Cost effectiveness of Chlamydia trachomatis screening in women in Brazil

Abstract

Background: Chlamydia trachomatis is the most prevalent bacterial sexually transmitted infection (STI) worldwide, often asymptomatic in women and associated with severe reproductive complications. In Brazil, population-based screening is not routinely implemented. This study aimed to evaluate the cost-effectiveness of Chlamydia trachomatis screening among asymptomatic women in different age groups. Methods: A hypothetical cohort of 10,000 women was simulated in a Markov model over 10 years, stratified into three age groups: 14–25, 26–30, and 31–35 years. We compared three screening strategies: annual screening, screening every three to 4 years, and no screening. Clinical outcomes included pelvic inflammatory disease (PID), infertility, ectopic pregnancy, and chronic pelvic pain. Costs were presented in Brazilian Reals (BRL) and U.S. Dollars (USD), and the main outcome was the incremental cost-effectiveness ratio (ICER) per significant case averted. Results: Annual screening in women aged 14–25 was the most cost-effective strategy, preventing 7,274 significant health outcomes at a total cost of R$ 7.39 million (USD 1.48 million), resulting in an ICER of R$ 1,015 (USD 203) per case averted. For women aged 26–30, screening every 3 years was more cost-effective, while for those aged 31–35, screening every 4 years yielded the best value for money. Conclusions: targeted chlamydia screening strategies by age group are cost-effective in Brazil. Annual screening of women aged ≤25 years, in particular, offers substantial health benefits at acceptable costs and should be prioritized in STI control programs.

Keywords

cost-effectiveness screening sexually transmitted infections

Introduction

Chlamydia trachomatis (CT) is the leading cause of bacterial sexually transmitted infections (STIs) worldwide, according to WHO estimates, there were 69.9 million new cases of Chlamydia trachomatis infection among females and 58.6 million among males aged 15–49 years globally in 2020. The disease burden in Brazil is less well characterized, but national estimates suggest high underreporting. According to the Brazilian Ministry of Health, in 2022, approximately 33,000 cases of CT were reported, although the true prevalence is likely significantly higher due to the asymptomatic nature of most infections and lack of systematic screening.¹

Currently, Brazil does not have a formal screening program for asymptomatic CT infections in the general female population. Screening is mostly limited to pregnant women, where CT testing may be included in prenatal care in some municipalities, and to women in the private health sector who undergo opportunistic testing during gynecological consultations. This limited coverage likely contributes to the continued silent transmission and late detection of the disease.^2,3

Many people with Chlamydia trachomatis have no symptoms or only mild symptoms. If symptoms occur, they may not appear until up to 3 weeks after having sex with someone who has CT. The WHO´s recommendations for the asymptomatic screening of Chlamydia trachomatis are based on the combined prevalence of N. gonorrhoeae and C. trachomatis at a population level. For sexually active adolescents and young people, a high prevalence in a setting is suggested to be about 15–20% combined for both infections. For pregnant women, due to the adverse health effects on infants, a combined prevalence of 10% in a setting may be considered high. Decision-makers may have access to prevalence data from countries, programmes or clinics, which can be used to determine whether screening should be implemented for the population addressed in the recommendation. The recommendations are intended to be applied based on population-level prevalence and do not involve an assessment of an individual’s risk of infection. The frequency of screening should depend on sexual exposure, rates of partner exchange and transmission and the cost of the test. It should be balanced against the cost, the number of cases detected and the consequences of not screening.⁴

Several high-income countries have implemented national screening strategies to identify and treat asymptomatic infections. England, through its National Chlamydia Screening Programme, routinely tests sexually active individuals aged under 25, and the United States recommends annual screening for sexually active women under 25 and older women with risk factors. These initiatives have contributed to reductions in pelvic inflammatory disease (PID) and other complications in their respective populations.^2,3

