Costs and effects of chlamydial screening: dynamic versus static modeling

Costs, Health Benefits, and Cost-Effectiveness of Chlamydia Screening and Partner Notification in the United States, 2000-2019: A Mathematical Modeling Analysis

BACKGROUND

Chlamydia remains a significant public health problem that contributes to adverse reproductive health outcomes. In the United States, sexually active women 24 years and younger are recommended to receive annual screening for chlamydia. In this study, we evaluated the impact of estimated current levels of screening and partner notification (PN), and the impact of screening based on guidelines on chlamydia associated sequelae, quality adjusted life years (QALYs) lost and costs.

METHODS

We conducted a cost-effectiveness analysis of chlamydia screening, using a published calibrated pair formation transmission model that estimated trends in chlamydia screening coverage in the United States from 2000 to 2015 consistent with epidemiological data. We used probability trees to translate chlamydial infection outcomes into estimated numbers of chlamydia-associated sequelae, QALYs lost, and health care services costs (in 2020 US dollars). We evaluated the costs and population health benefits of screening and PN in the United States for 2000 to 2015, as compared with no screening and no PN. We also estimated the additional benefits that could be achieved by increasing screening coverage to the levels indicated by the policy recommendations for 2016 to 2019, compared with screening coverage achieved by 2015.

RESULTS

Screening and PN from 2000 to 2015 were estimated to have averted 1.3 million (95% uncertainty interval [UI] 490,000-2.3 million) cases of pelvic inflammatory disease, 430,000 (95% UI, 160,000-760,000) cases of chronic pelvic pain, 300,000 (95% UI, 104,000-570,000) cases of tubal factor infertility, and 140,000 (95% UI, 47,000-260,000) cases of ectopic pregnancy in women. We estimated that chlamydia screening and PN cost $9700 per QALY gained compared with no screening and no PN. We estimated the full realization of chlamydia screening guidelines for 2016 to 2019 to cost $30,000 per QALY gained, compared with a scenario in which chlamydia screening coverage was maintained at 2015 levels.

DISCUSSION

Chlamydia screening and PN as implemented in the United States from 2000 through 2015 has substantially improved population health and provided good value for money when considering associated health care services costs. Further population health gains are attainable by increasing screening further, at reasonable cost per QALY gained.

Using an agent-based sexual-network model to analyze the impact of mitigation efforts for controlling chlamydia

Chlamydia trachomatis (Ct) is the most reported sexually transmitted infection in the United States, with a major cause of infertility, pelvic inflammatory disease, and ectopic pregnancy among women. Despite decades of screening women for Ct, rates increase among young African Americans (AA). We create and analyze a heterosexual agent-based network model to help understand the spread of Ct. We calibrate the model parameters to agree with survey data showing Ct prevalence of 12% of the women and 10% of the men in the 15-25 year-old AA in New Orleans, Louisiana. Our model accounts for both long-term and casual partnerships. The network captures the assortative mixing of individuals by preserving the joint-degree distributions observed in the data. We compare the effectiveness of intervention strategies based on randomly screening men, notifying partners of infected people, which includes partner treatment, partner screening, and rescreening for infection. We compare the difference between treating partners of an infected person both with and without testing them. We observe that although increased Ct screening, rescreening, and treating most of the partners of infected people will reduce the prevalence, these mitigations alone are not sufficient to control the epidemic. The current practice is to treat the partners of an infected individual without first testing them for infection. The model predicts that if a sufficient number of the partners of all infected people are tested and treated, then there is a threshold condition where the epidemic can be mitigated. This threshold results from the expanded treatment network created by treating an individual's infected partners' partners. Although these conclusions can help design future Ct mitigation studies, we caution the reader that these conclusions are for the mathematical model, not the real world, and are contingent on the validity of the model assumptions.

The natural history of Chlamydia trachomatis infection in women: a multi-parameter evidence synthesis

BACKGROUND AND OBJECTIVES

The evidence base supporting the National Chlamydia Screening Programme, initiated in 2003, has been questioned repeatedly, with little consensus on modelling assumptions, parameter values or evidence sources to be used in cost-effectiveness analyses. The purpose of this project was to assemble all available evidence on the prevalence and incidence of Chlamydia trachomatis (CT) in the UK and its sequelae, pelvic inflammatory disease (PID), ectopic pregnancy (EP) and tubal factor infertility (TFI) to review the evidence base in its entirety, assess its consistency and, if possible, arrive at a coherent set of estimates consistent with all the evidence.

METHODS

Evidence was identified using 'high-yield' strategies. Bayesian Multi-Parameter Evidence Synthesis models were constructed for separate subparts of the clinical and population epidemiology of CT. Where possible, different types of data sources were statistically combined to derive coherent estimates. Where evidence was inconsistent, evidence sources were re-interpreted and new estimates derived on a post-hoc basis.

RESULTS

An internally coherent set of estimates was generated, consistent with a multifaceted evidence base, fertility surveys and routine UK statistics on PID and EP. Among the key findings were that the risk of PID (symptomatic or asymptomatic) following an untreated CT infection is 17.1% [95% credible interval (CrI) 6% to 29%] and the risk of salpingitis is 7.3% (95% CrI 2.2% to 14.0%). In women aged 16-24 years, screened at annual intervals, at best, 61% (95% CrI 55% to 67%) of CT-related PID and 22% (95% CrI 7% to 43%) of all PID could be directly prevented. For women aged 16-44 years, the proportions of PID, EP and TFI that are attributable to CT are estimated to be 20% (95% CrI 6% to 38%), 4.9% (95% CrI 1.2% to 12%) and 29% (95% CrI 9% to 56%), respectively. The prevalence of TFI in the UK in women at the end of their reproductive lives is 1.1%: this is consistent with all PID carrying a relatively high risk of reproductive damage, whether diagnosed or not. Every 1000 CT infections in women aged 16-44 years, on average, gives rise to approximately 171 episodes of PID and 73 of salpingitis, 2.0 EPs and 5.1 women with TFI at age 44 years.

