Estimating Local Chlamydia Incidence and Prevalence Using Surveillance Data

Prognostic Value of Anti-Chlamydia Trachomatis IgG in Breast Cancer and the Modification Effects of Pro-Inflammatory Cytokines: A 13-Year Prospective Cohort Study

Purpose

Chlamydia trachomatis (C. trachomatis) is associated with several gynecological tumors; yet its prognostic role in breast cancer remains unclear. Thus, we investigated the prognostic role of anti-C. trachomatis immunoglobulin G (IgG) in breast cancer patients and the modification effects of pro-inflammatory cytokines.

Methods

The serum levels of C. trachomatis IgG and four pro-inflammatory cytokines were measured. Cox regression was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs), including product terms to assess the modification effects of pro-inflammatory cytokines on the association between C. trachomatis IgG and breast cancer prognosis.

Results

From 2008 to 2018, 1121 breast cancer patients were recruited and followed up until December 31, 2021, with a median follow-up time of 63.91 months (interquartile range: 39.16-90.08 months). Patients positive for C. trachomatis IgG showed HRs of 1.09 (95% CI, 0.67-1.78) for overall survival (OS) and 1.24 (0.87-1.78) for progression-free survival (PFS), compared to those who were negative. These associations became statistically significant in women aged 50 years or younger (HR=1.43, 95% CI=0.79-2.58 for OS; HR=1.79, 95% CI=1.16-2.77 for PFS). Positive C. trachomatis IgG serology was associated with adverse prognostic effects among patients with higher levels of pro-inflammatory cytokines (IL-6, TNF-α, IL-8, and IL-1β), but with favorable prognostic effects for those with low levels. These interactions were particularly significant in those aged 50 years or younger.

Conclusion

In breast cancer patients younger than 50 years of age or with higher levels of pro-inflammatory cytokines, C. trachomatis infection appeared to have a negative prognostic impact. These findings highlight the significance of C. trachomatis in predicting prognosis and personalized therapy for breast cancer patients.

Using infection prevalence, seroprevalence and case report data to estimate chlamydial infection incidence

OBJECTIVES

To measure the effectiveness of chlamydia control strategies, we must estimate infection incidence over time. Available data, including survey-based infection prevalence and case reports, have limitations as proxies for infection incidence. We therefore developed a novel method for estimating chlamydial incidence.

METHODS

We linked a susceptible infectious mathematical model to serodynamics data from the National Health and Nutritional Examination Survey, as well as to annual case reports. We created four iterations of this model, varying assumptions about how the method of infection clearance (via treatment seeking, routine screening or natural clearance) relates to long-term seropositivity. Using these models, we estimated annual infection incidence for women aged 18-24 and 25-37 years in 2014. To assess model plausibility, we also estimated natural clearance for the same groups.

RESULTS

Of the four models we analysed, the model that best explained the empirical data was the one in which longer-lasting infections, natural clearance and symptomatic infections all increased the probability of long-term seroconversion. Using this model, we estimated 5910 (quartile (Q)1, 5330; Q3, 6500) incident infections per 100 000 women aged 18-24 years and 2790 (Q1, 2500; Q3, 3090) incident infections per 100 000 women aged 25-37 years in 2014. Furthermore, we estimated that natural clearance rates increased with age.

CONCLUSIONS

Our method can be used to estimate the number of chlamydia infections each year, and thus whether infection incidence increases or decreases over time and after policy changes. Furthermore, our results suggest that clearance via medical intervention may lead to short-term or no seroconversion, and the duration of untreated chlamydial infection may vary with age, underlining the complexity of chlamydial infection dynamics.

A profile of the binx health io® molecular point-of-care test for chlamydia and gonorrhea in women and men

Introduction: Point-of-care (POC) tests for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are urgently needed to control the STI epidemic in order to offer patients an immediate diagnoses and accurate treatment before they leave a clinical encounter and thus reduce transmission and sequelae. Nucleic acid amplification tests (NAATs) have increased sensitivity and specificity, but very few POC assays can provide results of such tests within the usual time of the patient visit.Areas covered: This review describes the technology and performance characteristics of the binx health io® [Boston, MA] (binx io) CT/NG assay, a new rapid molecular POC assay. The assay is compared to other available molecular POC tests. We also describe the importance of time to results and assay performance for this POC assay.Expert opinion: The binx io CT/NG assay offers the ability to incorporate the use of POC tests to identify and immediately treat chlamydia and gonococcal infections into the clinical visit, which will provide improved outcomes for patients. Additional implementation studies are needed to optimize the adoption of this new test.