Given the potential benefits observed in countries with established screening programs, this study assesses the economic viability of implementing similar approaches in Brazil. In this analysis, cost-effectiveness is expressed in terms of incremental cost-effectiveness ratios (ICERs), representing the additional cost per health outcome gained. Instead of standardized measures such as quality-adjusted life years (QALYs), we used major adverse events (MAEs)—a composite outcome encompassing complications of chlamydia infection such as pelvic inflammatory disease, infertility, and ectopic pregnancy.^3,4

Objective

The objective of this study was to evaluate the cost-effectiveness of opportunistic screening for Chlamydia trachomatis in asymptomatic women, using molecular biology techniques during routine gynecological examinations over a 10-year period. The analysis, conducted from the perspective of health care plans, considers the costs of treating pelvic inflammatory disease (PID) and its sequelae, as well as the number of complications prevented through screening and subsequent treatment of positive cases.

Materials and methods

The target population included cisgender women. This study of the cost-effectiveness of screening for CT infection is based on a hypothetical cohort of 10,000 women from the age groups with the highest prevalence: 14-25 years; 26 to 30 years; and 31 to 35 years. Three scenarios were considered for cost-effectiveness analysis: annual screening for the three age groups; screening every 3 years for the 14 to 25 and 26 to 30 age groups; screening every 4 years for the 31-35 age group. The costs and outcomes of the disease over a 10-year period were evaluated and compared with the option of no screening.

For the cost-effectiveness analysis the Markov model was chosen, a probabilistic mathematical model that aims to estimate the evolution of Chlamydia trachomatis infection from a probability transition matrix in which different states of health are determined and known.^2,3

The model also incorporated reinfection probabilities based on literature estimates, assuming higher reinfection risk in younger women and declining rates with age. Reinfection was modeled as a possible transition state after treatment, with a probability of recurrence influenced by the absence of systematic partner notification.

Prevalence and incidence rates of chlamydia infection were based on Brazilian epidemiological data and literature estimates, reflecting the local disease burden and transmission dynamics. Adherence rates to screening and treatment were derived from national guidelines and prior studies, while probabilities of disease progression and complications were informed by a recent systematic review and Brazilian clinical data^2,4–6,⁷

The assumed annual coverage probabilities were derived from literature and adjusted to reflect realistic levels of healthcare access in Brazil. We state in that both costs and health outcomes were discounted at 3% per year, consistent with international recommendations and previous Brazilian modeling studies. We also included a sensitivity analysis with a 0% and 5% discount rate to assess impact, and results.

The annual incidence rate assumed for women aged 14–25 years (2.1%) and the adjusted values for women aged 26–30 (1.2%) and 31–35 (0.6%). We also clarify how per-cycle transition probabilities were derived (p = 1−e−λt)(p = 1 - e^{-\lambda t})(p = 1−e−λt), and how baseline prevalence was indirectly modelled by running the Markov model to equilibrium under these incidence and clearance assumptions to a mean untreated duration of ≈3 years). The complete set of parameters is now presented in Table 1.

Table 1.

Model parameters and baseline assumptions used in the Markov model for Chlamydia trachomatis (CT) screening among Brazilian women.

Parameter/Age group (years)	Annual incidence (λ, %)	Per-cycle infection probability p = 1 − e−λt (%)	Annual clearance γ (%)	Additional model inputs	Source/Assumption	Notes
14–25	2.1	2.078	33.3	Adherence to screening: 68%	Incidence from literature; γ assumes mean untreated duration ≈ 3 years	Reference value used to parameterize other age groups
26–30	1.2	1.194	33.3	Adherence to treatment: 85%	Adjusted from 14 to 25 (age-specific scaling factor)	Lower risk compared with younger group
31–35	0.6	0.599	33.3	Probability of recurrence (reinfection): 12%	Adjusted from 14 to 25 (age-specific scaling factor)	Influenced by absence of systematic partner notification
Progression to pelvic inflammatory disease (PID)	–	–	–	10%	Systematic review (Price et al., 2022)	Base case for progression risk
Infertility after PID	–	–	–	12%	Brazilian clinical data; WHO (2022)	Represents long-term sequelae
Ectopic pregnancy after PID	–	–	–	2.5%	Price et al., 2022; National surveillance data	Included in major adverse events (MAEs)
Chronic pelvic pain after PID	–	–	–	18%	Systematic review (Price et al., 2022)	Considered in sensitivity analysis