CONCLUSIONS AND RESEARCH RECOMMENDATIONS

The study establishes a set of interpretations of the major studies and study designs, under which a coherent set of estimates can be generated. CT is a significant cause of PID and TFI. CT screening is of benefit to the individual, but detection and treatment of incident infection may be more beneficial. Women with lower abdominal pain need better advice on when to seek early medical attention to avoid risk of reproductive damage. The study provides new insights into the reproductive risks of PID and the role of CT. Further research is required on the proportions of PID, EP and TFI attributable to CT to confirm predictions made in this report, and to improve the precision of key estimates. The cost-effectiveness of screening should be re-evaluated using the findings of this report.

FUNDING

The Medical Research Council grant G0801947.

Cost-effectiveness analysis of Chlamydia trachomatis screening in Dutch pregnant women

Chlamydia trachomatis infections during pregnancy may have serious consequences for women and their offspring. Chlamydial infections are largely asymptomatic. Hence, prevention is based on screening. The objective of this study was to estimate the cost-effectiveness of C. trachomatis screening during pregnancy. We used a health-economic decision analysis model, which included potential health outcomes of C. trachomatis infection for women, partners and infants, and premature delivery. We estimated the cost-effectiveness from a societal perspective using recent prevalence data from a population-based prospective cohort study among pregnant women in the Netherlands. We calculated the averted costs by linking health outcomes with health care costs and productivity losses. Cost-effectiveness was expressed as net costs per major outcome prevented and was estimated in base-case analysis, sensitivity, and scenario analysis. In the base-case analysis, the costs to detect 1000 pregnant women with C. trachomatis were estimated at €527,900. Prevention of adverse health outcomes averted €626,800 in medical costs, resulting in net cost savings. Sensitivity analysis showed that net cost savings remained with test costs up to €22 (test price €19) for a broad range of variation in underlying assumptions. Scenario analysis showed even more cost savings with targeted screening for women less than 30 years of age or with first pregnancies only. Antenatal screening for C. trachomatis is a cost-saving intervention when testing all pregnant women in the Netherlands. Savings increase even further when testing women younger than 30 years of age or with pregnancies only.

Vaccine epidemiology: A review

This review article outlines the key concepts in vaccine epidemiology, such as basic reproductive numbers, force of infection, vaccine efficacy and effectiveness, vaccine failure, herd immunity, herd effect, epidemiological shift, disease modeling, and describes the application of this knowledge both at program levels and in the practice by family physicians, epidemiologists, and pediatricians. A case has been made for increased knowledge and understanding of vaccine epidemiology among key stakeholders including policy makers, immunization program managers, public health experts, pediatricians, family physicians, and other experts/individuals involved in immunization service delivery. It has been argued that knowledge of vaccine epidemiology which is likely to benefit the society through contributions to the informed decision-making and improving vaccination coverage in the low and middle income countries (LMICs). The article ends with suggestions for the provision of systematic training and learning platforms in vaccine epidemiology to save millions of preventable deaths and improve health outcomes through life-course.

Chlamydia sequelae cost estimates used in current economic evaluations: does one-size-fit-all?

BACKGROUND

Current evidence suggests that chlamydia screening programmes can be cost-effective, conditional on assumptions within mathematical models. We explored differences in cost estimates used in published economic evaluations of chlamydia screening from seven countries (four papers each from UK and the Netherlands, two each from Sweden and Australia, and one each from Ireland, Canada and Denmark).

METHODS

From these studies, we extracted management cost estimates for seven major chlamydia sequelae. In order to compare the influence of different sequelae considered in each paper and their corresponding management costs on the total cost per case of untreated chlamydia, we applied reported unit sequelae management costs considered in each paper to a set of untreated infection to sequela progression probabilities. All costs were adjusted to 2013/2014 Great British Pound (GBP) values.

RESULTS

Sequelae management costs ranged from £171 to £3635 (pelvic inflammatory disease); £953 to £3615 (ectopic pregnancy); £546 to £6752 (tubal factor infertility); £159 to £3341 (chronic pelvic pain); £22 to £1008 (epididymitis); £11 to £1459 (neonatal conjunctivitis) and £433 to £3992 (neonatal pneumonia). Total cost of sequelae per case of untreated chlamydia ranged from £37 to £412.

CONCLUSIONS

There was substantial variation in cost per case of chlamydia sequelae used in published chlamydia screening economic evaluations, which likely arose from different assumptions about disease management pathways and the country perspectives taken. In light of this, when interpreting these studies, the reader should be satisfied that the cost estimates used sufficiently reflect the perspective taken and current disease management for their respective context.

Do different decision-analytic modeling approaches produce different results? A systematic review of cross-validation studies

When choosing a modeling approach for health economic evaluation, certain criteria are often considered (e.g., population resolution, interactivity, time advancement mechanism, resource constraints). However, whether these criteria and their associated modeling approach impacts results remain poorly understood. A systematic review was conducted to identify cross-validation studies (i.e., modeling a problem using different approaches with the same body of evidence) to offer insight on this topic. With respect to population resolution, reviewed studies suggested that both aggregate- and individual-level models will generate comparable results, although a practical trade-off exists between validity and feasibility. In terms of interactivity, infectious-disease models consistently showed that, depending on the assumptions regarding probability of disease exposure, dynamic and static models may produce dissimilar results with opposing policy recommendations. Empirical evidence on the remaining criteria is limited. Greater discussion will therefore be necessary to promote a deeper understanding of the benefits and limits to each modeling approach.