Per-partnership transmission probabilities for Chlamydia trachomatis infection: evidence synthesis of population-based survey data

Background

Chlamydia is the most commonly diagnosed sexually transmitted infection worldwide. Mathematical models used to plan and assess control measures rely on accurate estimates of chlamydia’s natural history, including the probability of transmission within a partnership. Several methods for estimating transmission probability have been proposed, but all have limitations.

Methods

We have developed a new model for estimating per-partnership chlamydia transmission probabilities from infected to uninfected individuals, using data from population-based surveys. We used data on sexual behaviour and prevalent chlamydia infection from the second UK National Study of Sexual Attitudes and Lifestyles (Natsal-2) and the US National Health and Nutrition Examination Surveys 2009–2014 (NHANES) for Bayesian inference of average transmission probabilities, across all new heterosexual partnerships reported. Posterior distributions were estimated by Markov chain Monte Carlo sampling using the Stan software.

Results

Posterior median male-to-female transmission probabilities per partnership were 32.1% [95% credible interval (CrI) 18.4–55.9%] (Natsal-2) and 34.9% (95%CrI 22.6–54.9%) (NHANES). Female-to-male transmission probabilities were 21.4% (95%CrI 5.1–67.0%) (Natsal-2) and 4.6% (95%CrI 1.0–13.1%) (NHANES). Posterior predictive checks indicated a well-specified model, although there was some discrepancy between reported and predicted numbers of partners, especially in women.

Conclusions

The model provides statistically rigorous estimates of per-partnership transmission probability, with associated uncertainty, which is crucial for modelling and understanding chlamydia epidemiology and control. Our estimates incorporate data from several sources, including population-based surveys, and use information contained in the correlation between number of partners and the probability of chlamydia infection. The evidence synthesis approach means that it is easy to include further data as it becomes available.

The Influence of Screening, Misclassification, and Reporting Biases on Reported Chlamydia Case Rates Among Young Women in the United States, 2000 Through 2017

BACKGROUND

National chlamydia case rate trends are difficult to interpret because of biases from partial screening coverage, imperfect diagnostic tests, and underreporting. We examined the extent to which these time-varying biases could influence reported annual chlamydia case rates.

METHODS

Annual reported case rates among women aged 15 through 24 years from 2000 through 2017 were obtained from the Centers for Disease Control and Prevention's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention AtlasPlus tool. Estimates of reporting completeness, diagnostic test sensitivity and specificity, and screening coverage were derived from literature review and expert opinion. We adjusted annual reported case rates for incomplete reporting, imperfect diagnostic tests, and partial screening coverage through a series of corrections, and calculated annual adjusted case rates of correctly diagnosed chlamydia.

RESULTS

Adjusted chlamydia case rates among young women were higher than reported case rates throughout the study period. Reported case rates increased over the study period, but adjusted rates declined from 12,900 to 7900 cases per 100,000 person-years between 2000 and 2007. After 2007, adjusted case rates declined to 7500 cases per 100,000 person-years in 2017. Bias from partial screening coverage had a larger impact on case rate magnitude and trend shape than bias from imperfect diagnostic tests or underreporting.

CONCLUSIONS

Reported chlamydia case rates may be substantially lower than true chlamydia case rates because of incomplete reporting, imperfect diagnostic tests, and partial screening coverage. Because the magnitude of these biases has declined over time, the differences between reported and adjusted case rates have narrowed, revealing a sharp decline in adjusted case rates even as reported case rates have risen. The decline in adjusted case rates suggests that the rise in reported case rates should not be interpreted strictly as increasing chlamydia incidence, as the observed rise can be explained by improvements in screening coverage, diagnostic tests, and reporting.

Understanding Relationships Between Chlamydial Infection, Symptoms, and Testing Behavior: An Analysis of Data from Natsal-3

Supplemental Digital Content is available in the text.

Genital chlamydia is the most commonly diagnosed sexually transmitted infection worldwide and can have serious long-term sequelae. Numerous countries invest substantially in testing but evidence for programs’ effectiveness is inconclusive. It is important to understand the effects of testing programs in different groups of people.

Optimizing Strategies for Chlamydia trachomatis and Neisseria gonorrhoeae Screening in Men Who Have Sex With Men: A Modeling Study

BACKGROUND

International guidelines recommend the systematic screening for Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) infections in all men who have sex with men (MSM) who have engaged in unprotected sex. However, the optimal screening strategy remains unclear. We developed a modeling approach to optimize NG/CT screening strategy in MSM.

METHODS

A compartmental model of NG/CT screening and infection was implemented. NG/CT anal, pharyngeal, and urine (APU) samples from MSM attending the sexually transmitted infections clinic were used to estimate the screening rate, prevalence, and incidence in a base case scenario. Different screening strategies (scenarios; S) were then evaluated: APU samples every 12 months (S1); APU samples every 3 months (S2); APU samples every 6 months (S3); anal and pharyngeal (AP) samples every 6 months (S4); and AP samples every 3 months (S5).

