bluuebunny/crossref_metadata_2025_split huggingface dataset:
P1-S4.15 Revisiting HIV epidemic appraisals for assisting in the design of effective HIV prevention programs
Authors: Mishra S , Sgaier S K , Thompson L , Moses S , Ramesh B M , Alary M , Blanchard J F 
Published: July 2011

BackgroundThere is substantial heterogeneity in the size and trajectory of HIV, driven largely by differences in the population sexual structure, which determines overall HIV transmission dynamics. Two standard methods have been developed to appraise epidemics and guide prevention strategies. The numerical proxy method classifies epidemics based on HIV prevalence thresholds. The Modes of Transmission (MOT) model estimates the distribution of incidence over 1 year among subgroups. Neither approach explicitly captures the drivers of the epidemic and can therefore lead to misguided prevention priorities. Using data from India, we explored the limitations of current methods and propose an alternative approach.MethodsWe compared outputs of the traditional methods in five countries with published results, and applied the numeric and MOT model to India, and to six districts within India. We developed an alternative approach based on a qualitative understanding of local epidemic drivers, the Transmission Dynamics Epidemic Classification (TDEC) scheme, and demonstrated its application. Where data permitted, we calculated the population attributable fraction of paid sex for HIV infection among males to assist in TDEC classification.ResultsCountry and district level analysis illustrated three main limitations of the numeric and MOT methods: (1) their results misinterpreted underlying transmission dynamics and were inconsistent; (2) they were difficult to apply to local epidemics with heterogeneity across districts ; and (3) the MOT model was highly sensitive to input parameters, many of which required extraction from non-regional sources. The TDEC method offered a logical algorithm to characterise local sexual structures that likely sustain onward HIV transmission; it required minimal but key input data.ConclusionTraditional appraisals of HIV epidemics can misdirect prevention programming if the goal is long-term HIV control. By characterising local transmission dynamics, the TDEC approach provides a potentially more effective tool with which policy makers can design intervention programs.
P1-S4.16 The UNAIDS modes of transmission model: a useful tool for decision making?
Authors: Foss A , Prudden H , Mehl A , Zimmerman C , Ashburn K , Trasi R , Kiess M , Bantebya-Kyomuhendo G , Fritz K , Watts C 
Published: July 2011

BackgroundThe UNAIDS Modes of Transmission (UNAIDSMoT) model is increasingly being used to inform national-level HIV priority setting. Although the model is simple to use, important factors may be omitted. Using the UNAIDSMoT model, with Uganda and Cambodia as case studies, we explored the influence of the incorporation of additional factors.MethodsA detailed review of the UNAIDSMoT model was conducted, including reviewing the model structure, data requirements, parameters and assumptions. Country-specific literature reviews were undertaken, along with field visits involving key-informant interviews, to identify the main features of the HIV epidemic in each setting. Adaptations were made to the UNAIDSMoT model to explore the sensitivity of the model projections to these revisions.ResultsA key limitation of the original UNAIDSMoT model is that it does not allow an individual's multiple sources of risk to be considered. The model was adapted to incorporate important multiple risk sources (including injecting drug use), and the effects of the 2008 change in Cambodian law on human trafficking which led to brothel closures, the migration of many sex workers into entertainment venues, and the discontinuation of numerous outreach and condom distribution programmes. As illustrated in Abstract P1-S4.16 figure 1, the revised model projects lower percentages of new HIV infections occurring among sex workers (2% vs 5%) and the regular female partners of men who buy sex (5% vs 48%) than the original model, primarily replaced with new infections occurring in the new groups: entertainment workers who sell sex (38%), and injecting drug users and their sexual partners (5%). In Uganda, the high prevalence of HIV infection among women means that the static model predicts men are more at risk of infection from their female partners than women are from their male partners. This fails to reflect the dynamic chain of HIV transmission.Abstract P1-S4.16 Figure 1Distribution of HIV incidence in original and revised UNAIDSMoT models.ConclusionsOur analysis highlights the limitations of the UNAIDSMoT model, and the potential dangers of over-interpretation of a relatively simplistic and static reflection of a dynamic HIV epidemic (and prevention priorities) at a particular time-point. It is important to regularly re-structure and re-parameterise models according to new data and changes in patterns of risk behaviours. Further research to test the validity, sensitivity and robustness of the UNAIDSMoT model projections in different epidemic settings is needed.
P1-S4.17 Interactive demonstration of a model to calculate costs and cost effectiveness of different strategies for chlamydia screening and partner notification
Authors: Turner K , Adams E , Grant A , Macleod J , Bell G , Clarke J , Horner P 
Published: July 2011

