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
Abstract
BACKGROUND

Anal fistula is a pathological connection between the anal canal and perianal skin, which most commonly develops from an infected anal crypt. While the majority of anal fistulas are idiopathic, they are also associated with Crohn’s disease (CD) and other inflammatory conditions. The prevalence of anal fistula is estimated to be 1-2 per 10000 patients, but population-based studies on anal fistula epidemiology are limited and outdated.

AIM

To assess the prevalence of anal fistula and relevant comorbidities, with and without CD in the United Kingdom and Europe.

METHODS

A retrospective population-representative observational cohort study was performed in The Health Improvement Network (THIN), a United Kingdom primary care database. Mid-year point prevalence of anal fistula was calculated on the first of July for each year between 2014 and 2017. Estimates were calculated for anal fistula overall and by CD status and standardized to the United Kingdom and European population. Prevalence of relevant comorbidities including lymphogranuloma venereum, hidradenitis suppurativa, anal presentation of sexually transmitted diseases, diabetes mellitus, and radiation in the pelvic area was reported.

RESULTS

The United Kingdom-standardized overall point prevalence of anal fistula was 1.80 (95%CI: 1.65-1.94) per 10000 patients in 2017, while the Europe standardized estimate was 1.83 (95%CI: 1.68-1.98) per 10000 patients. Both these standardized point prevalence estimates ranged from 1.89 to 2.36 between 2014-2016. The United Kingdom-standardized point prevalence of anal fistula without CD was 1.35 (95%CI: 1.23-1.48) per 10000 patients, while the Europe-standardized estimate was 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. In 2017, 19% of anal fistula patients without CD and 13% of anal fistula patients with CD had at least one relevant comorbidity. These results show that anal fistulas are infrequent in the general population. 24.5% of prevalent anal fistulas are associated with CD, but other potentially etiological comorbidities are rare.

CONCLUSION

This real-world evidence study estimated the United Kingdom-standardized prevalence of anal fistula was 1.80 per 10000 patients in 2017. Approximately 25% of cases may be associated with CD, while other comorbidities are rare.

Keywords: Anal fistula, United Kingdom, Europe, Crohn’s disease, Comorbidities, Prevalence

Core tip: There is no recent data on the prevalence of anal fistula in Europe. The frequency of underlying risk conditions in anal fistula is also poorly understood. This real-world evidence study aimed to estimate United Kingdom and Europe-standardized prevalence of anal fistula, with and without Crohn’s disease (CD), and describe the prevalence of relevant comorbidities among patients with anal fistula. Data was derived from the The Health Improvement Network database. Overall, the United Kingdom and Europe- standardized prevalence of anal fistula were 1.80 and 1.83 per 10000 patients respectively in 2017 (1.89-2.36 in 2014-2016). Approximately 25% of anal fistula cases may be associated with CD, while other comorbidities are rare.