Chlamydia Screening Programme Research Articles

Underlying reasons for primary care visits where chlamydia testing was performed in the United States, 2019-2022.

In the United States (US), most chlamydia cases are reported from non-STD clinics, and there is limited information focusing on the reasons for chlamydia testing in private settings. These analyses describe clinical visits to primary care providers where chlamydia testing was performed to help discern between screening and diagnostic testing for chlamydia. Using the largest primary care clinical registry in the US, the PRIME registry, chlamydia tests were identified using Current Procedural Terminology (CPT) procedure codes and categorized as either diagnostic testing for sexually transmitted infection (STI) related symptoms, screening for chlamydia, or "other", based on ICD-10 Evaluation and Management codes selected for visits. Of 120,013 clinical visits with chlamydia testing between January 1, 2019 and December 31, 2022, 70.4% were women; 20.6% were with STI-related symptoms, 59.9% were for screening, and 19.5% for "other" reasons. Of those 120,013 clinical visits with chlamydia testing, the logit model showed that patients were significantly more likely to have STI-related symptoms if they were female than male, non-Hispanic black than non-Hispanic white, aged 15-24 years than aged ≥45 years, and resided in the South than in the Northeast. It is important to know what proportion of chlamydial infections are identified through screening programs and to have this information stratified by demographics. The inclusion of lab results could further facilitate a better understanding of the impact of chlamydia screening programs on the identification and treatment of chlamydia in private office settings in the United States.

Chlamydia trachomatis: Management and screening

C hlamydia trachomatis is the most common sexually transmitted infection worldwide. In up to 50% of men and 70% of women, infection is asymptomatic or minimally symptomatic and can easily be missed. Untreated infection can cause significant morbidity including pelvic inflammatory disease and infertility. These harmful consequences occur predominantly in women. The UK National Chlamydia Screening Programme recommends opportunistic chlamydia screening for sexually active women who are less than 25 years old. This article provides a contemporary overview of chlamydia. Within this article, references to ‘women’ includes cisgender women and other people with a uterus or ovaries – including transgender men, non-binary people (assigned female at birth) and intersex people with a uterus or ovaries who have not had a hysterectomy or bilateral oophorectomy. ‘Men’ includes cisgender men as well as all other people with a penis and testes, including transgender women who have not had bilateral orchidectomy.

Effectiveness of Incentivized Peer Referral to Increase Enrollment in a Community-Based Chlamydia Screening and Treatment Study Among Young Black Men.

Young Black men are under-represented in sexual health services and research, a condition likely magnified during COVID-19 shutdowns due to disruption of STI screening and treatment services. We examined the effect of incentivized peer referral (IPR) increasing peer referral among young Black men in a community-based chlamydia screening program. Young Black men in New Orleans, LA, age 15-26years enrolled in a chlamydia screening program between 3/2018 and 5/2021 were included. Enrollees were provided with recruitment materials to distribute to peers. Starting July 28, 2020, enrollees were also offered a $5 incentive for each peer enrolled. Enrollment was compared before and after the incentivize peer referral program (IPR) was implemented using multiple time series analysis (MTSA). The percentage of men referred by a peer was higher during IPR compared to pre-IPR (45.7% vs. 19.7%, p < 0.001). After the COVID-19 shutdown was lifted, there were 2.007 more recruitments per week (p = 0.044, 95% CI (0.0515, 3.964)) for IPR, compared to pre-IPR. Overall, there was a trending increase in recruitments in the IPR era relative to the pre-IPR era (0.0174 recruitments/week, p = 0.285, 95% CI (- 0.0146, 0.0493)) with less recruitment decay during IPR compared to pre-IPR. IPR may be an effective means of engaging young Black men in community-based STI research and prevention programs, particularly when clinic access is limited. Clinicaltrials.gov identifier NCT03098329.