RESULTS

We analyzed 2973 triplet APU samples from 1255 patients. We observed 485 NG and 379 CT diagnoses. NG/CT prevalence and incidence estimates were 12.0/11.1% and 40/29 per 100 person-years, respectively, in the base case scenario. As compared to S2, the reference strategy, the proportions of missed NG/CT diagnoses were 42.0/41.2% with S1, 21.8/22.5% with S3, 25.6/28.3% with S4, and 6.3/10.5% with S5, respectively. As compared to S2, S1 reduced the cost of the analysis by 74%, S3 by 50%, S4 by 66%, and S5 by 33%. The numbers needed to screen for catching up the missed NG/CT diagnoses were 49/67 with S1, 62/82 with S3, 71/87 with S4, and 143/118 with S5.

CONCLUSIONS

S5 appears to be the best strategy, missing only 6.3/10.5% of NG/CT diagnoses, for a cost reduction of 33%.

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

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

Assessing local chlamydia screening performance by combining survey and administrative data to account for differences in local population characteristics

Reducing health inequalities requires improved understanding of the causes of variation. Local-level variation reflects differences in local population characteristics and health system performance. Identifying low- and high-performing localities allows investigation into these differences. We used Multilevel Regression with Post-stratification (MRP) to synthesise data from multiple sources, using chlamydia testing as our example. We used national probability survey data to identify individual-level characteristics associated with chlamydia testing and combined this with local-level census data to calculate expected levels of testing in each local authority (LA) in England, allowing us to identify LAs where observed chlamydia testing rates were lower or higher than expected, given population characteristics. Taking account of multiple covariates, including age, sex, ethnicity, student and cohabiting status, 5.4% and 3.5% of LAs had testing rates higher than expected for 95% and 99% posterior credible intervals, respectively; 60.9% and 50.8% had rates lower than expected. Residual differences between observed and MRP expected values were smallest for LAs with large proportions of non-white ethnic populations. London boroughs that were markedly different from expected MRP values (≥90% posterior exceedance probability) had actively targeted risk groups. This type of synthesis allows more refined inferences to be made at small-area levels than previously feasible.

Epidemiological Trends of Antibiotic Resistant Gonorrhoea in the United Kingdom

Gonorrhoea is one of the most common sexually-transmitted bacterial infections, globally and in the United Kingdom. The levels of antibiotic resistance in gonorrhoea reported in recent years represent a critical public health issue. From penicillins to cefixime, the gonococcus has become resistant to all antibiotics that have been previously used against it, in each case only a matter of years after introduction as a first-line therapy. After each instance of resistance emergence, the treatment recommendations have required revision, to the point that only a few antibiotics can reliably be prescribed to treat infected individuals. Most countries, including the UK, now recommend that gonorrhoea be treated with a dual therapy combining ceftriaxone and azithromycin. While this treatment is still currently effective for the vast majority of cases, there are concerning signs that this will not always remain the case, and there is no readily apparent alternative. Here, we review the use of antibiotics and epidemiological trends of antibiotic resistance in gonorrhoea from surveillance data over the past 15 years in the UK and describe how surveillance could be improved.

Changes in chlamydia prevalence and duration of infection estimated from testing and diagnosis rates in England: a model-based analysis using surveillance data, 2000-15

BACKGROUND

Chlamydia screening programmes have been implemented in several countries, but the effects of screening on incidence, prevalence, and reproductive sequelae remain unclear. In England, despite increases in testing with the rollout of the National Chlamydia Screening Programme (NCSP; 2003-08), prevalence estimated in 10-yearly population-based surveys was similar before (1999-2001) and after (2010-12) the programme. However, the precision of these previous estimates was limited by the low numbers of infections. We aimed to establish annual, rather than 10-yearly, estimates of chlamydia prevalence and infection duration.

METHODS

In this model-based analysis, we used previously published minimum and maximum estimates and Public Health England data for chlamydia test coverage and diagnoses in men and women aged 15-24 years in England, before, during, and after the scale-up of national chlamydia screening. We used a mechanistic model, which accounted for symptomatic chlamydia testing and asymptomatic screening, to estimate changes in prevalence and average duration of infections for each year. We describe estimates derived from the maximum and minimum numbers of tests and diagnoses as maximum and minimum estimates, regardless of their relative magnitude.

