Article Text

Defining venous thromboembolism and measuring its incidence using Swedish health registries: a nationwide pregnancy cohort study
  1. Alyshah Abdul Sultan1,2,3,
  2. Joe West1,
  3. Olof Stephansson4,5,
  4. Matthew J Grainge1,
  5. Laila J Tata1,
  6. Kate M Fleming1,
  7. David Humes1,
  8. Jonas F Ludvigsson2,6
  1. 1Division of Epidemiology and Public Health, University of Nottingham, Nottingham, UK
  2. 2Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden
  3. 3Nottingham Digestive Diseases Biomedical Research Unit, University of Nottingham, Queens Medical Center, UK
  4. 4Department of Medicine, Clinical Epidemiology Unit, Karolinska Institutet, Stockholm, Sweden
  5. 5Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
  6. 6Department of Paediatrics, Örebro University Hospital, Örebro, Sweden
  1. Correspondence to Dr Alyshah Abdul Sultan; alyshah.sultan{at}hotmail.com

Abstract

Objective To accurately define venous thromboembolism (VTE) in the routinely collected Swedish health registers and quantify its incidence in and around pregnancy.

Study design Cohort study using data from the Swedish Medical Birth Registry (MBR) linked to the National Patient Registry (NPR) and the Swedish Prescribed Drug Register (PDR).

Setting Secondary care centres, Sweden.

Participant 509 198 women aged 15–44 years who had one or more pregnancies resulting in a live birth or stillbirth between 2005 and 2011.

Main outcome measure To estimate the incidence rate (IR) of VTE in and around pregnancy using various VTE definitions allowing direct comparison with other countries.

Results The rate of VTE varied based on the VTE definition. We found that 43% of cases first recorded as outpatient were not accompanied by anticoagulant prescriptions, whereas this proportion was much lower than those cases first recorded in the inpatient register (9%). Using our most inclusive VTE definition, we observed higher rates of VTE compared with previously published data using similar methodology. These reduced by 31% (IR=142/100 000 person-years; 95% CI 132 to 153) and 22% (IR=331/100 000 person-years; 95% CI 304 to 361) during the antepartum and postpartum periods, respectively, using a restrictive VTE definition that required anticoagulant prescriptions associated with diagnosis, which were more in line with the existing literature.

Conclusions We found that including VTE codes without treatment confirmation risks the inclusion of false-positive cases. When defining VTE using the NPR, anticoagulant prescription information should therefore be considered particularly for cases recorded in an outpatient setting.

  • OBSTETRICS
  • HAEMATOLOGY

This is an Open Access article 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/

View Full Text

Statistics from Altmetric.com

Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.