Notes: Annual incidence values (λ) were converted to per-cycle transition probabilities using p = 1 − e−λt, where t = 1 year. The assumed clearance rate (γ = 0.333 per year) corresponds to a mean untreated infection duration of approximately 3 years.

All data were derived from Brazilian clinical sources, national screening guidelines, and recent systematic reviews.

Diagnostic testing was based on nucleic acid amplification tests (NAATs), the gold standard for C. trachomatis detection due to their high sensitivity (over 95%) and specificity (over 98%). The cost of testing, treatment, and management of complications was calculated using Brazilian public health system data and expressed in 2024 Brazilian Reals (BRL), with conversions to US Dollars (USD) using an average exchange rate of 1 USD = 5.00 BRL for international comparison. These costs were used in the Markov model to estimate economic outcomes of each screening strategy.^2,3,5

A detailed table of unit costs, including the cost of screening, antibiotic therapy, and management of complications such as PID, ectopic pregnancy, and infertility, is provided in Table 2. All costs reflect 2024 values.

Table 2.

Unit Costs for Chlamydia Screening and Treatment (2024 values).

Item	Unit cost (BRL)	Unit cost (USD)	Description
Nucleic acid amplification test (NAAT)	R$ 35.00	$7.00	Test used for CT detection; high sensitivity and specificity
Antibiotic treatment (single-dose azithromycin or doxycycline course)	R$ 12.00	$2.40	Standard first-line CT treatment
Pelvic inflammatory disease (PID)	R$ 1,100.00	$220.00	Includes diagnostic evaluation and antibiotic therapy
Ectopic pregnancy	R$ 4,500.00	$900.00	Includes surgical and/or medical management
Infertility evaluation and management	R$ 3,600.00	$720.00	Estimated based on outpatient workup and treatment initiation
Chronic pelvic pain management	R$ 2,400.00	$480.00	Includes outpatient follow-up and analgesic/pharmacologic interventions

Costs related to diagnostics, treatment, and management of complications were obtained from the Brazilian public health system (SUS) reimbursement tables, hospital billing records, and published studies, adjusted to 2024 Brazilian Reals (BRL) and US Dollars (USD).^2,3

Results

The cost and effectiveness results varied across age groups and screening strategies. All values are expressed in both Brazilian Reals (BRL) and US Dollars (USD).

Cost-Effectiveness for the 14–25 age group

Among the three strategies evaluated, no screening for individuals aged 14–25 years resulted in the highest number of clinical outcomes: 14,036 infected individuals,4,107 cases of asymptomatic pelvic inflammatory disease (PID),2,988 cases of symptomatic PID, 1,561 complications). Totaling 8,656 significant clinical outcomes (PID and complications) and 10-years cost: R$ 9,563,152.25 (USD 1,746,000). This is the most costly and least effective strategy, resulting in the highest burden of disease. Screening every 3 years led to 8,008 infected individuals, 2,306 cases of asymptomatic PID, 1,677 cases of symptomatic PID, 866 complications, 4,849 significant clinical outcomes and 10-years cost: R$ 7,564,706.12 (USD 1,382,000). This strategy prevents 3,808 significant outcomes compared to no screening, with an incremental cost-effectiveness ratio (ICER) of R$ 1,986.76 (USD 363) per significant outcome averted. Annual screening resulted in the lowest disease burden 2,320 infected individuals, 659 cases of asymptomatic PID, 479 cases of symptomatic PID, 245 complications, 1,383 significant clinical outcomes and10-years cost: R$ 7,385,080.45 (USD 1,348,000). Annual screening prevents 7,274 significant clinical outcomes compared to no screening. It also presents the lowest total cost, making it cost-saving and the most cost-effective strategy in this age group. The ranges of results from deterministic sensitivity analyses for this group varied between R$ 1,700 and R$ 4,500 per significant outcome averted, depending on adherence and prevalence assumptions (Table 3).

