Chlamydia became a nationally notifiable disease in 1995, and shortly thereafter, the Centers for Disease Control and Prevention released national chlamydia screening recommendations and other control strategies related to treatment and partner management.1 In 2014, an all-time high of more than 1.4 million chlamydia cases were reported, far exceeding any other reportable communicable disease.2 The strategy for chlamydia control has focused on implementing widespread screening of sexually active young women to detect asymptomatic infections and prevent adverse reproductive outcomes such as pelvic inflammatory disease (PID), ectopic pregnancy, and tubal factor infertility.
Federal support for chlamydia screening began in 1988 as a demonstration project in US Public Health Service Region X. In 1993, congressional legislation authorized an expansion known as the Infertility Prevention Program (IPP), a collaboration between the Centers for Disease Control and Prevention and the Office of Population Affairs.3 By the mid-1990s, sexually transmitted disease (STD) programs across the nation were collaborating with Title X-funded family planning agencies to implement widespread screening of young women. It was not until 1996 that the first randomized trial demonstrating the benefit of chlamydia screening was published,4 which prompted national recommendations from the US Preventive Services Task Force,5 and inclusion of chlamydia screening as a national healthcare performance measure.6 To match the scale of numbers of young women at risk and the associated undetected chlamydia burden projected from the original prevalence studies, significant annual investment was placed in IPP to enable screening of young women seeking care in family planning, STD clinics, and correctional settings. IPP funding ended December 2013 as chlamydia screening became standard of care for young women and alternative sources of funding were identified.
For population-level observational studies, it is not unreasonable to expect that screening and treatment of a common communicable disease would lead to reduced burden of infection in the population–decreased prevalence and incidence. Although reductions in positivity among screened populations were observed in the early years of IPP, there has been little evidence for sustained reduction in chlamydia burden.7 Several parallel sentinel (e.g., IPP and National Job Training Program8) and population-level (e.g., National Health and Nutrition Examination Survey9) surveillance systems were enlisted to monitor trends in chlamydia positivity. All have demonstrated declines in conjunction with chlamydia screening, but declines have not been sustained. Meanwhile, annual chlamydia incidence, as measured by government public health surveillance systems in the United States, steadily increased from the late 90s until very recently when rates began to plateau at their highest level.2 These increases are at least partially explained by increased detection and reporting of infection, including improvements in the sensitivity of diagnostic tests. Interpreting incidence as a measure of transmission is especially challenging because chlamydia infection in women is largely asymptomatic.
Why does chlamydia prevalence seem to be stable while incidence seems to be rising? There are a number of scenarios to consider from biological, behavioral, and clinical practice perspectives. Were there changes in pathogenicity or transmissibility of the circulating strains? What if the optimal screening interval to identify asymptomatic infection should actually be shorter than current annual screening to reduce the time for complications to develop? What is the true benefit of screening in the detection of long-standing prevalent infection that causes low-grade inflammation that leads to scarring and long-term complications? What is the role of trends in risk behaviors (condom use, multiple and concurrent partner) in response to cultural shifts? Perhaps the earlier declines in chlamydia positivity resulted from fear of HIV, with a concomitant increase in protective behaviors and decrease in STDs overall. Does timely treatment reduce the immunological response and increase the size of the susceptible population? Are recent declines in incidence among adolescent females a reflection of reduced infection or reduced screening, or both? To what extent do increases in access and use of male urine-based tests contribute to decreased transmission?
Interpreting trends in PID as the outcome of interest for chlamydia prevention has been subject to similar dilemmas. In the United States and western Europe, trends in both hospital discharges and outpatient diagnoses show consistent marked declines in parallel with expansion of chlamydia screening rates.2,10 However, these population-level associations are fundamentally ecological such that reductions in PID could be explained by concurrent changes in management standards favoring outpatient treatment. Furthermore, the accuracy and validity of studies using administrative or billing data are limited by variations in coding practices and case capture techniques. Quantifying the true benefits of chlamydia screening remains elusive with available data.
In a recent analysis, Moore et al.11 try in earnest to address this critical question by triangulating multiple diverse data sources to creatively examine chlamydia and gonorrhea infections and related diagnoses that function as outcomes of screening as well as predictors of PID outcomes. The authors evaluated trends over a 23-year period (1988–2010) in 4 outcomes: PID, ectopic pregnancy, gonorrhea incidence, and chlamydia positivity in family planning settings. Although concurrent declines were observed in all 4 outcomes, the overall picture remained mixed in that the steepest declines occurred within the first 6 years of the observation period. Stronger associations were observed between infection outcomes and inpatient PID and ectopic pregnancy, which may indicate that improved detection and treatment yielded the greatest benefit in reducing the most severe complications.
Limitations of using these 4 outcomes were apparent. Both reported case rates and positivity could have been used because all of the reasons cited for rejecting case rates–changes in populations being screened and number and type of tests performed–pertain to positivity, even with somewhat stable clinics contributing to data. Furthermore, these confounding factors also affected measurements and interpretation of gonorrhea incidence, particular among women, half of whom have no symptoms and thus depend on screening to identify their infections. The authors' conclusions rested upon a complex array of assumptions and estimations which were needed to overcome limits in their population surveillance, sentinel surveillance, and administrative data sources. For instance, IPP positivity data were applied to the statewide female population. Similarly, the application of national outpatient PID/ectopic pregnancy rates to Washington and the triangulation of data from one health plan to further adjust ectopic pregnancy rates had unclear validity. These limitations are a reminder of ongoing challenges to measuring meaningful outcomes of chlamydia screening.