Heterogeneity in risk of pelvic inflammatory diseases after chlamydia infection: a population-based study in Manitoba, Canada

BACKGROUND

The association between chlamydia infection and pelvic inflammatory disease (PID) is a key parameter for models evaluating the impact of chlamydia control programs. We quantified this association using a retrospective population-based cohort.

METHODS

We used administrative health data sets to construct a retrospective population-based cohort of women and girls aged 12-24 years who were resident in Manitoba, Canada, between 1992 and 1996. We performed survival analysis on a subcohort of individuals who were tested for chlamydia to estimate the risk of PID diagnosed in a primary care, outpatient, or inpatient setting after ≥ 1 positive chlamydia test.

RESULTS

A total of 73 883 individuals contributed 625 621 person years of follow-up. Those with a diagnosis of chlamydia had an increased risk of PID over their reproductive lifetime compared with those who tested negative (adjusted hazard ratio [AHR], 1.55; 95% confidence interval [CI], 1.43-1.70). This risk increased with each subsequent infection: the AHR was 1.17 for first reinfection (95% CI, 1.06-1.30) and 1.35 for the second (95% CI, 1.04-1.75). The increased risk of PID from reinfection was highest in younger individuals (AHR, 4.55 (95% CI, 3.59-5.78) in individuals aged 12-15 years at the time of their second reinfection, compared with individuals older than 30 years).

CONCLUSIONS

There is heterogeneity in the risk of PID after a chlamydia infection. Describing the progression to PID in mathematical models as an average rate may be an oversimplification; more accurate estimates of the cost-effectiveness of screening may be obtained by using an individual-based measure of risk. Health inequalities may be reduced by targeting health promotion interventions at sexually active girls younger than 16 years and those with a history of chlamydia.

A review of Human Immunodeficiency Virus (HIV) rapid testing

BACKGROUND

In Canada, it is estimated that 71,300 persons were living with HIV at the end of 2011. Approximately 25% (14,500 to 21,500) of prevalent cases were unaware of their HIV infection. Expanded use of HIV rapid tests may increase the detection of undiagnosed infections, enable earlier treatment and support services and prevent the onward transmission of HIV.

OBJECTIVE

To examine patient acceptability, impact (defined as receipt of test results and linkage to care) and cost-effectiveness of HIV rapid tests.

METHODS

A search was conducted for systematic reviews on HIV rapid testing, with studies from both developed and developing countries, published in English and between 2000 and 2013. The Assessment of Multiple Systematic Review (AMSTAR) tool was used to assess the included systematic reviews for methodological quality. Results were summarized narratively for each of the outcomes.

RESULTS

Eight systematic reviews were included. Acceptability of HIV rapid tests was generally high in medical settings (69% to 98%) especially among pregnant women and youth attending emergency rooms but was lower in non-medical settings (14% to 46%). The percentage of people who obtained their test results was variable. It was high (83% to 93%) in emergency rooms but was low in a rapid care setting with regular business hours (27%). Impact on linkage to care was limited. Only one systematic review examined cost-effectiveness of rapid testing and concluded that HIV rapid tests were cost-effective in comparison to traditional methods; however, results were all based on static models.

CONCLUSION

Overall, HIV rapid tests demonstrated generally high acceptability, variability in receiving test results and limited impact on linkage to care. While these findings suggest that HIV rapid tests may be useful, further research is needed to confirm in whom, when and where they are best used and how to ensure better linkage to care.

How robust are the natural history parameters used in chlamydia transmission dynamic models? A systematic review

Transmission dynamic models linked to economic analyses often form part of the decision making process when introducing new chlamydia screening interventions. Outputs from these transmission dynamic models can vary depending on the values of the parameters used to describe the infection. Therefore these values can have an important influence on policy and resource allocation. The risk of progression from infection to pelvic inflammatory disease has been extensively studied but the parameters which govern the transmission dynamics are frequently neglected. We conducted a systematic review of transmission dynamic models linked to economic analyses of chlamydia screening interventions to critically assess the source and variability of the proportion of infections that are asymptomatic, the duration of infection and the transmission probability. We identified nine relevant studies in Pubmed, Embase and the Cochrane database. We found that there is a wide variation in their natural history parameters, including an absolute difference in the proportion of asymptomatic infections of 25% in women and 75% in men, a six-fold difference in the duration of asymptomatic infection and a four-fold difference in the per act transmission probability. We consider that much of this variation can be explained by a lack of consensus in the literature. We found that a significant proportion of parameter values were referenced back to the early chlamydia literature, before the introduction of nucleic acid modes of diagnosis and the widespread testing of asymptomatic individuals. In conclusion, authors should use high quality contemporary evidence to inform their parameter values, clearly document their assumptions and make appropriate use of sensitivity analysis. This will help to make models more transparent and increase their utility to policy makers.

Dynamic transmission modeling: a report of the ISPOR-SMDM Modeling Good Research Practices Task Force Working Group-5

The transmissible nature of communicable diseases is what sets them apart from other diseases modeled by health economists. The probability of a susceptible individual becoming infected at any one point in time (the force of infection) is related to the number of infectious individuals in the population, will change over time, and will feed back into the future force of infection. These nonlinear interactions produce transmission dynamics that require specific consideration when modeling an intervention that has an impact on the transmission of a pathogen. Best practices for designing and building these models are set out in this paper.

