Supplementary graphs not presented on the poster show that 88.6% of calprotectin results fell between the first and second result in patients that subsequently had IBD excluded: It also demonstrates that 83% of patients with an increase between their first and second calprotectin test were subsequently found to have IBD. Although the overall statistics are compelling, interpretation is not always straightforward as Dr Rimmer explains: “We certainly feel that the faecal calprotectin (FCAL) is a highly accurate test but there are some inconsistencies and pitfalls, which to an extent the graph represents: • The FCAL is just a snapshot from a single time point. In acute infection it will be high but if symptoms improve and FCAL normalises then investigation isn’t needed – post infective IBS is common in this patient group. • However, IBD is also characterised by periods of relapse and remission and FCAL will fluctuate alongside this, occasionally by the time we come to investigate they may have entered a milder phase of the disease. The clinical history and duration of symptoms in these patients is important, particularly with Crohn’s disease where the symptoms can be more insidious. Z We also had a handful of patients with mild proctitis in our cohort would not have been picked up with FCAL alone as their inflammation had largely resolved by the time we saw them. • FCAL will on rare occasions fail to correlate with disease severity, in the majority of our patients that was in ileal Crohn’s disease. Again, careful attention to the clinical history is necessary and investigation required regardless of the FCAL result in those with progressive symptoms or concerning features such as weight loss.” A variety of cut-off values were assessed on the poster, and two results of >200µg/g gave the best performance overall with a 85.7 PPV% , 86.2 NPV% and a specificity of 89.5% but the sensitivity was lower than other cut-off values at 81.5%. The poster concluded that the data, in general, supports repeat FCAL testing to avoid unnecessary investigations adding to post COVID endoscopy backlogs. A cut-off of two values >200µg/g had the best overall performance but can miss a small number of IBD cases, particularly those with isolated ileitis or more indolent disease course. This cut-off should not be used in those with a marked increase between the 1st and 2nd result, where IBD is likely. Modifications to the local referral pathway are currently being determined, taking into account the data generated in the study. This will hopefully enable better use of over stretched resources which should in turn result in quicker access to those with most need. For more information on Faecal Calprotectin Testing please visit: www.calprotectin.co.uk www.alphalabs.co.uk © 2023 Copyright Alpha Laboratories Ltd. 3
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