Introduction Faecal calprotectin (FC) has been shown to distinguish reliably between functional and inflammatory bowel diseases (IBD) in a number of studies of patients with established gastrointestinal disease. However, it is a poor screening test for colorectal cancer. Presently, diagnostic algorithms incorporating FC at first presentation to the gastroenterology clinic are lacking.
Methods This study aimed to determine the optimal use of FC, in conjunction with serum markers, in the initial diagnostic workup of patients aged 16–50 years. Patients >50 years were excluded, as they require colonoscopy to exclude malignancy. Detailed clinical, laboratory, endoscopic and radiological parameters were collected. Patients with a prior GI diagnosis were excluded. All stool samples were analysed in the same laboratory using the same FC assay (Calpro ELISA). ROME III and Lennard-Jones criteria were used. Patients were followed up for a minimum of 12 months.
Results The Edinburgh FC Register comprises data on 7512 patients (2005–2008) from across Lothian. 1838/7512 were managed at 2 Edinburgh teaching hospitals, and aged 16–50 years at time of FC; 851 were excluded, mostly due to pre-established diagnosis of IBD. 987 (mean±SD age 33.5±9.0 years; 64.8% female) met the strict inclusion criteria. In patients presenting primarily with bloody diarrhoea (n=68), median FC was 690 μg/g (IQR: 72–2323), in contrast to watery diarrhoea (n=325, FC 30 μg/g (20–90), p<0.0001), or abdominal pain (n=271; FC 25 μg/g (20–85), p<0.0001). 193/987 (19.6%) were ultimately diagnosed with organic disease with median FC of 180 μg/g (37–1292), 113/987 (11.4%) with IBD (FC 990.0 (225–2190)) and 605/987 (61.3%) with a functional disorder (FC 20 (20–50)). FC was influenced by NSAID use, but not by age, sex or smoking. ROC analysis of FC in discriminating organic disease and IBD from functional disorders gave an area under the curve of 0.80 (95% CI 0.76 to 0.84) and 0.93 (95% CI 0.90 to 0.96), respectively. Further detailed analysis suggested the following model: FC<70 μg/g with normal blood parameters and no alarm symptoms/signs – no further investigation; FC>50 μg/g with bloody diarrhoea OR raised CRP/low albumin – combined radiological and endoscopic evaluation.
Conclusion In this study, the largest on the clinical utility of FC, we were able to develop clear investigative strategies in adults <50 years, dependent on FC and other clinical/laboratory parameters. This simple algorithm could be rolled out into primary care facilitating timely and appropriate triage of new patients and minimising diagnostic delay in IBD.
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