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Poster presentations: Microbiology 2020

P852 Introduction of Entamoeba histolytica serology testing in the management of inflammatory bowel disease patients at University Hospitals of Leicester, UK

D. O’Meara1, Q. Tufail1, F. Lim2, C. Richards3, A.A. Thi1

1University Hospitals of Leicester, Digestive Diseases Centre, Leicester, UK, 2University Hospitals of Leicester, Microbiology, Leicester, UK, 3University Hospitals of Leicester, Histopathology, Leicester, UK

Background

Amoebic colitis can mimic inflammatory bowel disease (IBD) in clinical presentation, endoscopic and (to some extent) histological findings. Four patients with amoebic colitis were misdiagnosed with IBD or an IBD flare at University Hospitals of Leicester (UHL), UK in 2018. This prompted a change in practise in our department and we began screening for Entamoeba histolytica in patients with newly-diagnosed IBD, a flare or those being considered for biologics. We analysed cases of possible amoebic colitis after this change by reviewing IBD patients with a positive E. histolytica immunofluorescence antibody test (IFAT).

Methods

We conducted a retrospective electronic and case note review of patients with IBD and positive amoeba IFAT serology >1:80 from April 2019 through September 2019. We collected information including Crohn’s disease (CD), ulcerative colitis (UC), IBD treatment, histological findings, travel history, stool E. histolytica DNA polymerase chain reaction (PCR) and amoebic serology including IFAT and Cellulose Acetate Precipitin test (CAP). The histology of endoscopic biopsies for 16 of the IFAT positive patients was reviewed specifically for amoebic trophozoites.

Results

During the study period we identified 26 IFAT positive patients, excluded 3 patients that were felt to be non-IBD; 23 were included in the study. The median age was 37.8 (range 16–86); 43.5% were male. Four had a diagnosis of UC; 19 had CD. 12 were new IBD presentations. Seven patients had a relevant travel history (Jamaica, Thailand, Turkey, Italy, Greece, and Spain). Four did not have a travel history. Travel history was unknown for 12. Three patients were on biologics, one on biologics and thiopurines. Five were on thiopurines, three on thiopurines and steroids. Four were on steroids only, four on 5-ASAs. Three were on no treatment. Two out of 16 patients reviewed had amoebic trophozoites on endoscopic biopsy, unfortunately stool PCR was not sent on these two patients. Stool E. histolytica DNA PCR, was sent for 19 patients and was negative in those cases. All 24 patients were negative for CAP.

Conclusion

While IFAT is helpful in detecting past exposure it is only 75% sensitive for amoebic colitis. Even if IFAT and CAP are combined it is difficult to differentiate amoebic colitis from IBD. It is not clear if these cases represent past infections, early infections that precipitated an IBD flare, early infections that arose in the setting of immunosuppression, or false positive IFATs. The risk of infection in the immunosuppressed patient is high and the consequences of misdiagnosis are significant therefore a comprehensive screening method is merited; this may encompass IFAT ± CAP, stool E. histolytica DNA PCR, and possibly histological review.