There’s more evidence that faecal calprotectin (FC) testing is clinically useful in differentiating between IBD or organic gastrointestinal disease (GID) and functional GID. 

A systematic review identified 18 studies that met eligibility criteria for relevance and quality. FC was assessed using the standard ELISA method and cut-off values of either 50 ug/g or 100 ug/g.

The meta-analysis of 15 studies comparing organic GID and functional GID found that FC testing had a high sensitivity (81%) and specificity (81%).

In 10 studies where FC testing was used to distinguish between IBD alone and functional GID,  FC testing was slightly more sensitive (88%) and less specific (72%).

Combined across all 18 studies, FC testing to distinguish IBD or organic GID from functional GID was a reliable 80% sensitive and 81% specific. 

The positive predictive value was calculated at 4.2% and the negative predictive value at 100%.

The researchers said in the MJA that the main benefits of FC testing would be to confirm a clinical diagnosis of a functional GID without the need for more expensive investigations such as cross-sectional imaging and colonoscopy. 

“Given its high predictive value (100%) in low prevalence populations, (0.1-1% for organic GID), FC testing is suitable for primary care screening of patients for organic GID, although, given its low positive predictive value, further investigation will be required for patients with elevated FC levels.”

FC screening also reduced the risk of missing an organic GID and allowed for prompt review by a specialist, they said.  

The study found the diagnostic accuracy of FC testing was not significantly different when using the 50 μg/g or 100 μg/g cut-offs. 

“Nevertheless, the lower cut-off is appropriate, given the role of FC testing as a screening test for organic GIDs.”

First author and gastroenterologist Dr Yoon An, from Mater Health in Brisbane, told the limbic a negative faecal calprotectin alone was very useful to confidently rule out pathology. 

However intestinal ultrasound also offered an additional layer of non-invasive investigation.

“If you have faecal calprotectin and intestinal ultrasound negative then we are definitely not doing any invasive colonoscopy to investigate this further,” she said.

She said local training in intestinal ultrasound would become available in Australia from next year which would help improve access to a new way of triaging patients and also monitoring disease activity in people with IBD.

The study noted that FC testing has consistently been associated with cost savings compared to colonoscopy.

“Reducing the number of referrals of patients with functional gastrointestinal symptoms to public health secondary care allows limited clinical resources to be used more effectively and appropriately,” it said.

In its 2018 rejection of faecal calprotectin testing for MBS listing, the Medical Services Advisory Committee (MSAC) said it acknowledged the clinical need for a diagnostic triage test to differentiate IBD from IBS in order to avoid some of the more invasive subsequent investigations such as colonoscopies.

However it said it had a number of concerns such as “…unfavourable and highly uncertain cost-effectiveness, and likely large financial implications with little confidence that utilisation can be kept within the intended purposes and consequences.”

Dr An said the systematic review should strengthen the case for MBS listing when it was next considered.