A framework for using real-time evaluative interview feedback for health promotion program and evaluation improvement: The Check It case study

Formative evaluation is a crucial strategy for health promotion program improvement. Early and ongoing formative evaluation can make a major impact on program outcomes; however, there are few frameworks that provide actual guidance on how programmatic or research teams can systematically perform this kind of important work. In this article we describe the use of an iterative real-time interview feedback framework we developed for Check It, a community-wide chlamydia screening and treatment program for young African American men in New Orleans, Louisiana. The framework considers the diverse and needed perspectives of multiple stakeholders, including participants, interviewers, transcribers, program staff, and lead researchers and/or administrators. Interviews were conducted with N = 15 Check It participants utilizing this approach. Employing the framework led to critical insights that resulted in several vital programmatic and evaluation improvements. Lessons learned, including strengths and challenges of utilizing the framework, are also shared so that this model can be replicated or adapted by program planning and evaluation professionals for other kinds of programs.

Therapeutic Options for Chlamydia trachomatis Infection: Present and Future.

Sexually transmitted infections (STIs), such as Chlamydia trachomatis (Ct) infection, have serious consequences for sexual and reproductive health worldwide. Ct is one of the most common sexually transmitted bacterial infections in the world, with approximately 129 million new cases per year. C. trachomatis is an obligate intracellular Gram-negative bacterium. The infection is usually asymptomatic, notwithstanding, it could also be associated with severe sequels and complications, such as chronic pain, infertility, and gynecologic cancers, and thus there is an urgent need to adequately treat these cases in a timely manner. Consequently, beyond its individual effects, the infection also impacts the economy of the countries where it is prevalent, generating a need to consider the hypothesis of implementing Chlamydia Screening Programs, a decision that, although it is expensive to execute, is a necessary investment that unequivocally will bring financial and social long-term advantages worldwide. To detect Ct infection, there are different methodologies available. Nucleic acid amplification tests, with their high sensitivity and specificity, are currently the first-line tests for the detection of Ct. When replaced by other detection methods, there are more false negative tests, leading to underreported cases and a subsequent underestimation of Ct infection's prevalence. Ct treatment is based on antibiotic prescription, which is highly associated with drug resistance. Therefore, currently, there have been efforts in line with the development of alternative strategies to effectively treat this infection, using a drug repurposing method, as well as a natural treatment approach. In addition, researchers have also made some progress in the Ct vaccine development over the years, despite the fact that it also necessitates more studies in order to finally establish a vaccination plan. In this review, we have focused on the therapeutic options for treating Ct infection, expert recommendations, and major difficulties, while also exploring the possible avenues through which to face this issue, with novel approaches beyond those proposed by the guidelines of Health Organizations.

The prevalence of Chlamydia infection in the United Kingdom (Uk): A critical review

The global overwhelming prevalence of Chlamydia trachomatis may not be unconnected to the asymptomatic nature of the infection. Over 50% of Chlamydia cases can only be detected through diagnosis. Chlamydia is the most diagnosed sexually transmitted infection in the United Kingdom and higher rates of infection are found in women than in men. Over 64% of diagnosed cases of Chlamydia in the UK are among young adults who are between the ages of 16-24 owing to their risky sexual behaviors. Chlamydia is most blame able for urethritis in both men and women. Although there is no currently known vaccine against Chlamydia trachomatis however, Chlamydial infection is preventable using condoms and treatable using antibiotics. Various programs and policies such as the National Chlamydia Screening Program NSCP have been inaugurated in the UK to encourage routine screening of all sexually active individuals and those who are particularly at risk. Although, the need to intensify more efforts towards effecting positive behavioral change among individuals with risky sexual behaviour. Also, more screening centres should be instituted at various locations easily accessible to individuals who are vulnerable to Chlamydial infection.

Chlamydia trachomatis as a Current Health Problem: Challenges and Opportunities.