Dynamic transmission modeling: a report of the ISPOR-SMDM Modeling Good Research Practices Task Force--5

The transmissible nature of communicable diseases is what sets them apart from other diseases modeled by health economists. The probability of a susceptible individual becoming infected at any one point in time (the force of infection) is related to the number of infectious individuals in the population, will change over time, and will feed back into the future force of infection. These nonlinear interactions produce transmission dynamics that require specific consideration when modeling an intervention that has an impact on the transmission of a pathogen. Best practices for designing and building these models are set out in this article.

Managing health care decisions and improvement through simulation modeling

Simulation modeling is a way to test changes in a computerized environment to give ideas for improvements before implementation. This article reviews research literature on simulation modeling as support for health care decision making. The aim is to investigate the experience and potential value of such decision support and quality of articles retrieved. A literature search was conducted, and the selection criteria yielded 59 articles derived from diverse applications and methods. Most met the stated research-quality criteria. This review identified how simulation can facilitate decision making and that it may induce learning. Furthermore, simulation offers immediate feedback about proposed changes, allows analysis of scenarios, and promotes communication on building a shared system view and understanding of how a complex system works. However, only 14 of the 59 articles reported on implementation experiences, including how decision making was supported. On the basis of these articles, we proposed steps essential for the success of simulation projects, not just in the computer, but also in clinical reality. We also presented a novel concept combining simulation modeling with the established plan-do-study-act cycle for improvement. Future scientific inquiries concerning implementation, impact, and the value for health care management are needed to realize the full potential of simulation modeling.

Dynamic versus static models in cost-effectiveness analyses of anti-viral drug therapy to mitigate an influenza pandemic

Conventional (static) models used in health economics implicitly assume that the probability of disease exposure is constant over time and unaffected by interventions. For transmissible infectious diseases this is not realistic and another class of models is required, so-called dynamic models. This study aims to examine the differences between one dynamic and one static model, estimating the effects of therapeutic treatment with antiviral (AV) drugs during an influenza pandemic in the Netherlands. Specifically, we focus on the sensitivity of the cost-effectiveness ratios to model choice, to the assumed drug coverage, and to the value of several epidemiological factors. Therapeutic use of AV-drugs is cost-effective compared with non-intervention, irrespective of which model approach is chosen. The findings further show that: (1) the cost-effectiveness ratio according to the static model is insensitive to the size of a pandemic, whereas the ratio according to the dynamic model increases with the size of a pandemic; (2) according to the dynamic model, the cost per infection and the life-years gained per treatment are not constant but depend on the proportion of cases that are treated; and (3) the age-specific clinical attack rates affect the sensitivity of cost-effectiveness ratio to model choice.

Evaluation design of a systematic, selective, internet-based, Chlamydia screening implementation in the Netherlands, 2008-2010: implications of first results for the analysis

BACKGROUND

A selective, systematic, Internet-based, Chlamydia Screening Implementation for 16 to 29-year-old residents started in three regions in the Netherlands in April 2008: in the cities of Amsterdam and Rotterdam and a more rural region, South Limburg. This paper describes the evaluation design and discusses the implications of the findings from the first screening round for the analysis. The evaluation aims to determine the effects of screening on the population prevalence of Chlamydia trachomatis after multiple screening rounds.

METHODS

A phased implementation or 'stepped wedge design' was applied by grouping neighbourhoods (hereafter: clusters) into three random, risk-stratified blocks (A, B and C) to allow for impact analyses over time and comparison of prevalences before and after one or two screening rounds. Repeated simulation of pre- and postscreening Chlamydia prevalences was used to predict the minimum detectable decline in prevalence. Real participation and positivity rates per region, block, and risk stratum (high, medium, and low community risk) from the 1st year of screening were used to substantiate predictions.

RESULTS

The results of the 1st year show an overall participation rate of 16% of 261,025 invitees and a positivity rate of 4.2%, with significant differences between regions and blocks. Prediction by simulation methods adjusted with the first-round results indicate that the effect of screening (minimal detectable difference in prevalence) may reach significance levels only if at least a 15% decrease in the Chlamydia positivity rate in the cities and a 25% decrease in the rural region after screening can be reached, and pre- and postscreening differences between blocks need to be larger.

CONCLUSIONS

With the current participation rates, the minimal detectable decline of Chlamydia prevalence may reach our defined significance levels at the regional level after the second screening round, but will probably not be significant between blocks of the stepped wedge design. Evaluation will also include other aspects and prediction models to obtain rational advice about future Chlamydia screening in the Netherlands.

Development and Evaluation of GIS-Based Chlamydia Trachomatis Intervention Policy in Illinois

Chlamydia trachomatis is the most prevalent infectious disease in the United States. Complications include pelvic inflammatory disease (PID), ectopic pregnancy, and infertility. The cost of PID in 1998 was estimated at greater than $1.9 billion. Screening intervention strategies are often consumed by those at low risk. The objective of this study is the development of a more cost-effective intervention strategy by employing Geographic Information Systems and Census Bureau demographic data in selected Local Health Departments in Illinois. Case studies of intervention activities at the state and local level were performed. An evaluability assessment model of current inputs, processes and outcomes was created. A proposed model utilizing additional state inputs was developed and tested. Interventions were evaluated for effectiveness in reducing the incidence of Chlamydia trachomatis. Societal cost effectiveness analysis was also performed. The proposed model was tested in 2006. Results indicate that only minimal changes in annual incidence are required for GIS-augmented interventions to be cost-effective.

Conclusions on (cost-)effectiveness of pertussis booster vaccination strategies highly dependent on selections made in evidence review

This letter reacts on a paper recently published in this journal, reviewing the effectiveness and (cost-)effectiveness of pertussis booster vaccination strategies. We argue that a different selection of (cost-)effectiveness data could validly be made than the one presented in the review as being considered most robust. In particular, we explicitly present an alternative set of (cost-)effectiveness data.

