CTstudy - The presence of Chlamydia trachomatis among the population in Belgium

Last updated on 14-12-2022 by Pierre Daubresse
Project duration:
May 1, 2019
May 1, 2020

In short

Chlamydia is the most registered sexually transmitted disease (STD) in Belgium, but the reported numbers do not necessarily reflect the actual distribution of Chlamydia in our population. Many people who have this infection do not show any symptoms, however they can still spread the sexually transmitted bacteria. That is why Sciensano wants to find out with this study how many people have an infection with Chlamydia and how this disease is spread across Belgium. The results of this study serve to guide prevention.

Participants in this study were chosen at random. They receive material to take a urine sample at home. The laboratory uses this urine to check whether the participant is infected. The urine test will also immediately detect the presence of Gonorrhea (another sexually transmitted bacterium). Participants can receive the test result on their request.

Information leaflet for portential participants

Project description

The exact prevalence of Chlamydia infections and the spread among the Belgian population are unknown. In Belgium, diagnostic tests for Chlamydia are mainly performed in specific target groups through opportunistic testing methods. As a result, the numbers reported by the laboratories do not necessarily reflect the actual distribution of Chlamydia trachomatis in the population in Belgium. Young women (20-24 years old) are thought to be overrepresented in the surveillance data based on laboratory data, while men and higher age groups may be underrepresented. Identifying the extent of Chlamydia infections and the spread among the population of Belgium helps prevention organisations to provide accurate, evidence-based information, and to focus prevention programs and possible screening on specific target groups.

This research has 3 objectives:

  1. estimate the prevalence of Chlamydia trachomatis infections in the population of Belgium
  2. identify risk factors associated with Chlamydia trachomatis infections in Belgium (age, gender, sexual behavior, socio-economic, geographical, …)
  3. estimate the prevalence of Neisseria gonorrhoeae infections in the population of Belgium, because the microbiological test for Chlamydia also detects Gonorrhea. If the result is positive, the participants are also informed.

The last objective, however, is limited by the rather limited sample size, which allows us to make decisions about prevalence at national level, but the accuracy of this estimate is limited.


Sciensano uses data from the national register to obtain a representative sample of the population in Belgium. The required sample size for Belgium is rounded to 2000 participants. The participants in this study can request their results.

Ethics committee

The research protocol was submitted for approval to the ethics committee of the University Hospital Antwerp and the Internal Review Board of the Institute for Tropical Medicine in Antwerp.


Sciensano is working on this project together with the Belgian statistical office (Statbel) and the Institute of Tropical Medicine.

Sciensano's project investigator(s):

Service(s) working on this project


Irith De Baetselier

Financial Source

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