Chlamydia is one of the most common sexually transmitted bacterial infections (STIs) worldwide. It is caused by Chlamydia trachomatis (CT), which is an obligate intracellular bacterium. In some cases, it can occur in coinfection with other parasites, increasing the pathologic potential of the infection. The treatment is based on antibiotic prescription; notwithstanding, the infection is mostly asymptomatic, which increases the risk of transmission. Therefore, some countries have implemented Chlamydia Screening Programs in order to detect undiagnosed infections. However, in Portugal, there is no CT screening plan within the National Health Service. There is no awareness in the general healthcare about the true magnitude of this issue because most of the methods used are not Nucleic Acid Amplification Technology-based and, therefore, lack sensitivity, resulting in underreporting infection cases. CT infections are also associated with possible long-term severe injuries. In detail, persistent infection triggers an inflammatory milieu and can be related to severe sequels, such as infertility. This infection could also trigger gynecologic tumors in women, evidencing the urgent need for cost-effective screening programs worldwide in order to detect and treat these individuals adequately. In this review, we have focused on the success of an implemented screening program that has been reported in the literature, the efforts made concerning the vaccine discovery, and what is known regarding CT infection. This review supports the need for further fundamental studies in this area in order to eradicate this infection and we also suggest the implementation of a Chlamydia Screening Program in Portugal.

Prevalence of Chlamydia trachomatis in the general population in Germany – a triangulation of data from two population-based health surveys and a laboratory sentinel system

BackgroundChlamydia trachomatis (chlamydia) is a common, frequently asymptomatic, sexually transmitted infection. It can result in severe sequelae, such as ectopic pregnancy and infertility. In Germany, chlamydia is not notifiable. An opportunistic screening program for women < 25 years was introduced in 2008. The aim of this research was to triangulate different data sources to describe the epidemiological situation of chlamydia in Germany and to investigate whether the current target group of the chlamydia screening program aligns with these findings.MethodsUrine specimens from participants from population-based health examination surveys of children (2014–17) and adults (2008–11) were tested for chlamydia, using nucleic acid amplification testing. These data were used to generate weighted chlamydia prevalence estimates by age group and sex. Data from a nationwide chlamydia laboratory sentinel system (2014–16) were used to calculate the positive proportion among individuals tested for chlamydia by age, sex and test reason.ResultsUsing data from the population-based surveys, we found a chlamydia prevalence estimate of 2.8% (95% confidence interval (CI) 1.0–7.5%) among all 15- to 17-year-old girls and of 9.6% (95% CI 0.0–23) among those reporting to be sexually active. In adult women, we found the highest prevalence among 18- to 24-year-olds (all: 2.3%; 95% CI 1.0–5.3%; sexually active: 3.1%; 95% CI 1.3–7.0%). In adult men, we found the highest prevalence among 25- to 29-year-olds (all: 3.5%; 95% CI 1.6–7.7%; sexually active: 3.3%; 95% CI 1.3–7.8%). Data from the chlamydia laboratory sentinel showed the highest positive proportion among those opportunistically screened in 19-year-old women (6.1%; 95%- CI 5.9–6.4%), among those screened due to pregnancy in 15-year-old girls (10%; 95% CI 8.5–12%), and among those tested due to symptoms or a positive partner in 19-year-old women (10%; 95% CI 9.8–11%) and 19-year-old men (24%; 95% CI 22–26%).ConclusionsChlamydia seems to mainly affect adolescents and young adults in Germany, with similar overall prevalence in men and women, but with slightly different age distributions. Women at highest risk of chlamydia are covered by the current screening program but given the on-going discussions in high-income countries on cost-effectiveness and benefit-to-harm ratio of these programs, the program-aim needs reconsideration.

