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Test accuracy of faecal calprotectin for inflammatory bowel disease in UK primary care : a retrospective cohort study of the IMRD-UK data
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Freeman, Karoline, Taylor-Phillips, Sian, Willis, Brian H., Ryan, Ronan and Clarke, Aileen (2021) Test accuracy of faecal calprotectin for inflammatory bowel disease in UK primary care : a retrospective cohort study of the IMRD-UK data. BMJ Open, 11 (2). e044177. doi:10.1136/bmjopen-2020-044177 ISSN 2044-6055.
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Official URL: http://dx.doi.org/10.1136/bmjopen-2020-044177
Abstract
Objective: To estimate the test accuracy of faecal calprotectin (FC) for inflammatory bowel disease (IBD) in the primary care setting using routine electronic health records.
Design: Retrospective cohort test accuracy study.
Setting: UK primary care.
Participants: 5970 patients (≥18 years) without a previous IBD diagnosis and with a first FC test between 1 January 2006 and 31 December 2016. We excluded multiple tests and tests without numeric results in units of µg/g.
Intervention: FC testing for the diagnosis of IBD. Disease status was confirmed by a recorded diagnostic code and/or a drug code of an IBD-specific medication at three time points after the FC test date.
Main outcome measures: Sensitivity, specificity, and positive and negative predictive values for the differential of IBD versus non-IBD and IBD versus irritable bowel syndrome (IBS) at the 50 and 100 µg/g thresholds.
Results: 5970 patients met the inclusion criteria and had at least 6 months of follow-up data after FC testing. 1897 had an IBS diagnosis, 208 had an IBD diagnosis, 31 had a colorectal cancer diagnosis, 80 had more than one diagnosis and 3754 had no subsequent diagnosis. Sensitivity, specificity, and positive and negative predictive values were 92.9% (88.6% to 95.6%), 61.5% (60.2% to 62.7%), 8.1% (7.1% to 9.2%) and 99.6% (99.3% to 99.7%), respectively, at the threshold of 50 µg/g. Raising the threshold to 100 µg/g missed less than 7% additional IBD cases. Longer follow-up had no effect on test accuracy. Overall, uncertainty was greater for specificity than sensitivity. General practitioners’ (GPs’) referral decisions did not follow the anticipated clinical pathways in national guidance.
Conclusions: GPs can be confident in excluding IBD on the basis of a negative FC test in a population with low pretest risk but should interpret a positive test with caution. The applicability of national guidance to general practice needs to be improved.
Item Type: | Journal Article | ||||||||
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Subjects: | R Medicine > RA Public aspects of medicine R Medicine > RC Internal medicine |
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Divisions: | Faculty of Science, Engineering and Medicine > Medicine > Warwick Medical School > Health Sciences Faculty of Science, Engineering and Medicine > Medicine > Warwick Medical School |
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Library of Congress Subject Headings (LCSH): | Inflammatory bowel diseases , Inflammatory bowel diseases -- Immunological aspects, Inflammatory bowel diseases -- Treatment, Feces -- Analysis, Feces -- Examination | ||||||||
Journal or Publication Title: | BMJ Open | ||||||||
Publisher: | BMJ | ||||||||
ISSN: | 2044-6055 | ||||||||
Official Date: | 22 February 2021 | ||||||||
Dates: |
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Volume: | 11 | ||||||||
Number: | 2 | ||||||||
Article Number: | e044177 | ||||||||
DOI: | 10.1136/bmjopen-2020-044177 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||
Date of first compliant deposit: | 21 April 2021 | ||||||||
Date of first compliant Open Access: | 21 April 2021 | ||||||||
RIOXX Funder/Project Grant: |
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