Epidemiology of Chlamydia trachomatis infection in women and the cost-effectiveness of screening

BACKGROUND

The majority of Chlamydia trachomatis infections in women are asymptomatic, but may give rise to pelvic inflammatory disease (PID) and tubal infertility. Screening programmes aim at reducing morbidity in individuals by early detection and treatment, and at decreasing the overall prevalence of infection in the population. A number of modelling studies have tried to calculate the threshold prevalence of chlamydia lower genital tract infection above which screening becomes cost-effective. There is considerable debate over the exact complication rates after chlamydia infections, and more precise estimates of PID and tubal infertility are needed, for instance to be inserted in economic models.

METHODS

With reference to key studies and systematic reviews, an overview is provided focusing on the epidemiology of chlamydia infection and the risk-estimates of its late complications.

RESULTS

In the literature, the generally assumed risk of developing PID after lower genital tract chlamydia infection varies considerably, and is up to 30%. For developing tubal infertility after PID the risks are 10-20%. This implies that the risk of test-positive women of developing tubal infertility would range between 0.1 and 6%. We included chlamydia IgG antibody testing in a model and estimated a risk of tubal infertility up to 4.6%.

CONCLUSION

The risk of developing late complications after chlamydia lower genital tract infection appears low. High quality RCTs dealing with the transition from cervicitis to infertility are needed to broaden the evidence. In screening programmes, chlamydia antibody testing, as an intermediate marker for potential adverse sequelae, might enable more precise estimates.

Age-based programs for vaccination against HPV

BACKGROUND

The risk of infection with human papillomavirus (HPV) increases with age. Answering the question of which age groups are appropriate to target for catch-up vaccination with the newly licensed quadrivalent HPV vaccine (types 6/11/16/18) will be important for developing vaccine policy recommendations.

OBJECTIVES

To assess the value of varying female HPV vaccination strategies by specific age groups of a catch-up program in the United States.

METHODS

The authors used previously published mathematical population dynamic model and cost-utility analysis to evaluate the public health impact and cost-effectiveness of alternative quadrivalent HPV (6/11/16/18) vaccination strategies. The model simulates heterosexual transmission of HPV infection and occurrence of cervical intraepithelial neoplasia (CIN), cervical cancer, and external genital warts in an age-structured population stratified by sex and sexual activity groups. The cost-utility analysis estimates the cost of vaccination, screening, diagnosis, and treatment of HPV diseases, and quality-adjusted survival.

RESULTS

Compared with the current screening practices, vaccinating girls and women ages 12 to 24 years was the most effective strategy, reducing the number of HPV6/11/16/18-related genital warts, CIN grades 2 and 3, and cervical cancer cases among women in the next 25 years by 3,049,285, 1,399,935, and 30,021; respectively. The incremental cost-effectiveness ratio of this strategy when compared with vaccinating girls and women ages 12 to 19 years was $10,986 per quality-adjusted life-year gained. CONCLUSION;: Relative to other commonly accepted health-care programs, vaccinating girls and women ages 12 to 24 years appears cost-effective.

Assessment of the routine, occupation-based gonorrhea and syphilis screening program in Moscow, Russia: an analysis of sexually transmitted infection prevalence and cost-effectiveness

OBJECTIVES

In the Russian Federation, large sectors of the population regularly undergo mandatory occupational screening for sexually transmitted infections (STIs). Objectives of our study were to determine the prevalence of syphilis and gonorrhea in the screened occupational groups in Moscow and to conduct a cost-effectiveness evaluation of the occupational screening program.

STUDY DESIGN

Serum samples from 4 main occupational groups (food handlers and other food industry workers, market salespersons, education and health care providers, and hotel and other public utility workers) were tested for syphilis and gonorrhea. We conducted a cost-effectiveness analysis (in 2003 rubles) of the screening program using decision analysis models.

RESULTS

In the total sample of 1000 study participants, overall prevalence for syphilis was 1.2% with the highest rate in market salespersons (4.4%) and for gonorrhea 0.3%. The incremental cost per case of STI treated was 8409 rubles ($252) for syphilis screening (compared with no screening) with higher incremental costs associated with expanding the program to include gonorrhea screening. The relatively low STI prevalence in the screened groups and the poor performance of the diagnostic tests used were important factors in the estimated cost-effectiveness of occupation-based screening.

CONCLUSIONS

Modifications to occupation-based screening, including an increased focus on higher risk population and the adoption of more current diagnostic technologies, could help to use prevention resources more effectively.

Formulas for estimating the costs averted by sexually transmitted infection (STI) prevention programs in the United States

Background

Sexually transmitted infection (STI) prevention programs can mitigate the health and economic burden of STIs. A tool to estimate the economic benefits of STI programs could prove useful to STI program personnel.

Methods

We developed formulas that can be applied to estimate the direct medical costs and indirect costs (lost productivity) averted by STI programs in the United States. Costs and probabilities for these formulas were based primarily on published studies.

Results

We present a series of formulas that can be used to estimate the economic benefits of STI prevention (in 2006 US dollars), using data routinely collected by STI programs. For example, the averted sequelae costs associated with treating women for chlamydia is given as (C_w)(0.16)(0.925)(0.70)($1,995), where C_w is the number of infected women treated for chlamydia, 0.16 is the absolute reduction in the probability of pelvic inflammatory disease (PID) as a result of treatment, 0.925 is an adjustment factor to prevent double-counting of PID averted in women with both chlamydia and gonorrhea, 0.70 is an adjustment factor to account for the possibility of re-infection, and $1,995 is the average cost per case of PID, based on published sources.

Conclusion

The formulas developed in this study can be a useful tool for STI program personnel to generate evidence-based estimates of the economic impact of their program and can facilitate the assessment of the cost-effectiveness of their activities.

