthy individuals without symptoms. It is most clinically useful in the following situations:

• You have ongoing bowel symptoms, including chronic diarrhoea, cramping, urgency, or blood and mucus in the stool. Your GP or gastroenterologist may want to determine whether further investigation for IBD is warranted before proceeding to colonoscopy.

• You have a confirmed diagnosis of Crohn's disease or ulcerative colitis. Your gastroenterologist may use serial calprotectin measurements to monitor disease activity, assess treatment response, and detect flares early—sometimes before symptoms visibly worsen.

• You have recovered from a gut infection, such as Campylobacter, Salmonella, Giardia, or an intestinal parasite like Dientamoeba fragilis or Blastocystis hominis, but your symptoms have persisted. Calprotectin can help distinguish ongoing mucosal inflammation from functional post-infectious IBS.

• You are being assessed for suitability for Faecal Microbiota Transplantation (FMT). In patients with ulcerative colitis or complex gut conditions, baseline and serial calprotectin measurements inform treatment timing, gauge inflammatory burden, and provide an objective marker to assess therapeutic response following the transplant.

• You have been on long-term non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen. Your gastroenterologist may want to determine whether the medication has caused bowel inflammation, a well-recognised but underdiagnosed phenomenon known as NSAID enteropathy.

  
  

Understanding Your Calprotectin Result

Results are reported in micrograms of calprotectin per gram of stool (µg/g). The interpretation, while seemingly straightforward, always requires clinical context. A result below 50 µg/g is generally considered normal. In the setting of IBS-type symptoms, it makes active IBD very unlikely. A result in the borderline range of 50 to 200 µg/g may indicate mild mucosal inflammation, medication effect, a recent gut infection, or—particularly in older patients—early colonic pathology. This range typically warrants clinical review and often repeat testing or further investigation.

A result above 200 µg/g is considered significantly elevated and strongly suggests active intestinal inflammation. At this point, colonoscopy is usually recommended to identify the underlying cause.

It is important to understand that calprotectin is a marker of inflammation, not a diagnosis. An elevated result does not automatically mean IBD. Active infection, coeliac disease, the use of NSAIDs, and colorectal polyps or malignancy can all raise levels. Equally, patients with IBD whose disease is in full mucosal remission may have a normal calprotectin. Thus, calprotectin serves as a marker of activity rather than disease presence. The result is always best interpreted by a clinician who knows your full clinical picture.

Faecal Calprotectin in IBD Monitoring and FMT

For patients with established ulcerative colitis or Crohn's disease, faecal calprotectin has become an invaluable non-invasive monitoring tool. Serial measurements—taken every three to six months, or more frequently during a suspected flare—allow gastroenterologists to track mucosal healing without repeated colonoscopies. A rising trend in calprotectin values often heralds a clinical flare before symptoms intensify. This provides a valuable window to adjust therapy proactively and prevent a full relapse.

At Mater Private, faecal calprotectin plays an important role in the assessment and monitoring of patients undergoing Faecal Microbiota Transplantation for ulcerative colitis. Baseline measurements help stratify disease activity and guide the timing and intensity of the FMT protocol. Serial post-FMT calprotectin measurements provide an objective means of tracking mucosal response, complementing symptom scores and endoscopic assessment. In patients who achieve symptomatic remission following FMT, a concurrent reduction in calprotectin offers meaningful confirmation that improvement reflects genuine mucosal healing, not simply a subjective shift in how symptoms are perceived.

FMT for ulcerative colitis at Mater Private is delivered as a structured six-month program. This uses three delivery methods—fresh enema, capsule-based FMT, and transcolonic infusion—tailored to the individual patient's disease characteristics. Calprotectin monitoring is integrated throughout the program to guide decisions about additional infusion cycles and to define the endpoint of treatment response.

Practical Considerations: How the Test Works

The practical process of collecting a faecal calprotectin sample is straightforward. A small stool sample—roughly the size of a pea—is collected into a provided container using an enclosed scoop. The sample does not require any dietary preparation, fasting, or bowel preparation beforehand. It is stable at room temperature for up to three days, meaning it can be posted to a pathology laboratory if a local drop-off is not convenient. Results are typically available within 24 to 48 hours of the sample reaching the laboratory.

Your gastroenterologist or GP will interpret the result in the context of your full clinical picture. This includes your symptom history, age, family history of bowel disease, current medications, and any prior investigations. A single elevated result should never be viewed in isolation. The trend over serial measurements—and the clinical context in which the elevation occurs—matter as much as any individual value. Calprotectin is a powerful tool when used appropriately; like any test, its value is amplified by expert clinical interpretation.

When to Seek a Specialist Opinion

If you have been living with persistent gut symptoms—bloating, diarrhoea, cramping, urgency, or unexplained fatigue—and have not yet had a faecal calprotectin measurement, it is worth discussing this with your GP. If your result is elevated, or if you have already received a diagnosis of inflammatory bowel disease and are struggling with ongoing symptoms or treatment side effects, a specialist gastroenterological opinion can significantly change the course of your management.

Dr. Jeffrey Tu consults at Mater Private and specialises in the investigation and management of complex gut conditions. This includes inflammatory bowel disease, intestinal parasites, H. pylori, and SIBO. For patients with IBD who are not responding adequately to conventional therapy, FMT represents an evidence-based treatment option available as part of a structured, medically supervised program. To arrange a referral, speak with your GP about a specialist gastroenterology appointment. Your gut health is worth investigating thoroughly, and an accurate diagnosis is the essential first step toward effective treatment.