Document resource
Introduction Coeliac disease (CD) frequently presents with non-specific gastrointestinal symptoms that overlap with irritable bowel syndrome (IBS), posing a diagnostic challenge in primary care. Non-invasive biomarkers are commonly used in the initial assessment of patients with IBS-like symptoms, with faecal calprotectin (FC) widely employed to distinguish inflammatory bowel disease (IBD) from functional disorders. However, existing literature on the role of FC in CD diagnosis remains conflicting. This study firstly aimed at assessing the diagnostic sensitivity of FC for active CD by evaluating the relationship between FC levels, coeliac serology, and histological severity in newly diagnosed adult patients with CD. As a secondary objective, we examined longitudinal changes in FC following initiation of a gluten-free diet.Methods We analysed paired serological and faecal samples from 129 newly diagnosed adult CD patients (mean age 35.0 ± 14.6 years). Duodenal biopsies were graded using the Marsh-Oberhuber classification. A sub-cohort of 35 patients provided follow-up samples after GFD initiation. We assessed the diagnostic sensitivity of FC and its correlation with tTG-IgA titers and mucosal atrophy.Results The majority of untreated CD patients presented with normal or mildly elevated FC levels with a diagnostic sensitivity of 32.6% (42/129), using the standard clinical cut-off of >50 µg/g. Furthermore, only 7.8% of patients presented with markedly elevated levels typically indicative of IBD (>200 µg/g). However, a weak but statistically significant positive correlation with serum tTG-IgA was observed ( rho = 0.215, p = 0.015). Histological analysis revealed that FC levels could differentiate the extremes of the disease spectrum with no significant difference across intermediate Marsh grades. Indeed, median levels, even remaining within the reference range, were significantly higher in patients with total villous atrophy (Marsh 3c: 36.5 µg/g) compared to those with Potential CD/normal histology (Marsh 0: 16.5 µg/g; p = 0.02). Longitudinally, in patients with elevated baseline FC, adherence to a GFD was associated with a trend toward normalization, with median levels decreasing from 102.5 µg/g to 46.5 µg/g (p = 0.059).Discussion This study observes that FC has a minor role in ruling out uncomplicated CD in patients presenting with IBS-like symptoms in primary care. Although FC levels show a weak association with serological and histological disease severity, the elevation is generally within the normal reference range. Therefore, mild FC elevation should raise clinical suspicion for CD leading to appropriate serological testing, whereas markedly elevated FC values should prompt investigation for alternative pathology, particularly IBD or complicated CD, rather than being attributed to CD alone.Abstract P373 Figure 1