Fecal Calprotectin a Sign of Inflammatory Bowel Disease

July 22, 2010 — A new approach to the diagnosis of inflammatory bowel disease (IBD) — fecal calprotectin testing — is a useful tool for identifying patients who are most likely to need endoscopy for suspected IBD, thereby reducing the number of unnecessary endoscopies, according to a meta-analysis published online July 16 in the British Medical Journal.

"Endoscopic evaluation with histopathological sampling is generally considered indispensable in the investigation of patients with suspected [IBD]," write Patrick F. van Rheine, MD, from Beatrix Children's Hospital, University Medical Center Groningen, the Netherlands, and colleagues. "In a relatively large proportion of people with suspected [IBD,] the results of endoscopy will be negative."

The aim of this meta-analysis was to evaluate whether adding fecal calprotectin testing to the work-up of patients with suspected IBD would reduce the number of unnecessary endoscopies.

Calprotectin is a major protein found in inflammatory cells. It is stable in stool samples for up to 7 days at room temperature, and 1 sample of less than 5 g is sufficient to allow for reliable measurement.

The analysis included 13 prospective studies that compared fecal calprotectin testing with endoscopy as the reference test. Six were done in adults (n = 670), and 7 in children and teenagers (n = 371).

IBD was confirmed in 32% (n = 215) of the adults and in 61% (n = 226) of the children and teenagers. In adults, the pooled sensitivity of fecal calprotectin testing was 0.93 (95% confidence interval [CI], 0.85 - 0.97), and the pooled specificity was 0.96 (95% CI, 0.79 - 0.99). In children and teenagers, the pooled sensitivity was 0.92 (95% CI, 0.84 - 0.96), and the pooled specificity was 0.76 (95% CI, 0.62 - 0.68).

The lower specificity in children and teenagers was significantly different from that in adults (P = .048).

The authors report that screening with fecal calprotectin would reduce the number of adults requiring endoscopy by 67%. They add that 3 of 33 adults who undergo endoscopy will not have IBD but may have a different condition that would still necessitate having an endoscopy.

In children and teenagers, screening with fecal calprotectin would reduce the number of endoscopies by 35%.

However, the downside of such screening would be a delayed diagnosis in 6% (2/32) of affected adults and in 8% (5/61) of affected children because of false-negative test results.

The authors write that the clinical consequences of missing patients with IBD should be balanced against patients without the disease being subjected to endoscopy. A false-negative fecal calprotectin test would lead to delayed treatment and continuation of symptoms, whereas a false-positive test would lead to an unnecessarily invasive endoscopy with possible complications from colonic perforation or tear and anesthesia.

The researchers also point out methodological limitations of their meta-analysis. Two of the included studies in adults did not sample intestinal mucosa, which might have caused some patients to be misclassified as normal. In addition, none of the studies used a well-defined set of clinical findings or flow chart to identify patients with a high probability of IBD. In addition, the number of studies included in the meta analysis was limited, and the studies were restricted to those written in English.

Despite these limitations, the study demonstrates that measuring fecal calprotectin levels is a useful screening tool for identifying patients most likely to need endoscopy, and the test can contribute important information to guide patient management at a tertiary-care level, the authors write.

Finally, they note that the pooled sensitivity and specificity found in their study should be interpreted with caution. "Despite a strict selection of studies based on proper patient recruitment and study design, heterogeneity was considerable."

In an accompanying editorial, Robert Logan, MD, from Kings College Hospital, London, United Kingdom, writes that the sensitivity of 93% and specificity of 96% of the fecal calprotectin test is remarkable, "considering the diverse and complex antigenic environment of faeces."

However, the test cannot be recommended as a diagnostic test for IBD in primary care because the results of the study apply to patients referred to secondary care. In primary care, patient characteristics and populations are "probably different," which would affect the negative and positive predictive value of fecal calprotectin screening.

"If studies conducted in primary care find a high diagnostic accuracy of the faecal calprotectin test it will be an important step forward in how [IBD] is diagnosed," he concludes.

The study authors and Dr. Logan, the editorialist, have disclosed no relevant financial relationships.