BackgroundWe have developed a model to calculate costs and cost effectiveness of different intervention strategies for chlamydia screening, which can be used by commissioners to evaluate and plan their local service provision. The model and an analysis of national data have been recently published in BMJ. Increasingly, financial constraints will mean that tools such as ours will be vital to provide value for money in healthcare.MethodWe will give a live demonstration of our spreadsheet model using the example from our recent study. We invite delegates to input their own data in real time to a laptop for comparison and testing against the national and international picture. We plan to promote this before the meeting.Main outcome measuresCost effectiveness of screening (as cost per individual tested, cost per positive diagnosis, total cost of screening, number screened, number infected, sex ratio of those tested and treated). We will show how to compare current programmes with a planned change eg, in screening coverage or partner notification efficacy.ResultsIn 2008−2009 screening was estimated to cost £46.3 m and £506 per infection treated. The model results suggest that increasing male screening coverage from 8% to 24% (to match female coverage) would cost an extra £22.9 m and increase the cost per infection treated to £528. Increasing partner notification efficacy from 0.4 to 0.8 partners per index case would cost an extra £3.3 m and reduce the cost per infection diagnosed to £449.ConclusionsThe results are broadly representative of the national picture, but further evaluation of the cost effectiveness of partner notification and screening is urgently needed. We encourage practitioners who want to test this tool in their own setting to contact us (katy.turner@bristol.ac.uk).BMJ2011; 342:c725010.1136/bmj.c7250.
P1-S4.18 Using mathematical modelling to investigate the role of the hidden “population of men who have sex with men (MSM) on the HIV epidemic in Southern India”
Authors: Prudden H , Foss A , Mitchell K , Pickles M , Phillips A , Ramesh B M , Washington R , Alary M , Lowndes C , Vickerman P 
Published: July 2011

BackgroundBiological and behavioural data for men who have sex with men (MSM) in Bangalore, Karnataka, India, have mainly been collected from sites where commercial sex is prevalent. Consequently, the survey data may fail to capture the behaviour of a larger lower-risk “hidden” MSM population. Mathematical modelling is used to explore the potential bias in the survey data and better quantify the characteristics of this hidden population.MethodsA dynamic model of HIV transmission among MSM was developed and parameterised using detailed data* from high risk MSM in urban Bangalore. The MSM were categorised into three subgroups: Kothi and Hijra(KH): who mostly take the receptive role in anal sex, Panthis and Bisexuals(PB) who are predominantly insertive partners and Double Deckers(DD) who take both roles. Due to the sampling methods used, it was thought the MSM survey data were more representative of KH and DD than PB, although the extent of this bias is unknown. Therefore, no fitting constraint was applied to the PB HIV prevalence and instead the model was used to explore what PB HIV prevalence values are projected if the model was only fit to the 95% CIs of the prevalence data for KH and DD. One million randomly sampled model simulations were undertaken to find model fits.ResultsAbstract P1-S4.18 figure 1 shows that, although the model can produce HIV prevalence estimates consistent with the survey estimates, overall the model projections suggest a lower PB HIV prevalence is more consistent with the survey estimates for KH and DD. In addition, 80% of the model fits to the KH and DD HIV prevalence data had a sampled frequency of sex acts for PB in the lower half of the uncertainty interval suggesting PB's sexual activity may be lower than the median reported in the MSM survey. As expected, an inverse relationship occurs between PB population size and their level of sexual activity, with the median PB population size being 55 400 (2.7% of the total urban male population) and varying between 28 000 and 73 000 (1.5 to 3.9% of the total urban male population) for the IQR of the model fits Conclusions: Survey data imply MSM are a small, highly active group, many of whom regularly sell sex, have very high numbers of partners and typically take the receptive role. As demonstrated here, modelling can be used to provide insights into the likely HIV prevalence, population size and sexual activity of hidden “MSM not reached in surveys.”Abstract P1-S4.18 Figure 1Number and range of projected HIV prevalence estimates for the PB population (from the model fits to KH and DD data. *Integratedbiological and behavioural assessment (IBBA) 2009, collected within the monitoring and evaluation of Avahan, the India AIDS initiative.
P1-S4.19 Stochastic network models
Authors: Noël P A , Allard A , Hébert-Dufresne L , Marceau V , Dubé L J. 
Published: July 2011