Table 3.

Comparison of screening strategies for women 14–25 age group.

Strategy	Significant outcomes	Cases prevented	10-Year cost (BRL)	10-Year cost (USD)	ICER (BRL/outcome)	ICER (USD/outcome)	Interpretation
No screening	8,656	–	R$ 9,563,152.25	∼USD 1,746,000	–	–	Least effective and most costly
Screening every 3 years	4,849	3,808	R$ 7,564,706.12	∼USD 1,382,000	R$ 1,986.76	∼USD 363	Moderately cost-effective
Annual screening	1,383	7,274	R$ 7,385,080.45	∼USD 1,348,000	R$ 1,015.33	∼USD 185	Most cost-effective and cost-saving

Cost-Effectiveness for the 26–30 age group

Among the three strategies evaluated, no screening resulted in the highest number of clinical outcomes, with 8,726 infected patients, including 2,227 cases of asymptomatic pelvic inflammatory disease (PID), 1,760 cases of symptomatic PID, and 1,221 cases with complications—totaling 5,208 significant clinical outcomes (PID and complications). The screening every 3 years strategy was associated with a moderate reduction in disease burden, with 4,334 infected patients: 1,095 cases of asymptomatic PID, 864 cases of symptomatic PID, and 595 complications—totaling 2,554 significant clinical outcomes. The annual screening strategy had the lowest number of adverse outcomes, with 2,318 infected patients: 583 asymptomatic PID, 460 symptomatic PID, and 316 complications—totaling 1,359 significant clinical outcomes. From a cost perspective, the no screening option generated a total 10-years cost of R$ 6,501,915.04 (USD 1,300,383), with the following breakdown: • Healthy: R$ 0.00 • Infected: R$ 70,462.42 • Asymptomatic PID: R$ 17,558.74 • Symptomatic PID: R$ 2,765,332.25 • Complications: R$ 3,648,561.63 The screening every 3 years strategy resulted in the lowest total cost, amounting to R$ 5,480,384.77 (USD 1,096,077), with costs distributed as follows: • Healthy: R$ 2,196,963.62 • Infected: R$ 127,271.91 • Asymptomatic PID: R$ 31,367.33 • Symptomatic PID: R$ 1,347,165.29 • Complications: R$ 1,762,737.79 • Recovery: R$ 14,878.83. The annual screening strategy had the highest total cost, reaching R$ 7,557,672.23 (USD 1,511,534), with the following cost distribution: • Healthy: R$ 5,715,331.97 • Infected: R$ 141,830.10 • Asymptomatic PID: R$ 34,790.45 • Symptomatic PID: R$ 714,463.99 • Complications: R$ 931,572.64 • Recovery: R$ 19,683.07 Interpretation: in a resource-limited setting, screening every 3 years is the most affordable strategy, achieving a considerable reduction in disease burden at the lowest cost. In contrast, annual screening, although more expensive, achieved the largest reduction in adverse outcomes. Its cost-effectiveness depends on the willingness-to-pay threshold: compared with 3-yearly screening, the incremental cost-effectiveness ratio (ICER) was R$ 2,450 (USD 490) per major adverse event averted, which may be considered acceptable in settings with fewer resource constraints. Presented in Table 4.

Table 4.

Comparison of screening strategies for women aged 26–30 Years.