FINDINGS

The data included numbers of tests and diagnoses in men and women aged 15-19 years and 20-24 years in England each year from 2000 to 2015. We estimated reductions in prevalence and average infection duration in both sexes once screening was fully implemented. From 2008 to 2010, estimated posterior median prevalence reductions in people aged 15-24 years were 0·68 percentage points (95% credible interval 0·26-1·40; minimum) and 0·66 percentage points (0·25-1·37; maximum) for men and 0·77 percentage points (0·45-1·27) for women (minimum and maximum estimates were the same for women). Over the same time period, mean duration of infection reduced by 75 days (95% credible interval 17-255; minimum) and 74 days (95% credible interval 17-247; maximum) in men and 30 days (22-40) in women. Since 2010, some of the progress made by the NCSP has been reversed, alongside a reduction in testing.

INTERPRETATION

Our analysis provides the first evidence for a reduction in chlamydia prevalence in England concurrent with large-scale population testing. It also shows a consistent decline in the average duration of infections, which is a measure of screening effectiveness that is unaffected by behavioural changes.

FUNDING

National Institute for Health Research, Medical Research Council.

Should we screen for the sexually-transmitted infection Mycoplasma genitalium? Evidence synthesis using a transmission-dynamic model

There is increasing concern about Mycoplasma genitalium as a cause of urethritis, cervicitis, pelvic inflammatory disease (PID), infertility and ectopic pregnancy. Commercial nucleic acid amplification tests (NAATs) are becoming available, and their use in screening for M. genitalium has been advocated, but M. genitalium's natural history is poorly-understood, making screening's effectiveness unclear. We used a transmission-dynamic compartmental model to synthesise evidence from surveillance data and epidemiological and behavioural studies to better understand M. genitalium's natural history, and then examined the effects of implementing NAAT testing. Introducing NAAT testing initially increases diagnoses, by finding a larger proportion of infections; subsequently the diagnosis rate falls, due to reduced incidence. Testing only symptomatic patients finds relatively little infection in women, as a large proportion is asymptomatic. Testing both symptomatic and asymptomatic patients has a much larger impact and reduces cumulative PID incidence in women due to M. genitalium by 31.1% (95% range:13.0%-52.0%) over 20 years. However, there is important uncertainty in M. genitalium's natural history parameters, leading to uncertainty in the absolute reduction in PID and sequelae. Empirical work is required to improve understanding of key aspects of M. genitalium's natural history before it will be possible to determine the effectiveness of screening.

Should we screen for the sexually-transmitted infection Mycoplasma genitalium? Evidence synthesis using a transmission-dynamic model

There is increasing concern about Mycoplasma genitalium as a cause of urethritis, cervicitis, pelvic inflammatory disease (PID), infertility and ectopic pregnancy. Commercial nucleic acid amplification tests (NAATs) are becoming available, and their use in screening for M. genitalium has been advocated, but M. genitalium's natural history is poorly-understood, making screening's effectiveness unclear. We used a transmission-dynamic compartmental model to synthesise evidence from surveillance data and epidemiological and behavioural studies to better understand M. genitalium's natural history, and then examined the effects of implementing NAAT testing. Introducing NAAT testing initially increases diagnoses, by finding a larger proportion of infections; subsequently the diagnosis rate falls, due to reduced incidence. Testing only symptomatic patients finds relatively little infection in women, as a large proportion is asymptomatic. Testing both symptomatic and asymptomatic patients has a much larger impact and reduces cumulative PID incidence in women due to M. genitalium by 31.1% (95% range:13.0%-52.0%) over 20 years. However, there is important uncertainty in M. genitalium's natural history parameters, leading to uncertainty in the absolute reduction in PID and sequelae. Empirical work is required to improve understanding of key aspects of M. genitalium's natural history before it will be possible to determine the effectiveness of screening.

Genital Chlamydia trachomatis Infections Clear More Slowly in Men Than Women, but Are Less Likely to Become Established

Background

Rigorous estimates for clearance rates of untreated chlamydia infections are important for understanding chlamydia epidemiology and designing control interventions, but were previously only available for women.

Methods

We used data from published studies of chlamydia-infected men who were retested at a later date without having received treatment. Our analysis allowed new infections to take one of 1, 2, or 3 courses, each clearing at a different rate. We determined which of these 3 models had the most empirical support.

Results

The best-fitting model had 2 courses of infection in men, as was previously found for women: “slow-clearing” and “fast-clearing.” Only 68% (57%–78%) (posterior median and 95% credible interval [CrI]) of incident infections in men were slow-clearing, vs 77% (69%–84%) in women. The slow clearance rate in men (based on 6 months’ follow-up) was 0.35 (.05–1.15) year^-1 (posterior median and 95% CrI), corresponding to mean infection duration 2.84 (.87–18.79) years. This compares to 1.35 (1.13–1.63) years in women.

Conclusions

Our estimated clearance rate is slower than previously assumed. Fewer infections become established in men than women but once established, they clear more slowly. This study provides an improved description of chlamydia’s natural history to inform public health decision making. We describe how further data collection could reduce uncertainty in estimates.