Retrospective Cohort Study
Copyright ©The Author(s) 2019. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Jul 26, 2019; 7(14): 1795-1804
Published online Jul 26, 2019. doi: 10.12998/wjcc.v7.i14.1795
Prevalence of anal fistula in the United Kingdom
Suvi RK Hokkanen, Naomi Boxall, Javaria Mona Khalid, Dimitri Bennett, Haridarshan Patel
Suvi RK Hokkanen, Naomi Boxall, Real World Evidence Solutions, IQVIA, London N19JY, United Kingdom
Javaria Mona Khalid, Evidence and Value Generation, Global Medical Affairs, Takeda Pharmaceuticals International Inc., London WC2B 4AE, United Kingdom
Dimitri Bennett, Department of Epidemiology, Takeda Pharmaceuticals International Inc., Cambridge, MA 02139, United States; Adjunct, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
Haridarshan Patel, Evidence and Value Generation, Global Medical Affairs, Takeda Pharmaceuticals International Inc., Deerfield, IL 6001, United States
Author contributions: Hokkanen SRK, Boxall N, Khalid JM, Bennett D and Patel H designed the research; Hokkanen SRK, Boxall N, Khalid JM, Bennett D and Patel H analyzed the data; Hokkanen SRK, Boxall N, Khalid JM, Bennett D and Patel H critically wrote and revised the manuscript for content.
Institutional review board statement: This study was reviewed and approved by the Scientific Review Committee.
Informed consent statement: Data from the THIN database is non-identifiable and utilizes an opt-out data scheme; patients who register for a general practitioner (GP) practice which contributes to THIN are informed that their records will be included in the dataset and are given the option to not participate. Where patients do opt-out, their data are not collected.
Conflict-of-interest statement: This study was funded by Takeda Pharmaceuticals International Inc. Dimitri Bennett and Haridarshan Patel are Takeda employees. Javaria Mona Khalid was a Takeda employee at the time of study conduct. Suvi RK Hokkanen and Naomi Boxall are IQVIA employees.
Data sharing statement: All data is presented in the current manuscript.
STROBE statement: Guidelines of the STROBE statement have been adopted.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Haridarshan Patel, PharmD, Pharmacist, Research Scientist, Evidence and Value Generation, Global Medical Affairs, Takeda Pharmaceuticals International Inc., 1 Takeda Pkwy, Deerfield, IL 6001, United States. hari.patel@takeda.com
Telephone: +1-224-5546500
Received: February 25, 2019
Peer-review started: February 26, 2019
First decision: March 28, 2019
Revised: May 8, 2019
Accepted: May 23, 2019
Article in press: May 23, 2019
Published online: July 26, 2019
ARTICLE HIGHLIGHTS
Research background

An anal (or perianal) fistula is defined as an external abnormal pathological connection between the anal canal and perianal skin. The majority of anal (or perianal) fistulas are idiopathic, associated with Crohn’s disease (CD) and, to a lesser extent, other inflammatory conditions.

Research motivation

There is no recent data on the prevalence of anal fistula in the United Kingdom or the Europe. The frequency of underlying risk conditions in anal fistula is also poorly understood.

Research objectives

This real-world evidence study aimed to estimate United Kingdom- and Europe-standardized prevalence of anal fistula, with and without CD. Additionally, the study aimed to describe the prevalence of relevant comorbidities among patients with anal fistula.

Research methods

A retrospective population-observational cohort study was performed using a United Kingdom primary care database. The prevalence of anal fistula by overall and CD status was calculated between 2014 and 2017. These estimates were standardized to the United Kingdom and Europe populations. Prevalence of relevant comorbidities was also reported.

Research results

Analysis estimated the United Kingdom- and Europe-standardized prevalence of anal fistula as 1.80 (95%CI: 1.65-1.94) and 1.83 (95%CI: 1.68-1.98) per 10000 patients, respectively in 2017. Between 2014-2016 the standardized point prevalence estimates ranged from 1.89 to 2.36. Analysis estimated the United Kingdom- and Europe-standardized prevalence of anal fistula without CD as 1.35 (95%CI: 1.23-1.48) and 1.39 (95%CI: 1.26-1.52) per 10000 patients. In contrast, the standardized point prevalence estimate of anal fistula with CD was lower for both United Kingdom and Europe (0.44; 95%CI United Kingdom: 0.37-0.52, 95%CI Europe: 0.37-0.51) per 10000 patients in 2017. Examining data from 2017 showed that 19% of anal fistula patients without CD and 13% of anal fistula patients with CD were associated with at least one relevant comorbidity. Data indicated that 24.5% of prevalent anal fistulas were associated with CD, whereas association with other potential comorbidities was uncommon.

Research conclusions

This real-world evidence study estimated the United Kingdom- and Europe-standardized prevalence of anal fistula were 1.80 and 1.83 per 10000 patients, respectively in 2017. Furthermore, almost 25% of cases appeared to be associated with CD but associations with other comorbidities seemed rare.

Research perspectives

This study presents new recent population-based data on the prevalence of anal fistula in the United Kingdom and Europe. As such, it highlights the significance of this devastating complication associated with CD and other relevant comorbidities. These prevalence estimates for anal fistula indicate a major need for novel therapeutic options for this population of patients.