Costs and health consequences of chlamydia management strategies among pregnant women in sub-Saharan Africa

OBJECTIVES

Chlamydia is the most common bacterial sexually transmitted infection worldwide and a major cause of morbidity-particularly among women and neonates. We compared costs and health consequences of using point-of-care (POC) tests with current syndromic management among antenatal care attendees in sub-Saharan Africa. We also compared erythromycin with azithromycin treatment and universal with age-based chlamydia management.

METHODS

A decision analytical model was developed to compare diagnostic and treatment strategies, using Botswana as a case. Model input was based upon (1) a study of pregnant women in Botswana, (2) literature reviews and (3) expert opinion. We expressed the study outcome in terms of costs (US$), cases cured, magnitude of overtreatment and successful partner treatment.

RESULTS

Azithromycin was less costly and more effective than erythromycin. Compared with syndromic management, testing all attendees on their first visit with a 75% sensitive POC test increased the number of cases cured from 1500 to 3500 in a population of 100,000 women, at a cost of US$38 per additional case cured. This cost was lower in high-prevalence populations or if testing was restricted to teenagers. The specific POC tests provided the advantage of substantial reductions in overtreatment with antibiotics and improved partner management.

CONCLUSIONS

Using POC tests to diagnose chlamydia during antenatal care in sub-Saharan Africa entails greater health benefits than syndromic management does-and at acceptable costs-especially when restricted to younger women. Changes in diagnostic strategy and treatment regimens may improve people's health and even reduce healthcare budgets.

The cost effectiveness of opportunistic chlamydia screening in England

BACKGROUND/AIM

The National Chlamydia Screening Programme (NCSP) is being implemented in England. This study aims to estimate the cost effectiveness of (a) the NCSP strategy (annual screening offer to men and women aged under 25 years) and (b) alternative screening strategies.

METHODS

A stochastic, individual based, dynamic sexual network model was combined with a cost effectiveness model to estimate the complications and associated costs of chlamydial infection. The model was constructed and parameterised from the perspective of the National Health Service (NHS) (England), including the direct costs of infection, complications and screening. Unit costs were derived from standard data sources and published studies. The average and incremental cost effectiveness ratio (cost per major outcome averted or quality adjusted life year (QALY) gained) of chlamydia screening strategies targeting women and/or men of different age groups was estimated. Sensitivity analyses were done to explore model uncertainty.

RESULTS

All screening strategies modelled are likely to cost the NHS money and improve health. If pelvic inflammatory disease (PID) progression is less than 10% then screening at any level is unlikely to be cost effective. However, if PID progression is 10% or higher the NCSP strategy compared to no screening appears to be cost effective. The incremental cost effectiveness analysis suggests that screening men and women aged under 20 years is the most beneficial strategy that falls below accepted thresholds. There is a high degree of uncertainty in the findings.

CONCLUSIONS

Offering an annual screening test to men and women aged under 20 years may be the most cost effective strategy (that is, under accepted thresholds) if PID progression is 10% or higher.

Prevalence of Chlamydia trachomatis in a public colposcopy clinic population

BACKGROUND

Chlamydia trachomatis is a major public health issue, with notifications of this sexually transmitted disease continuing to rise in Australia. Women attending colposcopy clinics are referred for treatment of cervical abnormalities often associated with human papilloma virus (HPV) infection. There is evidence that women who have acquired one sexually transmitted infection, such as HPV, are at higher risk of acquiring another. Women attending colposcopy clinics may therefore be at risk of undiagnosed infection with C. trachomatis.

AIM

To determine the prevalence of C. trachomatis in women attending a public metropolitan colposcopy clinic in Victoria.

METHODS

A cross-sectional study was performed. Institutional ethics committee approval and informed consent were obtained. Consecutive women attending the colposcopy clinic completed a questionnaire and had a swab collected from the endocervix for analysis by polymerase chain reaction for C. trachomatis. Positive screens were treated in accordance with best practice. Data were analysed with Minitab Version 2004 (Minitab Inc, State College, PA, USA).

RESULTS

Of 581 women approached to participate in the trial, consent was obtained from 568 women (98%) and final outcome data was available on 560 women (99%). The overall rate of chlamydial infection was 2.1% (95% CI 1.5-2.7%). However, in women aged 25 years or less the rate was 5.8% (95% CI 3.8-7.8%) and in women over 25 years it was only 0.9% (95% CI 0.4-1.4%). Apart from age, no other demographic factor was significantly associated with chlamydial infection.

CONCLUSION

Although the prevalence of chlamydial infection in the colposcopy clinic population as a whole does not warrant a policy for routine screening, screening directed at women aged 25 years or less would gain the greatest yields in terms of cost efficacy. Such a policy should be implemented as standard practice.

Cost effectiveness of home based population screening for Chlamydia trachomatis in the UK: economic evaluation of chlamydia screening studies (ClaSS) project

OBJECTIVE

To investigate the cost effectiveness of screening for Chlamydia trachomatis compared with a policy of no organised screening in the United Kingdom.

DESIGN

Economic evaluation using a transmission dynamic mathematical model.

SETTING

Central and southwest England.

PARTICIPANTS

Hypothetical population of 50,000 men and women, in which all those aged 16-24 years were invited to be screened each year.

MAIN OUTCOME MEASURES

Cost effectiveness based on major outcomes averted, defined as pelvic inflammatory disease, ectopic pregnancy, infertility, or neonatal complications.

RESULTS

The incremental cost per major outcome averted for a programme of screening women only (assuming eight years of screening) was 22,300 pounds (33,000 euros; $45,000) compared with no organised screening. For a programme screening both men and women, the incremental cost effectiveness ratio was approximately 28,900 pounds. Pelvic inflammatory disease leading to hospital admission was the most frequently averted major outcome. The model was highly sensitive to the incidence of major outcomes and to uptake of screening. When both were increased the cost effectiveness ratio fell to 6200 pound per major outcome averted for screening women only.