An Audit Cycle Highlighting the Rate of Chlamydia Screening in a Forensic Child and Adolescent Mental Health Unit in Birmingham

AimsChlamydia, a sexually transmitted bacterial infection caused by Chlamydia Trachomatis can result in long-term complications for affected individuals. The National chlamydia screening programme recommends screening at-risk young persons, however for the vulnerable patients at the Forensic Child and Adolescent Mental Health Service (FCAMHS), there has been no audit to determine the completion rate. This audit aim to (1) Determine the demographics of young persons on admission (2) To determine the rate of chlamydia screening as well as the percentage of patients who qualified for a Chlamydia screening(3) To determine the rate of documentation for completed tests.MethodsThis was a retrospective study. The medical electronic records of patients who met the inclusion criteria was searched. All the three mixed-sex adolescent forensic wards (2 medium secure units and one low secure unit) at FCAMHS Ardenleigh, Birmingham were sampled.All patients that were on admission aged above 15 years of age were recruited.A total sample size of 19 was obtained for the initial audit and 12 for the re-audit.Data collectionData were collected by the author for the initial-audit and re-audit by searching the clinical progress notes, the investigation results and the physical health rethink forms. An excel software was used for analysis.ResultsDemographicsThere were 11 males (57.9%) and 8 females (42.1%) in the initial auditIn the re-audit, there were 7 males (58.3) and 5 females (41.7). Some of the patients were still on admission at the time of the re-audit, hence the percentages were calculated differently. The mean age and average length of admission was also calculated.Chlamydia screeningIn the initial audit, the percentage of patients tested for Chlamydia was 11.5%, even though 36.8% of patients met the criteria for Chlamydia screening. In the re-audit, 25.0% were tested, and 41.7% met the criteria for Chlamydia screening.Physical health (Rethink) formsThe physical health form was completed for majority of patients 73.7% in the initial audit although, this was not compatible with screening rates. Before the re-audit was concluded, the physical health forms were no longer in use.ConclusionThe audit highlighted an overall improvement in the rate of screening following recommendations from initial audit. The inclusion of Chlamydia screening in admission processes could be useful in improving sexual health.

The changing landscape of chlamydia control strategies

The National Chlamydia Screening Programme (NCSP) in England is changing its aim, to “focus on preventing adverse consequences of untreated chlamydia infection…rather than aiming to reduce prevalence”.1 In future, screening tests to detect asymptomatic Chlamydia trachomatis infection will no longer be offered to men younger than 25 years who attend primary care and community health services, but these tests will still be offered to women. The main reason behind this shift in strategy is that, more than 20 years after the start of the plans for the NCSP,2 there is still no clear evidence that widespread testing will reduce chlamydia transmission and have an impact on prevalence and complications.

What Do Diagnoses of Pelvic Inflammatory Disease in Specialist Sexual Health Services in England Tell Us About Chlamydia Control?

Pelvic inflammatory disease (PID) is an outcome measure for the evaluation of chlamydia screening programs. We explore PID diagnoses in specialist sexual health services (SSHSs) in England to inform the evaluation of the National Chlamydia Screening Programme, which was implemented nationally in 2008. We conducted descriptive analyses using data on diagnoses of PID-with and without Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (GC)-by age and year of birth, in SSHSs between 2009 and 2019 from the GUMCAD STI Surveillance System database. Rates were calculated per 100 000 females residing in England. CT screening activity peaked in 2010. The rates of all PID diagnoses decreased between 2009 and 2019 by 39%. CT-associated PID (CT-PID) declined by 58%, and nonspecific PID declined by 37%. GC-PID increased by 34%. CT-PID decreased across all age groups with the highest observed decline, 71%, in 15- to 19-year-olds. A dose-response relationship was observed between CT-PID rates and screening, with rates lowest in those with the greatest exposure to screening. There was a marked decline in diagnoses of CT-PID, and nonspecific PID, at SSHSs after the introduction of widespread chlamydia screening, whereas GC-PID diagnoses increased. This ecological trend was broadly consistent with what we would have expected to see if widespread screening reduced the incidence of chlamydia-associated PID (and of nonspecific PID), as has been observed in randomized controlled trials of screening.

A Systematic Review of New Approaches to Sexually Transmitted Infection Screening Framed in the Capability, Opportunity, Motivation, and Behavior Model of Implementation Science.

