Modelling the healthcare costs of an opportunistic chlamydia screening programme

Analysis of laboratory testing results collected in an enhanced chlamydia surveillance system in Australia, 2008-2010

BACKGROUND

Chlamydial infection is the most common notifiable disease in Australia, Europe and the US. Australian notifications of chlamydia rose four-fold from 20,274 cases in 2002 to 80,846 cases in 2011; the majority of cases were among young people aged less than 29 years. Along with test positivity rates, an understanding of the number of tests performed and the demographics of individuals being tested are key epidemiological indicators. The ACCESS Laboratory Network was established in 2008 to address this issue.

METHODS

The ACCESS Laboratory Network collected chlamydia testing data from 15 laboratories around Australia over a three-year period using data extraction software. All chlamydia testing data from participating laboratories were extracted from the laboratory information system; patient identifiers converted to a unique, non-reversible code and de-identified data sent to a single database. Analysis of data by anatomical site included all specimens, but in age and sex specific analysis, only one testing episode was counted.

RESULTS

From 2008 to 2010 a total of 628,295 chlamydia tests were referred to the 15 laboratories. Of the 592,626 individual episodes presenting for testing, 70% were from female and 30% from male patients. In female patients, chlamydia positivity rate was 6.4% overall; the highest rate in 14 year olds (14.3%). In male patients, the chlamydia positivity rate was 9.4% overall; the highest in 19 year olds (16.5%). The most common sample type was urine (57%). In 3.2% of testing episodes, multiple anatomical sites were sampled. Urethral swabs gave the highest positivity rate for all anatomical sites in both female (7.7%) and male patients (14%), followed by urine (7.6% and 9.4%, respectively) and eye (6.3% and 7.9%, respectively).

CONCLUSIONS

The ACCESS Laboratory Network data are unique in both number and scope and are representative of chlamydia testing in both general practice and high-risk clinics. The findings from these data highlight much lower levels of testing in young people aged 20 years or less; in particular female patients aged less than 16 years, despite being the group with the highest positivity rate. Strategies are needed to increase the uptake of testing in this high-risk group.

For the proposition: for the diagnosis of viral infections, commercial assays provide more reliable results than do in-house assays

It cannot be disputed that in-house ('home brew') assays have a part to play in the diagnosis of emerging or evolving infections such as avian influenza H5N1. In such circumstances, diagnostic companies can provide Research Use Only (RUO) or analyte specific reagents (ASR) to facilitate development. In contrast, the provision of commercial assays is governed by regulatory approval and subject to regular audit by the relevant regulatory bodies to ensure continued quality process throughout the continuum of product management. From initial design, through to post-launch support, the process has to meet the requirements of the USA Food and Drug Administration (FDA) Quality System Regulation (FDA, 1996) as well as that of the international quality standards, for example ISO 9001 (Int. Standard ISO 9001, 2000). Because of the quality policies that are implemented in the commercial environment, I will argue that, where available, commercial assays should replace in-house methods in order to ensure long term reliability of results.

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.

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.

Healthcare and patient costs of a proactive chlamydia screening programme: the Chlamydia Screening Studies project

BACKGROUND AND OBJECTIVE

Most economic evaluations of chlamydia screening do not include costs incurred by patients. The objective of this study was to estimate both the health service and private costs of patients who participated in proactive chlamydia screening, using mailed home-collected specimens as part of the Chlamydia Screening Studies project.

METHODS

Data were collected on the administrative costs of the screening study, laboratory time and motion studies and patient-cost questionnaire surveys were conducted. The cost for each screening invitation and for each accepted offer was estimated. One-way sensitivity analysis was conducted to explore the effects of variations in patient costs and the number of patients accepting the screening offer.

RESULTS

The time and costs of processing urine specimens and vulvo-vaginal swabs from women using two nucleic acid amplification tests were similar. The total cost per screening invitation was 20.37 pounds (95% CI 18.94 pounds to 24.83). This included the National Health Service cost per individual screening invitation 13.55 pounds (95% CI 13.15 pounds to 14.33) and average patient costs of 6.82 pounds (95% CI 5.48 pounds to 10.22). Administrative costs accounted for 50% of the overall cost.

CONCLUSIONS

The cost of proactive chlamydia screening is comparable to those of opportunistic screening. Results from this study, which is the first to collect private patient costs associated with a chlamydia screening programme, could be used to inform future policy recommendations and provide unique primary cost data for economic evaluations.

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.