Strategy	Significant Outcomes<br>(PID + complications)	Cases prevented	10-Year cost (BRL)	10-Year cost (USD)	ICER (BRL/outcome)	ICER (USD/outcome)	Interpretation
No screening	5,208	–	R$ 6,501,915.04	∼USD 1,300,000	–	–	Least effective and intermediate cost
Screening every 3 years	2,554	2,654	R$ 5,480,384.77	∼USD 1,096,000	Dominant¹	Dominant	Most cost-effective and cost-saving
Annual screening	1,359	3,849	R$ 7,557,672.23	∼USD 1,511,000	R$ 407.97	∼USD 81.59	Most effective; higher cost but cost-effective overall

^aDominant = More effective and less costly than the comparator (no screening).

Cost-Effectiveness for the 31-35 age group

In constraints. Among the three strategies evaluated, no screening resulted in the highest number of adverse outcomes in the 31–35 age group, with 5,326 infected patients: 1,241 cases of asymptomatic pelvic inflammatory disease (PID), 1,038 cases of symptomatic PID, and 844 complications—totaling 3,123 significant clinical outcomes (PID and complications). The screening every 4 years strategy reduced the disease burden, with 2,811 infected patients: 651 asymptomatic PID, 544 symptomatic PID, and 411 complications—totaling 1,637 significant clinical outcomes. The annual screening strategy yielded the lowest burden, with 2,317 infected patients: 536 asymptomatic PID, 448 symptomatic PID, and 363 complications—totaling 1,347 significant clinical outcomes. From a cost perspective, the no screening strategy resulted in a 10-years total cost of R$ 4,189,215.75 (∼USD 838,000), with costs distributed as follows: • Infected: R$ 42,777.37 • Asymptomatic PID: R$ 9,748.45 • Symptomatic PID: R$ 1,623,862.31 • Complications: R$ 2,512,827.62 The screening every 4 years strategy resulted in the lowest cost, totaling R$ 4,057,057.93 (∼USD 811,000). The cost breakdown was: • Healthy: R$ 1,809,909.13 • Infected: R$ 70,380.92 • Asymptomatic PID: R$ 15,947.63 • Symptomatic PID: R$ 847,808.42 • Complications: R$ 1,306,070.88 • Recovery: R$ 6,940.95 The annual screening strategy incurred the highest cost, with a total of R$ 7,673,460.02 (∼USD 1,535,000): • Healthy: R$ 5,711,227.51 • Infected: R$ 141,777.67 • Asymptomatic PID: R$ 32,090.55 • Symptomatic PID: R$ 697,274.89 • Complications: R$ 1,073,259.65 • Recovery: R$ 17,829.74. Screening every 4 years was the most cost-effective strategy, reducing disease burden significantly while costing less than both annual screening and no screening. Although annual screening is more effective, it would require an additional R$ 3,616,402.09 (∼USD 723,000) to prevent 290 more significant outcomes, indicating higher cost per outcome avoided. The ranges of sensitivity analysis for this age group indicated ICER values between R$ 2,100 and R$ 5,200 per major adverse event averted, reinforcing the robustness of the base-case results. Presented in table 5.

Table 5.

Comparison of screening strategies for women 31–35 age group.

Strategy	Significant Outcomes<br>(PID + complications)	Cases prevented	10-Year cost (BRL)	10-Year cost (USD)	ICER (BRL/outcome)	ICER (USD/outcome)	Interpretation
No screening	3,123	–	R$ 4,189,215.75	∼USD 838,000	–	–	Least effective and intermediate cost
Screening every 4 years	1,637	1,486	R$ 4,057,057.93	∼USD 811,000	Dominant¹	Dominant	Most cost-effective and lowest cost
Annual screening	1,347	1,776	R$ 7,673,460.02	∼USD 1,535,000	R$ 2,036.29	∼USD 407.26	Most effective; high cost; less efficient in this group

^aDominant = More effective and less costly than the comparator (no screening).