Chlamydia and gonorrhea are 2 of the most common bacterial sexually transmitted infections (STIs) worldwide. Rising chlamydia and gonorrhea rates along with increased closing of STI clinics has led many to seek STI testing in clinical settings such as urgent cares and walk-in clinics. However, with competing priorities, providing effective and efficient STI care can be difficult in these settings. This has left a growing need for the implementation of novel STI screening programs in other clinical settings. This review summarizes previous studies that have evaluated the clinical implementation of chlamydia and gonorrhea screening programs in these settings. Literature from January 2015 to February 2020 regarding the implementation or evaluation of STI screening programs in clinical settings was reviewed. Constructs from the Capability, Opportunity, Motivation, and Behavior model were used to organize results, as this model can aid in identifying specific strategies for behavior/process change interventions. We found that multiple STI screening programs have been implemented and evaluated in 5 different countries and multiple health care facilities including sexual health clinics, urgent cares, walk-in clinics, and university health clinics. When implementing new STI screening programs, sample-first, test-and-go services and molecular point-of-care (POC) testing approaches were found to be effective in increasing screening and reducing costs and time to treatment. At the health care systems level, these programs can help reduce STI screening costs and generate additional revenue for clinics. At the provider level, clear communication and guidance can help clinical and administrative staff in adopting new screening programs. Finally, at the patient level, new programs can reduce time to treatment and travel costs in visiting clinics multiple times for testing and treatment services.

Exploration of introducing a chlamydia screening programme to the Democratic People's Republic of Korea

Chlamydia trachomatis is a common STI that is often asymptomatic, and can only be diagnosed through a screening test. Despite acute infection being asymtpoamtic, long term consequences of untreated CT infection can lead to infertility in men and women, increased risk of ectopic preganancy, and the economic burden of the long-term impacts far outweigh the cost of testing and treatment. Despite this, there is currently no concentrated CT screening programme in the DPRK, a region that is indicated to have high STI rates, including CT. Taking into account prevalency, the geopolitical situation of the DPRK, and the cost per positive test, this paper explores whether or not a CT screening programme would be cost-effective in the DPRK.

Management of chlamydia and gonorrhoea infections diagnosed in primary care using a centralised nurse-led telephone-based service: mixed methods evaluation

BackgroundUp to 18% of genital Chlamydia infections and 9% of Gonorrhoea infections in England are diagnosed in Primary Care. Evidence suggests that a substantial proportion of these cases are not managed appropriately in line with national guidelines. With the increase in sexually transmitted infections and the emergence of antimicrobial resistance, their timely and appropriate treatment is a priority. We investigated feasibility and acceptability of extending the National Chlamydia Screening Programme’s centralised, nurse-led, telephone management (NLTM) as an option for management of all cases of chlamydia and gonorrhoea diagnosed in Primary Care.MethodsRandomised feasibility trial in 11 practices in Bristol with nested qualitative study. In intervention practices patients and health care providers (HCPs) had the option of choosing NLTM or usual care for all patients tested for Chlamydia and Gonorrhoea. In control practices patients received usual care.ResultsOne thousand one hundred fifty-four Chlamydia/gonorrhoea tests took place during the 6-month study, with a chlamydia positivity rate of 2.6% and gonorrhoea positivity rate of 0.8%. The NLTM managed 335 patients. Interviews were conducted with sixteen HCPs (11 GPs, 5 nurses) and 12 patients (8 female). HCPs were positive about the NLTM, welcomed the partner notification service, though requested more timely feedback on the management of their patients. Explaining the NLTM to patients didn’t negatively impact on consultations. Patients found the NLTM acceptable, more convenient and provided greater anonymity than usual care. Patients appreciated getting a text message regarding a negative result and valued talking to a sexual health specialist about positive results.ConclusionExtension of this established NLTM intervention to a greater proportion of patients was both feasible and acceptable to both patients and HCP, could provide a better service for patients, whilst decreasing primacy care workload. The study provides evidence to support the wider implementation of this NLTM approach to managing chlamydia and gonorrhoea diagnosed in primary care.

