Calprotectin levels measured in stool samples could be an effective way of identifying spondyloarthritis patients at risk of bowel inflammation, researchers say.

The research team from Belgium noted that microscopic bowel inflammation was associated with more severe disease and was present in up to half of all people with spondyloarthritis (SpA).

However, no reliable biomarkers existed to identify the patients at most risk.

Calprotectin is a sensitive marker of neutrophilic inflammation and is used by gastroenterologists to discriminate between IBD and IBS, although its absence from the MBS has limited uptake of the test in Australia.

Related story: Calls to fund faecal calprotectin

In the current study of 125 people with SpA those with elevated levels of CRP and serum calprotectin had a frequency of bowel inflammation of 64% compared to 25% in patients with low levels.

Faecal calprotectin provided the best sensitivity and specificity for detection of bowel inflammation as a single marker, however disadvantages included patient reluctance to collect stool samples and the fact that NSAID use interfered with levels.

When either CRP or serum calprotectin was elevated, the risk was intermediate (40%) and measuring faecal calprotectin provided further differentiation, the researchers reported in the study published in the Annals of the Rheumatic Diseases.

Because of this finding the researchers suggested adopting a screening approach where initially serum calprotectin and CRP are assessed and, if necessary, faecal calprotectin.

The model using this scenario provided an area under the ROC curve of 74.4% for detection of bowel inflammation.

“Serum and faecal calprotectin measurements in addition to CRP may be useful in identifying patients with SpA at higher risk of subclinical bowel inflammation who might benefit from further invasive checkup” they concluded.