CONCLUSIONS

Proactive register based screening for chlamydia is not cost effective if the uptake of screening and incidence of complications are based on contemporary empirical studies, which show lower rates than commonly assumed. These data are relevant to discussions about the cost effectiveness of the opportunistic model of chlamydia screening being introduced in England.

One to one interventions to reduce sexually transmitted infections and under the age of 18 conceptions: a systematic review of the economic evaluations

OBJECTIVE

To systematically review and critically appraise the economic evaluations of one to one interventions to reduce sexually transmitted infections (STIs) and teenage conceptions.

DESIGN

Systematic review.

DATA SOURCES

Search of four electronic bibliographic databases from 1990 to January 2006. Search keywords included teenage, pregnancy, adolescent, unplanned, unwanted, cost benefit, cost utility, economic evaluation, cost effectiveness and all terms for STIs, including specific diseases.

REVIEW METHODS

We included studies that evaluated a broad range of one to one interventions to reduce STIs. Outcomes included major outcomes averted, life years and quality adjusted life years (QALY). All studies were assessed against quality criteria.

RESULTS

Of 3,190 identified papers, 55 were included. The majority of studies found one to one interventions to be either cost saving or cost effective, although one highlighted the need to target the population to receive post-exposure prophylaxis to reduce transmission of HIV. Most studies used a static approach that ignores the potential re-infection of treated patients.

CONCLUSION

One to one interventions have been shown to be cost saving or cost effective but there are some limitations in applying this evidence to the UK policy context. More UK research using dynamic modelling approaches and QALYs would provide improved evidence, enabling more robust policy recommendations to be made about which one to one interventions are cost effective in reducing STIs in the UK setting. The results of this review can be used by policy makers, health economists and researchers considering further research in this area.

Risk selection and targeted interventions in community-based control of chlamydia

PURPOSE OF REVIEW

To describe recent developments in the community-based approach of high-risk groups for Chlamydia trachomatis infection, and to discuss the assessment of impact of selective systematic screening on the transmission of C. trachomatis in the community.

RECENT FINDINGS

Two large home-based screening programs in Europe have recently shown that systematic postal screening for C. trachomatis infection is feasible, but certain high-risk groups are poor participators. This underscores the need for risk selection and targeted approaches. A prediction rule has been developed which can assist in identifying high-risk groups and can be used as a tool for (self) selection for screening. The Internet has been shown to be a promising medium to promote chlamydia testing. School-based programs also succeed in including high-risk groups in screening programs. Recently developed dynamic simulation models, which take into account transmission of C. trachomatis, can assist in the development and evaluation of targeted screening strategies.

SUMMARY

Chlamydia will not likely be controlled by one standard approach. Risk selection strategies need further development and different systematic approaches at the community level, including postal screening, school-based screening, and the Internet may produce the desired public health effect of decreasing morbidity and reducing the transmission of C. trachomatis in the community.

Modelling the effectiveness of chlamydia screening in England

BACKGROUND

Several developed countries have initiated chlamydia screening programmes. Screening for a sexually transmitted infection has both direct individual and indirect population-wide effects. Mathematical models can incorporate these non-linear effects and estimate the likely impact of different screening programmes and identify areas where more data are needed.

METHODS

A stochastic, individual based dynamic network model, parameterised from UK screening studies and data on sexual behaviour and chlamydia epidemiology, was used to investigate the likely impact of opportunistic screening on chlamydia prevalence. Three main strategies were considered for <25 year olds: (1) annual offer to women; (2) annual offer to women or if changed partner within last 6 months; (3) annual offer to men and women. Sensitivity analyses were performed for key screening parameters including uptake rate, targeted age range, percentage of partners notified, and screening interval.

RESULTS

Under strategy 1, continuous opportunistic screening of women <25 years of age is expected to reduce the population prevalence by over 50% after 5 years. Prevalence is also expected to decrease in unscreened older women and in men. For all three strategies screening those aged over 25 results in small additional reductions in prevalence. Including men led to a faster and greater reduction in overall prevalence, but involved approximately twice as many tests as strategy 1 and 10% more than strategy 2. The frequency of attendance at healthcare sites limits the number of opportunities to screen and the effect of changing the screening interval.

CONCLUSIONS

The model suggests that continuous opportunistic screening at high uptake rates could significantly reduced chlamydia prevalence within a few years. Opportunistic programmes depend on regular attendance at healthcare providers, but there is a lack of high quality data on patterns of attendance. Inequalities in coverage may result in a less efficient and less equitable outcome.

Incidence of severe reproductive tract complications associated with diagnosed genital chlamydial infection: the Uppsala Women's Cohort Study

OBJECTIVE

To estimate the cumulative incidence of severe complications associated with genital chlamydia infection in the general female population.

METHODS

The Uppsala Women's Cohort Study was a retrospective population based cohort study in Sweden, linking laboratory, hospital, and population registers. We estimated the cumulative incidence of hospital diagnosed pelvic inflammatory disease, ectopic pregnancy, and infertility, and used multivariable regression models to estimate hazard ratios according to screening status.