Mathematical modeling study of school-based chlamydia screening: potential impact on chlamydia prevalence in intervention schools and surrounding communities

BackgroundChlamydia screening in high schools offers a way to reach adolescents outside of a traditional clinic setting. Using transmission dynamic modeling, we examined the potential impact of high-school-based chlamydia screening programs on the burden of infection within intervention schools and surrounding communities, under varying epidemiological and programmatic conditions.MethodsA chlamydia transmission model was calibrated to epidemiological data from three different settings. Philadelphia and Chicago are two high-burden cities with existing school-based screening programs. Rural Iowa does not have an existing program but represents a low-burden setting. We modeled the effects of the two existing programs to analyze the potential influence of program coverage and student participation. All three settings were used to examine a broader set of hypothetical programs with varying coverage levels and time trends in participation.ResultsIn the modeled Philadelphia program, prevalence among the intervention schools’ sexually active 15–18 years old population was 4.34% (95% credible interval 3.75–4.71%)after 12 program years compared to 5.03% (4.39–5.43%) in absence of the program. In the modeled Chicago program, prevalence was estimated as 5.97% (2.60–7.88%) after 4 program years compared to 7.00% (3.08–9.29%) without the program. In the broader hypothetical scenarios including both high-burden and low-burden settings, impact of school-based screening programs was greater in absolute terms in the higher-prevalence settings, and benefits in the community were approximately proportional to population coverage of intervention schools. Most benefits were garnered if the student participation did not decline over time.ConclusionsSustained high student participation in school-based screening programs and broad coverage of schools within a target community are likely needed to maximize program benefits in terms of reduced burden of chlamydia in the adolescent population.

Who is coming back for more chlamydia testing within non-specialist health services and where do they go? England, 2013–2016

ObjectivesTo investigate patient demographics and venue type preferences within community settings associated with re-attendance for chlamydia testing. Study designData used for this analysis were obtained from the English National Chlamydia Screening Programme (NCSP) which focuses on prevention, control and treatment of chlamydia in sexually active under-25 year olds. A greater understanding of how young adults attend services helps to inform commissioners regarding where to focus resources within community settings. MethodsData from the Chlamydia surveillance system (CTAD) were used to count patient attendances at non-specialist sexual health services (SHSs) among 15–24-year-olds and monitor re-attendance for chlamydia testing within and between community services between 6 and 18 months of their first visit. ResultsFrom January 2013 to December 2016, 866,847 young people underwent 1,041,245 tests for chlamydia. Re-attendance for chlamydia testing was 20.1% (174,398/866,847). Re-attendance rate was 28.5% after a positive test and 19.5% after a negative test. For re-attenders, 64.2% used the same venue type for both visits. General practice (GP) and sexual and reproductive health services (SRH) were the most commonly re-attended services (31.0% and 30.6% respectively). ConclusionsOnly one in five re-attended for chlamydia testing. Re-attendance was associated with having a positive result, accessibility and convenience. Patients are likely to return for testing to services they know. This should be considered by commissioners implementing new re-attendance guidance based on the NCSP.

Cost-Effectiveness of a School-Based Chlamydia Screening Program, Duval County, FL.

During the 2015-2016 school year, the Florida Department of Health in Duval County hosted Teen Health Centers (TeenHC) at five high schools of Jacksonville providing HIV/STD screening and pregnancy testing. The purpose of this study was to assess the cost-effectiveness of the TeenHC chlamydia screening program and determine at what student participation level, the program can be cost-effective. We assessed the costs and effectiveness of the chlamydia screening program compared with "no TeenHC". Cost-effectiveness was measured as cost per quality-adjusted life years (QALY) gained. At a program cost of US$61,001 and 3% participation rate, the cost/QALY gained was $124,328 in the base-case analysis and $81,014-$264,271 in 95% of the simulation trials, all greater than the frequently citied $50,000/QALY benchmark. The cost/QALY gained could be <$50,000/QALY if student participation rate was >7%. The TeenHC chlamydia screening has the potential to be cost-effective. Future program efforts should focus on improving student participation.

