title: The Netherlands Chlamydia cohort study (NECCST) protocol to assess the risk of late complications following Chlamydia trachomatis infection in women.
abstract: Chlamydia trachomatis (CT), the most common bacterial sexually transmitted infection (STI) among young women, can result in serious sequelae. Although the course of infection is often asymptomatic, CT may cause pelvic inflammatory disease (PID), leading to severe complications, such as prolonged time to pregnancy, ectopic pregnancy, and tubal factor subfertility. The risk of and risk factors for complications following CT-infection have not been assessed in a long-term prospective cohort study, the preferred design to define infections and complications adequately.
  
  
  
  In the Netherlands Chlamydia Cohort Study (NECCST), a cohort of women of reproductive age with and without a history of CT-infection is followed over a minimum of ten years to investigate (CT-related) reproductive tract complications. This study is a follow-up of the Chlamydia Screening Implementation (CSI) study, executed between 2008 and 2011 in the Netherlands. For NECCST, female CSI participants who consented to be approached for follow-up studies (n = 14,685) are invited, and prospectively followed until 2022. Four data collection moments are foreseen every two consecutive years. Questionnaire data and blood samples for CT-Immunoglobulin G (IgG) measurement are obtained as well as host DNA to determine specific genetic biomarkers related to susceptibility and severity of infection. CT-history will be based on CSI test outcomes, self-reported infections and CT-IgG presence. Information on (time to) pregnancies and the potential long-term complications (i.e. PID, ectopic pregnancy and (tubal factor) subfertility), will be acquired by questionnaires. Reported subfertility will be verified in medical registers. Occurrence of these late complications and prolonged time to pregnancy, as a proxy for reduced fertility due to a previous CT-infection, or other risk factors, will be investigated using longitudinal statistical procedures.
  
  
  
  In the proposed study, the occurrence of late complications following CT-infection and its risk factors will be assessed. Ultimately, provided reliable risk factors and/or markers can be identified for such late complications. This will contribute to the development of a prognostic tool to estimate the risk of CT-related complications at an early time point, enabling targeted prevention and care towards women at risk for late complications.
  
  
  
  Dutch Trial Register NTR-5597 . Retrospectively registered 14 February 2016.
authors.affiliation: Epidemiology and Surveillance Unit, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands. Bernice.Hoenderboom@rivm.nl.|Laboratory of Immunogenetics, Department Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands. Bernice.Hoenderboom@rivm.nl.
authors.forename: B M
authors.initials: BM
authors.lastname: Hoenderboom
authors.affiliation: Epidemiology and Surveillance Unit, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: A A M
authors.initials: AA
authors.lastname: van Oeffelen
authors.affiliation: Epidemiology and Surveillance Unit, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: B H B
authors.initials: BH
authors.lastname: van Benthem
authors.affiliation: Department of General Practice, Division Clinical Methods and Public Health, Academic Medical Center, Amsterdam, the Netherlands.|STI AIDS Netherlands (SOA AIDS Nederland), Amsterdam, The Netherlands.
authors.forename: J E A M
authors.initials: JE
authors.lastname: van Bergen
authors.affiliation: Department of Sexual Health, Infectious Diseases and Environmental Health, South Limburg Public Health Service (GGD South Limburg), Geleen, The Netherlands.|Department of Medical Microbiology, Care and Public Health Research Institute (CAPHRI), Maastricht University Medical Centre (MUMC+), Maastricht, The Netherlands.
authors.forename: N H T M
authors.initials: NH
authors.lastname: Dukers-Muijrers
authors.affiliation: Epidemiology and Surveillance Unit, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.|Department Infectious Disease Control, Municipal Public Health Service Rotterdam-Rijnmond (GGD Rotterdam), Rotterdam, The Netherlands.|Department of Public Health, Erasmus MC-University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: H M
authors.initials: HM
authors.lastname: Götz
authors.affiliation: Department of Sexual Health, Infectious Diseases and Environmental Health, South Limburg Public Health Service (GGD South Limburg), Geleen, The Netherlands.|Department of Medical Microbiology, Care and Public Health Research Institute (CAPHRI), Maastricht University Medical Centre (MUMC+), Maastricht, The Netherlands.
authors.forename: C J P A
authors.initials: CJ
authors.lastname: Hoebe
authors.affiliation: STI Outpatient Clinic, Public Health Service of Amsterdam (GGD Amsterdam), Amsterdam, The Netherlands.
authors.forename: A A
authors.initials: AA
authors.lastname: Hogewoning
authors.affiliation: Laboratory for Infectious Diseases and Perinatal Screening, Centre for Infectious Disease Control, National Institute of Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: F R M
authors.initials: FR
authors.lastname: van der Klis
authors.affiliation: Department Immune Mechanisms, Center for Infectious Disease control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: van Baarle
authors.affiliation: Department of Obstetrics and Gynaecology, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: J A
authors.initials: JA
authors.lastname: Land
authors.affiliation: Epidemiology and Surveillance Unit, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.|Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: M A B
authors.initials: MA
authors.lastname: van der Sande
authors.affiliation: STI Outpatient Clinic, Public Health Service of Amsterdam (GGD Amsterdam), Amsterdam, The Netherlands.
authors.forename: M G
authors.initials: MG
authors.lastname: van Veen
authors.affiliation: Department of Clinical Pharmacology and Toxicology, Maastricht University Medical Centre (MUMC+), Maastricht, The Netherlands.
authors.forename: F
authors.initials: F
authors.lastname: de Vries
authors.affiliation: Laboratory of Immunogenetics, Department Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands.|Institute for Public Health Genomics (IPHG), Department of Genetics and Cell Biology, Research School GROW (School for Oncology & Developmental Biology), Faculty of Health, Medicine & Life Sciences, University of Maastricht, Maastricht, The Netherlands.
authors.forename: S A
authors.initials: SA
authors.lastname: Morré
authors.affiliation: Epidemiology and Surveillance Unit, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: I V F
authors.initials: IV
authors.lastname: van den Broek
mesh_terms: D000328:Adult; D002690:Chlamydia Infections / Q000150:complications* / Q000453:epidemiology; D002692:Chlamydia trachomatis; D005260:Female; D006801:Humans; D009426:Netherlands; D000292:Pelvic Inflammatory Disease / Q000209:etiology; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000209:etiology; D011446:Prospective Studies; D012307:Risk Factors
keywords: Chlamydia trachomatis; Ectopic pregnancy; Host genetic biomarkers; Pelvic inflammatory disease; Serology; The Netherlands; Tubal factor subfertility