RESULTS

We analysed complete data from 43 715 women in Uppsala aged 15-24 years between January 1985 and December 1989. Follow up until the end of 1999 included 709 000 woman years and 3025 events. The cumulative incidence of pelvic inflammatory disease by age 35 years was 3.9% (95% CI 3.7% to 4.0%) overall: 5.6% (4.7% to 6.7%) in women who ever tested positive for chlamydia, 4.0% (3.7% to 4.4%) in those with negative tests, and 2.9% (2.7% to 3.2%) in those who were never screened. The corresponding figures were: for ectopic pregnancy, 2.3% (2.2% to 2.5%) overall, 2.7% (2.1% to 3.5%), 2.0% (1.8% to 2.3%), and 1.9% (1.7% to 2.1%); and for infertility, 4.1% (3.9% to 4.3%) overall, 6.7% (5.7% to 7.9%), 4.7% (4.4% to 5.1%), and 3.1% (2.8% to 3.3%). Low educational attainment was strongly associated with the development of all outcomes.

CONCLUSIONS

The incidence of severe chlamydia associated complications estimated from ours, and other population based studies, was lower than expected. Studies that incorporate data about pelvic inflammatory disease diagnosed in primary care and behavioural risk factors would further improve our understanding of the natural history of chlamydia. Our results provide reassurance for patients, but mean that the benefits of chlamydia screening programmes might have been overestimated.

Screening for Chlamydia trachomatis: a systematic review of the economic evaluations and modelling

OBJECTIVE

To review systematically and critically, evidence used to derive estimates of costs and cost effectiveness of chlamydia screening.

METHODS

Systematic review. A search of 11 electronic bibliographic databases from the earliest date available to August 2004 using keywords including chlamydia, pelvic inflammatory disease, economic evaluation, and cost. We included studies of chlamydia screening in males and/or females over 14 years, including studies of diagnostic tests, contact tracing, and treatment as part of a screening programme. Outcomes included cases of chlamydia identified and major outcomes averted. We assessed methodological quality and the modelling approach used.

RESULTS

Of 713 identified papers we included 57 formal economic evaluations and two cost studies. Most studies found chlamydia screening to be cost effective, partner notification to be an effective adjunct, and testing with nucleic acid amplification tests, and treatment with azithromycin to be cost effective. Methodological problems limited the validity of these findings: most studies used static models that are inappropriate for infectious diseases; restricted outcomes were used as a basis for policy recommendations; and high estimates of the probability of chlamydia associated complications might have overestimated cost effectiveness. Two high quality dynamic modelling studies found opportunistic screening to be cost effective but poor reporting or uncertainty about complication rates make interpretation difficult.

CONCLUSION

The inappropriate use of static models to study interventions to prevent a communicable disease means that uncertainty remains about whether chlamydia screening programmes are cost effective or not. The results of this review can be used by health service managers in the allocation of resources, and health economists and other researchers who are considering further research in this area.

Prediction of costs, effectiveness, and disease control of a population-based program using home sampling for diagnosis of urogenital Chlamydia trachomatis Infections

OBJECTIVE

To estimate the incremental effects and costs of a home sampling screening approach for Chlamydia trachomatis over the current in-office screening practice in Denmark.

GOALS

To assess the effect of a new screening strategy.

STUDY DESIGN

A dynamic Monte Carlo model estimated prevalence and incidence over 10 years for a home sampling screening program and the current in-office screening. Subsequently, the incremental number of major outcomes averted (MOA) and the related direct and indirect costs were estimated.

RESULTS

Infection prevalence after 10 years was 1.0% with a home sampling program and 4.2% with the current in-office screening practice. The total costs per MOA reached 3186 US dollars during the first year of the home sampling strategy, but in year 4, the accumulated indirect costs offset the direct costs, and the program henceforth saved society costs.

CONCLUSIONS

Home sampling should be considered a relevant alternative to the current practice of in-office screening.

The impact of natural history parameters on the cost-effectiveness of Chlamydia trachomatis screening strategies

OBJECTIVE/GOAL

To understand the potential impact of assumptions about the natural history of untreated Chlamydia trachomatis on the cost-effectiveness of screening strategies.

STUDY DESIGN

Using a previously developed state-transition model, we explored how alternative assumptions about the natural history of disease following infection affect the estimated cost-effectiveness of screening for U.S. women. The analysis was conducted from a modified societal perspective and incorporated a lifetime analytic horizon.

RESULTS

Different natural history assumptions affect cost-effectiveness outcomes. Assumptions about the combined risk of persistent and repeat infections have the greatest impact on the composition of optimal screening strategies, whereas assumptions about the risk of pelvic inflammatory disease most greatly influenced the magnitude of incremental cost-effectiveness ratios.

CONCLUSIONS

Priorities for future C trachomatis research should include better estimates of the risk of pelvic inflammatory disease, persistence, and repeat infection. Better delineation of these variables will permit improved evaluation of potential screening activities.

The cost effectiveness of screening for genital Chlamydia trachomatis infection in Australia

Background: In Australia, there is no published study on the cost effectiveness of screening for chlamydia. The aim of this study was to examine the cost effectiveness of a hypothetical screening programme for chlamydia based on annual opportunistic testing of all women 25 years of age or younger consulting a general practitioner, compared with no screening. Methods: A decision–analytic modelling approach was used to determine the incremental cost effectiveness ratio (ICER) of screening compared with no screening over 25 years. The analysis measured Australian health-care costs and benefits were assessed in terms of quality-adjusted life years (QALYs). Results: The analysis resulted in a cost per QALY of $2968 for screening. One-way sensitivity analyses on all variables, and multi-way sensitivity analyses on some variables, showed a wide range for the cost effectiveness, from dominance (where screening is effective and saves money overall) to an ICER of $67 715 per QALY. Conclusions: The results indicate that annual opportunistic screening for chlamydia in women under 25 is a potentially worthwhile undertaking. However, the analysis also highlights uncertainties around the natural history of chlamydia and the effectiveness of chlamydia screening. Given these uncertainties, the need for further primary data collection in these areas becomes apparent.