Simple screening test reduces invasive examinations for suspected bowel disease

Endoscopy is a procedure that involves passing a camera on the end of a flexible tube through the rectum to examine the bowel.

Rates of inflammatory bowel disease are rising in both adults and children. The major types are Crohn's disease and ulcerative colitis and symptoms can include abdominal pain, diarrhoea, rectal bleeding and weight loss.

A diagnosis is generally made using endoscopy and taking small tissue samples (biopsies), but this process is expensive, invasive and time consuming and, for many patients, the results are negative.

A simple, non-invasive and cheap screening test would help doctors identify patients who are most likely to have inflammatory bowel disease and thus avoid unnecessary endoscopies in other patients.

Measuring calprotectin levels (a protein found in inflammatory cells) in stools could be a good screening test, but its accuracy is largely unknown.

So researchers based in the Netherlands set out to determine whether faecal calprotectin can serve as a screening test to limit the number of people undergoing invasive endoscopy.

They analysed the results of six adult (670 patients) and seven child studies (371 patients) comparing faecal calprotectin with endoscopy in patients with suspected inflammatory bowel disease.

Inflammatory bowel disease was confirmed in 32% of the adults and 61% of the children

Screening with faecal calprotectin reduced the number of endoscopies by 67% in adults and 35% in children, but it also delayed diagnosis in 6% (2 in 32) of the affected adults and 8% (5 in 61) of the affected children.

The clinical consequences of missing patients with inflammatory bowel disease should be balanced against those patients without the disease who are subjected to endoscopy, say the authors.

Despite some differences in the design and quality of the studies, they conclude that faecal calprotectin is a useful screening tool for identifying patients who are most likely to need endoscopic evaluation for suspected inflammatory bowel disease.

The ability of the test to safely exclude inflammatory bowel disease (its specificity) is significantly better in adult studies than in paediatric studies, they add.

In an accompanying editorial, Robert Logan, consultant gastroenterologist at Kings College Hospital in London says that these findings support more widespread use of the test in secondary care, but that there is not yet enough evidence to support its use in primary care.

"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 inflammatory bowel disease is diagnosed," he writes.