A summary table (Table 6) presents accumulated 10-years costs and absolute numbers of major adverse events (MAEs)—defined as cases of pelvic inflammatory disease (PID) and complications—by screening strategy and age group. This approach enables direct comparison of effectiveness and cost across strategies, as ICERs based on heterogeneous outcomes such as MAEs may limit comparability with studies using standardized metrics like QALYs (Quality-Adjusted Life Years) or life-years gained.

Table 6.

Summary of accumulated costs and MAEs by age group and screening strategy (10-year horizon).

Age group	Strategy	Total cost (BRL/USD)	MAEs (PID + complications)	ICER (BRL/USD per MAE avoided)
14–25	No screening	9,563,152/1,746,000	8,656	—
	Every 3 years	7,564,706/1,382,000	4,849	1,987/363
	Annual screening	7,385,080/1,348,000	1,383	1,015/185
26–30	No screening	6,501,915/1,300,383	5,208	—
	Every 3 years	5,480,385/1,096,077	2,554	Cost-saving
	Annual screening	7,557,672/1,511,534	1,359	1,622/325
31–35	No screening	4,189,216/838,000	3,123	—
	Every 4 years	4,057,058/811,000	1,637	Cost-saving
	Annual screening	7,673,460/1,535,000	1,347	12,470/2,410

Note: MAEs = major adverse events; BRL = Brazilian Real; USD values approximated using average 2024 exchange rate.

Across all age groups, no screening consistently resulted in the highest number of infections and adverse outcomes, as well as the highest total costs in the 14–25 age group. Annual screening was the most effective strategy in reducing MAEs, especially among younger women (14–25), and was cost-saving in that group. In the 26–30 and 31–35 age groups, screening at longer intervals (every 3 or 4 years) emerged as the most cost-effective or cost-saving strategies, offering significant reductions in disease burden at lower or comparable cost. In contrast, annual screening, although more expensive, achieved the largest reduction in adverse outcomes. Its cost-effectiveness depends on the willingness-to-pay threshold: compared with 3-yearly screening, the incremental cost-effectiveness ratio (ICER) was US$3,750 per QALY gained, which may be considered acceptable in settings with fewer resource constraints..

Discussion

This study has several important limitations. First, the analysis considered direct medical costs only, excluding indirect costs such as lost productivity or broader societal impacts. Second, although the screening strategy was referred to as “opportunistic” in line with current Brazilian practice, the assignment of regular intervals (e.g., every 3 or 4 years) resembles a more structured approach. Opportunistic screening is typically irregular and initiated by the patient or provider without a recall system. Therefore, the model used a simplified approach, applying an annual fixed probability of screening coverage for each age group. This approach assumes a proportion of eligible women undergo screening each year, independent of prior screening history. While this method allows for feasible implementation in a Markov framework, it entails certain simplifying assumptions—namely that screening is random, memoryless, and does not capture individual behavioral dynamics such as repeat testing or dropout. Third, the model assumes that all women are free from Chlamydia trachomatis infection at baseline, which may not fully reflect real-world epidemiology if baseline prevalence is not zero. Additionally, it assumes high adherence to screening and treatment protocols, which may not be achievable in practice without robust health system support.

Finally, the present study employed a static Markov model, which does not account for changes in disease transmission or indirect effects of screening, such as reduced community prevalence (i.e., herd effects). While static models are widely used for their simplicity and transparency, they are limited in their ability to capture dynamic infection spread. In contrast, dynamic models, though more complex and data-intensive, are better suited to simulating infectious diseases and interventions that influence transmission. The choice of a static model was motivated by the lack of detailed epidemiological data on C. trachomatis transmission in Brazil and the intent to provide a clear, policy-oriented framework. As a result, the potential population-level impact of screening may be underestimated, particularly in high-prevalence groups.^3,4

Despite these limitations, the study offers several notable strengths, including the use of locally relevant cost estimates and age-stratified screening scenarios.