Relying on existing case-based surveillance and sentinel prevalence monitoring for the evaluation of chlamydia screening requires accounting for the myriad provider and laboratory factors which affect trends in those measures. Case-based surveillance data are influenced by changes in reporting mandates, adherence to, and mechanisms for reporting, such as electronic laboratory reporting; screening practices, test volume, and changes in populations tested; on-site testing and presumptive treatment; changes in test technology that alter sensitivity or specificity, and availability and use of rectal and throat specimens; and rates of partner testing in the context of increasing expedited partner treatment.
Moore and colleagues' analytical approach of triangulating multiple data sources on chlamydia infections and adverse outcomes is the latest in efforts to demonstrate the impact of chlamydia screening on a population basis. But given the different populations that these observational data sources represent, whether examined here in the United States or in Europe, it remains difficult to satisfy the basic tenets of causality. Low has argued that 2 other approaches are more compelling: (1) randomized controlled trials of chlamydia screening on a population level and (2) modeling the impact of chlamydia control programs in a population by including multiple parameters such as screening coverage, partner management, and screening for repeat infection to assess the potential reduction in PID risk.12 Are these alternative approaches informative for implementing population-level chlamydia screening? Beyond the Scholes trial that demonstrated a 60% reduction in risk of PID, subsequent trials have been less compelling. The Prevention of Pelvic Infection trial in the UK was unable to demonstrate a significant decreased PID incidence among participants due to lower-than-anticipated PID incidence and consequent lack of statistical power to detect an effect.13 Conducting modeling to address the limitations and feasibility issues associated with randomized trial approaches has been an attractive alternative to evaluating the benefits of chlamydia screening for PID prevention.14 Unfortunately, public health programs are hard pressed to demonstrate return on investment in expanded chlamydia screening programs and must rely on observational data collected from surveillance and health program data, which reflect the gap between idealized scenarios and real-world challenges in screening uptake, inadequate partner treatment, and low rates of repeat screening.15,16
Advances in health information technology offer promising opportunities to reconsider the utility of observational data for evaluating the benefit of chlamydia screening.17 The transition to capturing medical information in electronic health records that integrate clinical, laboratory, and pharmacy data enables the creation of registries and cohorts of patients who are eligible for and receive sexual health care. By leveraging Meaningful Use requirements for providers who transition to electronic health records,18,19 the potential for having systematic capture of chlamydia testing, treatment, partner management, and repeat infection as well as PID outcomes becomes more apparent. Indeed, such systems facilitate clinical decision support tools such as automated reminders to both providers and patients for improving adherence to chlamydia screening, treatment and retesting recommendations, further ensuring improved uptake of these prevention strategies. The development of health information exchanges further synergizes the ability of diverse providers across a community to take advantage of these tools and increases the access to sexual health services as well as other population databases, including birth records and hospital and emergency room discharge data.20 But from a program perspective, there are population-level data with higher consistency and validity in measuring who receives what services and experiences what relevant outcomes, all of which contribute to more robust evaluation of these services. We must also acknowledge, though, that to achieve such population health data integration and to maximize the benefits of evaluation also requires additional expertise in informatics and adept data mining. Given the high volume of morbidity and many unanswered questions regarding public health interventions, major investments are needed to support informatics capacity building, training, and infrastructure in the STD field.
In conjunction with advances in information technology and analytic capacities, it is important to consider the role of data policy issues. Ensuring data security and confidentiality are paramount. Striking a balance between preventing breaches of confidentiality and ensuring access to data for public health data analyses is critical. Unnecessary restrictions that limit access and use of data risk delays in understanding key population health threats and benefits of public health and clinical interventions. With greater legal protections against discrimination and loss of health care coverage due to preexisting conditions, current data security policies may need to be reexamined.
Public health programs have the health information technology tools to build surveillance systems that can demonstrate a return on investment in population-based chlamydia control efforts. These efforts must involve integrating health data from all health providers, across settings, and populations served to minimize the pitfalls of fragmented services and isolated data systems. By fostering collaborations between STD and family planning agencies to implement and evaluate chlamydia screening programs on a regional level, IPP was a step in this direction.21 The program data systems supporting IPP have been the basis for continuous quality improvement related to screening, treatment, and partner management, and are a model for how further integration and capture of reproductive outcomes may be accomplished with the move to electronic health records. Title X and family planning partners continue to be key players in providing STD clinical services to at-risk populations. Since the 1990s, many of these clinics began providing care for gay, bisexual and other men who have sex with men, and transgender patients. With the closures of many publicly-funded categorical STD clinics, these community partners have become a core component of STD control in the United States. Under the Affordable Care Act, this model of best practices in chlamydia prevention strategies can further extend to other public sector programs providing primary care and be a resource to private sector managed care providers. Using the integrated data from all of these programs to demonstrate return on investment can provide the evidence needed to support chlamydia screening programs in the future.
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