Condition category
Infections and Infestations
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
Chlamydia is a common sexually transmitted infection. The current guidelines recommend testing again after a chlamydia infection, but the best timing is not known. The aim of this study is to find the best time to retest after chlamydia treatment.

Who can participate?
Heterosexual patients of the Amsterdam STI clinic with a chlamydia infection, aged 12 or older

What does the study involve?
After being diagnosed and treated, participants are randomly allocated to be offered a retest either 8, 16 or 26 weeks later. Participants can choose to do this at home and send a self-collected sample by mail, or at the clinic. The number and percentage of participants retested and chlamydia infection rates are assessed up to 35 weeks later.

What are the possible benefits and risks of participating?
The benefit for the participant is that chlamydia re-infections are diagnosed and treated. There are no risks involved in participation.

Where is the study run from?
Public Health Service (GGD) Amsterdam (Netherlands)

When is the study starting and how long is it expected to run for?
May 2012 to April 2017

Who is funding the study?
Public Health Service (GGD) Amsterdam (Netherlands)

Who is the main contact?
Prof. Henry de Vries

Trial website

Contact information



Primary contact

Prof Henry de Vries


Contact details

Public Health Service
Department of Infectious Diseases
Nieuwe Achtergracht 100

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

What is the optimal time to retest patients with a urogenital chlamydia infection? A randomized controlled trial


Study hypothesis

The trialists postulated that in heterosexual visitors of the STI clinic with a urogenital chlamydia infection, the proportion being retested would be lower with a later timing of retest, and that the proportion positive would be higher with a later timing of retest. If so, the trialists envisioned an optimum timing to offer a retest, which would provide the highest yield of diagnosed reinfections.

Ethics approval

The study was reviewed by the ethics committee of the Academic Medical Center, University of Amsterdam, Netherlands. The board exempted the study from a full review and written patient consent as it was a modification of current practice and did not apply to the Dutch law ‘Medical Research Involving Human Subjects Act (WMO)’.

Study design

Single-centre randomized controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

No participant information sheet available


Urogenital Chlamydia trachomatis infection


A single-centre randomized controlled trial among urogenital chlamydia nucleic acid amplification test positive heterosexual Amsterdam STI clinic clients. After treatment, patients were randomly assigned for retesting 8, 16 or 26 weeks later. Patients could choose to do this at home (and send a self-collected sample by mail), or at the clinic. Retest uptake and chlamydia positivity at follow-up were calculated.

Intervention type



Drug names

Primary outcome measure

1. The number and percentage of participants retested up to 35 weeks after inclusion
2. The proportion of participants who were CT positive, measured by nucleic acid amplification test, up to 35 weeks after inclusion

Secondary outcome measures

1. The number, percentage and chlamydia positivity proportion of participants who:
1.1. Returned more than 1 week before the assigned date
1.2. Returned at assigned date (this was defined as a visit in the period >1 week before, until 6 weeks after the assigned date)
1.3. Returned >6 weeks after the assigned date but no later than 35 weeks (8 months) after inclusion
1.4. Those who did not return within 35 weeks of inclusion

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Heterosexual patients of the Amsterdam STI clinic testing positive for urogenital chlamydia
2. Aged 12 years or older

Participant type


Age group




Target number of participants


Participant exclusion criteria

Does not meet inclusion criteria

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

Public Health Service (GGD) Amsterdam
STI outpatient clinic Department of Infectious Diseases Weesperplein 1
1018 WT

Sponsor information


Public Health Service

Sponsor details

Department of Infectious Diseases
Nieuwe Achtergracht 100
1018 WT

Sponsor type




Funder type


Funder name

Public Health Service (GGD) Amsterdam

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

The trialists have presented the preliminary results during two scientific meetings, in 2013 during the international society for STD Research (ISSTDR) meeting in Vienna, Austria, and in 2014 during the International Society for Human Chlamydia Infection (ISHCI) meeting in Monterrey, CA, USA. Currently they are submitting the definite results to a scientific peer reviewed journal.

IPD sharing plan
The datasets generated during and/or analysed during the current study are/will be available upon request from Prof. Henry de Vries.

Intention to publish date


Participant level data

Available on request

Basic results (scientific)

Publication list

2017 results in:

Publication citations

Additional files

Editorial Notes

14/11/2017: Publication reference added.