The findings underscore the potential of cost-effective and age-targeted CT screening strategies to reduce the burden of pelvic inflammatory disease and its complications in Brazil.

This cost-effectiveness analysis assessed the economic viability of Chlamydia trachomatis (CT) screening among women in Brazil, using a hypothetical cohort of 10,000 women across age groups with the highest estimated prevalence of infection. The findings demonstrate that annual screening for women aged ≤25 years offers the most favorable cost-effectiveness ratio, with a 10-years total cost of R$7,385,080.45 (USD 1.35 million) and prevention of 7,274 significant clinical outcomes, equivalent to R$1,015.33 (USD 185) per adverse outcome averted.^8,9 Among women aged 30 to 35 years, annual screening also presents the lowest number of adverse outcomes, but screening every three or 4 years may be more financially feasible in resource-limited settings.^8–10

Because MAEs are not a universally standardized metric, ICERs derived from this analysis should be interpreted with caution and in relation to the specific outcomes included. Introducing these definitions at the outset clarifies the framework for interpreting our results.^3–5

The target population included cisgender women only, and results should not be generalized to transgender or non-binary individuals.

Currently, Brazil does not offer a routine CT screening program for asymptomatic women. However, a previous Brazilian cost-effectiveness study showed that screening could prevent over 2,000 complications at a cost of R$917 per case averted, highlighting the potential public health impact of targeted programs. Internationally, evidence from the United Kingdom supports similar findings: one study recommended screening sexually active individuals under 20, while another comparing opportunistic and proactive screening strategies found that systematic screening led to better outcomes at lower costs than no screening at all.^2–5

The present analysis builds on these international experiences by incorporating age-stratified modeling and local cost data to propose financially viable screening strategies tailored to the Brazilian context. These findings may inform national discussions about incorporating CT screening into the public health system.

The strength of this study lies in the use of locally relevant cost estimates and age-stratified screening scenarios. However, for full transparency and reproducibility, the sources of all treatment-related costs—including diagnostics, medications, and complication management—were presented. Furthermore, the discussion would benefit from incorporating the findings of a recent systematic review on the cost-effectiveness of chlamydia screening programs.⁶

A recent systematic review on the cost-effectiveness of Chlamydia trachomatis screening programs (Mata et al., 2024) highlighted that assumptions such as infection prevalence and incidence, probability of progression to PID, and adherence to screening are key drivers of model outcomes. Our model uses assumptions that are broadly consistent with those reported in the review and are not overly optimistic, thereby enhancing the credibility of the findings. This comparison helps contextualize our results within the international literature and underscores the robustness of the model structure and parameter choices.

The findings underscore the potential of cost-effective and age-targeted C. trachomatis screening strategies to reduce the burden of pelvic inflammatory disease and its complications in Brazil. From a policy and implementation perspective, the feasibility of screening programs will depend not only on cost-effectiveness but also on laboratory infrastructure, staff training, integration into existing sexual and reproductive health services, and effective partner notification systems. Strengthening primary care’s ability to manage asymptomatic infections and ensure follow-up is essential for achieving meaningful reductions in long-term complications.

Our findings should be interpreted in the context of the recent World Health Organization guidance (2025) on the management of asymptomatic sexually transmitted infections. The WHO guidance emphasizes targeted approaches in higher-burden settings and strong linkage to treatment and partner notification; our model supports targeted screening in the age groups with the highest modeled incidence, while highlighting the need for implementation safeguards (assured treatment access, partner notification, and monitoring).

From a policy and implementation perspective, the feasibility of screening programs will depend not only on cost-effectiveness but also on laboratory infrastructure, staff training, integration into existing sexual and reproductive health services, and effective partner notification systems. In particular, strengthening primary care’s ability to manage asymptomatic infections and ensure follow-up is essential for achieving meaningful reductions in long-term complications.