Economic evaluation of the cost of different methods of retesting chlamydia positive individuals in England

ObjectivesThe National Chlamydia Screening Programme (NCSP) in England opportunistically screens eligible individuals for chlamydia infection. Retesting is recommended three3 months after treatment following a positive test result, but no guidance...

Has Chlamydia trachomatis prevalence in young women in England, Scotland and Wales changed? Evidence from national probability surveys.

We evaluate the utility of the National Surveys of Attitudes and Sexual Lifestyles (Natsal) undertaken in 2000 and 2010, before and after the introduction of the National Chlamydia Screening Programme, as an evidence source for estimating the change in prevalence of Chlamydia trachomatis (CT) in England, Scotland and Wales. Both the 2000 and 2010 surveys tested urine samples for CT by Nucleic Acid Amplification Tests (NAATs). We examined the sources of uncertainty in estimates of CT prevalence change, including sample size and adjustments for test sensitivity and specificity, survey non-response and informative non-response. In 2000, the unadjusted CT prevalence was 4.22% in women aged 18-24 years; in 2010, CT prevalence was 3.92%, a non-significant absolute difference of 0.30 percentage points (95% credible interval -2.8 to 2.0). In addition to uncertainty due to small sample size, estimates were sensitive to specificity, survey non-response or informative non-response, such that plausible changes in any one of these would be enough to either reverse or double any likely change in prevalence. Alternative ways of monitoring changes in CT incidence and prevalence over time are discussed.

Study protocol of the iMPaCT project: a longitudinal cohort study assessing psychological determinants, sexual behaviour and chlamydia (re)infections in heterosexual STI clinic visitors

BackgroundChlamydia trachomatis (chlamydia), the most commonly reported sexually transmitted infection (STI) in the Netherlands, can lead to severe reproductive complications. Reasons for the sustained chlamydia prevalence in young individuals, even in countries with chlamydia screening programs, might be the asymptomatic nature of chlamydia infections, and high reinfection rates after treatment. When individuals are unaware of their infection, preventive behaviour or health-care seeking behaviour mostly depends on psychological determinants, such as risk perception. Furthermore, behaviour change after a diagnosis might be vital to reduce reinfection rates. This makes the incorporation of psychological determinants and behaviour change in mathematical models estimating the impact of interventions on chlamydia transmission especially important. Therefore, quantitative real-life data to inform these models is needed.MethodsA longitudinal cohort study will be conducted to explore the link between psychological and behavioural determinants and chlamydia (re)infection among heterosexual STI clinic visitors aged 18–24 years. Participants will be recruited at the STI clinics of the public health services of Amsterdam, Hollands Noorden, Kennemerland, and Twente. Participants are enrolled for a year, and questionnaires are administrated at four time points: baseline (before an STI consultation), three-week, six-month and at one-year follow-up. To be able to link psychological and behavioural determinants to (re)infections, participants will be tested for chlamydia at enrolment and at six-month follow-up. Data from the longitudinal cohort study will be used to develop mathematical models for curable STI incorporating these determinants to be able to better estimate the impact of interventions.DiscussionThis study will provide insights into the link between psychological and behavioural determinants, including short-term and long-term changes after diagnosis, and chlamydia (re)infections. Our mathematical model, informed by data from the longitudinal cohort study, will be able to estimate the impact of interventions on chlamydia prevalence, and identify and prioritise successful interventions for the future. These interventions could be implemented at STI clinics tailored to psychological and behavioural characteristics of individuals.Trial registrationDutch Trial Register NTR-6307. Retrospectively registered 11-nov-2016.