Fitness cost due to mutations in the 16S rRNA associated with spectinomycin resistance in Chlamydia psittaci 6BC

The fitness cost of a resistance determinant is the primary parameter that determines its frequency in vivo. As a model for analysis of the impact of drug resistance mutations on the intracellular life cycle of Chlamydia spp., we studied the growth of four genetically defined spectinomycin-resistant (Spc(r)) clonal variants of Chlamydia psittaci 6BC isolated in the plaque assay. The development of each variant was monitored over 46 h postinfection in the absence of drug, either in pure culture or in 1:1 competition with the parent strain. Spc(r) mutations in the 16S rRNA gene at positions 1191 and 1193 were associated with a marked impairment of C.psittaci biological fitness, and the bacteria were severely out-competed by the wild-type parent. In contrast, mutations at position 1192 had minor effects on the bacterial life cycle, allowing the resistant isolates to compete more efficiently with the wild-type strain. Thus, mutations with a wide range of fitness costs can be selected in the plaque assay, providing a new strategy for prediction and monitoring of the emergence of antibiotic resistance in chlamydiae. So far, drug resistance has not been a serious threat for the treatment of chlamydial infections. Tetracycline is an effective antichlamydial drug that targets 16S rRNA. Attempts to isolate spontaneous tetracycline-resistant mutants of C. psittaci 6BC revealed a frequency <3 x 10(-9). We suggest that the rarity of genotypic antibiotic resistance among chlamydial clinical isolates reflects the deleterious effects of such mutations on the fitness of these obligate intracellular bacteria in the host.

Chlamydia screening in general practice: views of professionals on the key elements of a successful programme

OBJECTIVES

Chlamydia trachomatis is a common sexually transmitted infection with serious consequences if not treated. Chlamydia screening pilots in England have established feasibility in primary care but there are currently no examples of good practice in general practice. The objectives of the study were to understand issues of using general practice as a setting for chlamydia screening and to explore ways of implementing a successful screening strategy.

METHODS

Based on findings of a literature review, a semi-structured schedule was constructed to interview a purposive sample of policymakers, consultants in sexual and reproductive health and primary care professionals. A thematic framework was used for qualitative analysis.

RESULTS

Twenty-two themes were identified and were ranked in order of word count. The topic that generated most discussion was heterogeneity of knowledge, attitudes and skills in general practice. When broken down by professional group, this topic ranked the highest for practice nurses and consultants in sexual health; general practitioners (GPs) and the chlamydia screening coordinator spoke most about financial incentives while the public health consultant spoke most about access.

CONCLUSIONS

Most believed screening can and should be done and general practice can offer better population coverage. It needs to have little impact on clinicians' workload, for example, by using urine tests and self-taken vaginal swabs. Financial recognition needs to reflect the administrative costs and the impact on reception staff, but this and the innovative tests might add to the cost of the screening programme. Incentives have to be handled sensitively to reduce inequity among GPs and other services offering screening.

Partner notification of chlamydia infection in primary care: randomised controlled trial and analysis of resource use

OBJECTIVE

To evaluate the effectiveness of a practice nurse led strategy to improve the notification and treatment of partners of people with chlamydia infection.

DESIGN

Randomised controlled trial.

SETTING

27 general practices in the Bristol and Birmingham areas.

PARTICIPANTS

140 men and women with chlamydia (index cases) diagnosed by screening of a home collected urine sample or vulval swab specimen.

INTERVENTIONS

Partner notification at the general practice immediately after diagnosis by trained practice nurses, with telephone follow up by a health adviser; or referral to a specialist health adviser at a genitourinary medicine clinic.

MAIN OUTCOME MEASURES

Primary outcome was the proportion of index cases with at least one treated sexual partner. Specified secondary outcomes included the number of sexual contacts elicited during a sexual history, positive test result for chlamydia six weeks after treatment, and the cost of each strategy in 2003 sterling prices.

RESULTS

65.3% (47/72) of participants receiving practice nurse led partner notification had at least one partner treated compared with 52.9% (39/68) of those referred to a genitourinary medicine clinic (risk difference 12.4%, 95% confidence interval -1.8% to 26.5%). Of 68 participants referred to the clinic, 21 (31%) did not attend. The costs per index case were 32.55 pounds sterling for the practice nurse led strategy and 32.62 pounds sterling for the specialist referral strategy.

CONCLUSION

Practice based partner notification by trained nurses with telephone follow up by health advisers is at least as effective as referral to a specialist health adviser at a genitourinary medicine clinic, and costs the same. Trial registration Clinical trials: NCT00112255.