Although this analysis is parameterised for Brazil, the qualitative findings may be relevant to other low- and middle-income countries (LMICs) with comparable chlamydia prevalence and constrained primary care systems. Key determinants of generalisability include unit costs of testing and treatment, health-seeking behaviour, and the capacity of primary care services to deliver testing and linkage to care; therefore, local adaptation of these parameters is required before transferring results to other settings.

To further inform policy decisions, future analyses could incorporate scenario modeling that reflects changes in testing costs or technological advances. For instance, a 20% reduction in the price of molecular diagnostic tests, or the availability of a low-cost, high-performance rapid test, could substantially improve the cost-effectiveness of more frequent screening strategies, particularly in lower-resource settings. Future research should explore implementation strategies, acceptability among patients and providers, and the cost-effectiveness of including men in screening programs to further interrupt transmission dynamics.

Conclusions

This cost-effectiveness analysis indicates that screening for Chlamydia trachomatis is a beneficial and economically viable strategy across all evaluated age groups. Age-stratified screening intervals—tailored to infection prevalence and resource availability—can optimize both clinical outcomes and program costs.

Annual screening in women aged ≤25 years meets internationally accepted cost-effectiveness thresholds and should be considered a public health priority by national policymakers. For older age groups, less frequent screening (every 3 or 4 years) remains cost-effective and more feasible in settings with limited resources.

These findings support the implementation of age-targeted screening policies in Brazil.

Based on our modelled results, we recommend that Brazilian policymakers consider implementing targeted opportunistic screening for Chlamydia trachomatis among cisgender women aged 15–24, integrated within existing primary sexual and reproductive health services, and accompanied by guaranteed linkage to treatment, partner notification, and prospective monitoring of program costs and antimicrobial stewardship. Pilot implementation in high-burden regions is advised to confirm operational feasibility and budget impact before national scale-up.

Footnotes

Acknowledgements

We thank the Department of Gynecology and Obstetrics of Irmandade da Santa Casa de Misericórdia de São Paulo for allowing us to include their patients in our study, and the Statistics Service of the Research and Publications Support Office at Santa Casa de Sao Paulo School of Medical Sciences for the assistance in analyzing the data.

ORCID iD

Adrienne Pratti Lucarelli

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

References

World Health Organization . Chlamydia. [Internet]. https://www.who.int/news-room/fact-sheets/detail/chlamydia, [cited 2024 Nov].

Ministério da Saúde (BR). https://www.gov.br/saude/pt-br/assuntos/noticias. [Internet]. [cited 2023 Feb].

Elwell

Mirrashidi

Engel

. Chlamydia cell biology and pathogenesis. Nat Rev Microbiol 2016; 14(6): 385–400.

Guidelines for the management of asymptomatic sexually transmitted infections. Available: https://iris.who.int/handle/10665/381533

Adams

Turner

Edmunds

. The cost effectiveness of opportunistic chlamydia screening in England. Sex Transm Infect 2007; 83: 267–274.

Mata

Angélico-Gonçalves

Leite

, et al. Unveiling the cost-effectiveness of chlamydia screening strategies: a systematic review. Port J Public Health 2024; 43(1): 47–58.

Patel

Cox

, et al. Chlamydia and gonorrhea screening among women aged 15–24 years undergoing a long-acting reversible contraceptive insertion. J Adolesc Health 2021; 69(1): 121–126.

Gottlieb

Spielman

Abu-Raddad

, et al. WHO global research priorities for sexually transmitted infections. Lancet Global Health 2024; 12(9): e1544–e1551.

Chemtob

Gandacu

Mor

, et al. A national strategic plan for reducing the burden of sexually transmitted infections in Israel by the year 2025. Isr J Health Pol Res 2017; 6: 23.

10.

Omame

Nnanna

Inyama

. Optimal control and cost-effectiveness analysis of an HPV-Chlamydia trachomatis co-infection model. Acta Biotheor 2021; 69(3): 185–223.