BackgroundWe present a general modelling scheme particularly adapted for the epidemiology of sexually transmitted infections. Emphasis is placed on the complex interaction structure of the population and on the probabilistic nature of the dynamics.MethodsWe represent the interaction structure of the population with complex network models. Markov Stochastic Processes are used to consider the probabilistic time evolution of both the network structure and the epidemiological state of the population. Idealised epidemiological problems are considered: they are qualitatively inspired by real-world systems but no actual real-world data is fed to the models. All analytical results are systematically validated through Monte Carlo numerical simulations.ResultsBy dedicating compartments to individuals with both similar epidemiological states and similar contact patterns, we observe great agreement between analytical results and Monte Carlo simulations see Abstract P1-S4.19 Figure 1. This is a special case of the general observation that compartmental models perform better when individuals within each compartment are very similar among themselves. Explicit examples are given for contact patterns changing through time as well as for the interactions of different infections in the same population.Abstract P1-S4.19 Figure 1Epidemiology on networks.ConclusionsBy specifying the structure of the population through its local features, we successfully model the probabilistic evolution of complex epidemiological systems. Infection stages and/or behavioural groups are considered the same way they are in “classical” compartmental models. The generality of the approach facilitates its application to a vast array of epidemiological phenomena.
P1-S1.17 HIV-1 molecular epidemiology in the Middle East and North Africa
Authors: Mumtaz G , Hilmi N , Akala F A , Semini I , Riedner G , Wilson D , Abu-Raddad L 
Published: July 2011

BackgroundHuman Immunodeficiency Virus Type I (HIV-1) is characterised by a high genetic variability. The distribution of HIV-1 subtypes in a population can help track transmission patterns and the evolution of the epidemic. The Middle East and North Africa (MENA) continues to be perceived as a region with limited HIV epidemiological data, but recent research indicates that nascent HIV epidemics appear to be emerging among high-risk groups including injecting drug users (IDUs), men who have sex with men (MSM), and female sex workers. The objective of this work was to review all evidence on HIV-1 subtype distribution in MENA where there remains several gaps in our understanding of the HIV epidemic.MethodsA comprehensive systematic review of all HIV-1 molecular epidemiology data in MENA was undertaken. Sources of data included (1) PubMed using a strategy with both free text and MeSH headings, (2) country-level reports and database including governmental and non-governmental organisations publications, and (3) international organisations reports and databases.ResultsIn several countries such as in Lebanon, Saudi Arabia, and Yemen, a very diverse distribution of HIV-1 subtypes was observed reflecting principally travel-related exogenous exposures. A trend of a dominant HIV-1 subtype was observed in few other settings and was often linked to HIV transmission within specific high-risk core groups such as subtype A and CRF35_AD among IDUs in Afghanistan, Iran, and Pakistan; and subtype C in heterosexual commercial sex networks in Djibouti and Somalia. Subtype B was predominant in Northern Algeria, Tunisia, and Morocco, but this appeared to reflect a mix of indigenous endemic transmission and exogenous exposures of West European and North American origin.ConclusionsMultiple introductions of HIV-1 variants due to exogenous exposures of nationals seemed common to all MENA countries, as observed from the high diversity in subtypes or the high genetic divergence among any specific subtype even if predominant. This is in part a reflection of the high population mobility in MENA. In several countries though, epidemic-type clustering of specific subtypes suggests established or nascent HIV epidemics among classical core risk groups for HIV infection. With overall weak surveillance systems in MENA, molecular investigations could help identify the emergence of hidden epidemics among high-risk groups. HIV prevention efforts in MENA must be prioritised for these groups.
P1-S4.26 Duration, incidence and prevalence ofChlamydia trachomatisin women: estimation by multi-parameter synthesis
Authors: Price M , Ades A E , De Angelis D , Welton N , Macleod J , Soldan K , Turner K , Simms I , Horner P 
Published: July 2011

BackgroundAn understanding of the prevalence and incidence ofChlamydia trachomatis(CT) infection is needed to assess the potential value of screening. Typically, the estimation of incidence, prevalence and duration are seen as distinct exercises. Here we estimate them simultaneously from the available data subject to the well-known relationship prevalence = incidence times duration.MethodsWe re-examine studies of duration of asymptomatic CT, based on recent reviews, and propose a model. Information from a recent synthesis of UK prevalence studies, and data on infection and re-infection rates in UK clinic settings, are used to generate estimates of incidence of infection in the general population, taking account of the effect of duration of infection on observed incidence. We use Bayesian multi-parameter evidence synthesis to check the consistency of the evidence and to produce internally coherent estimates of duration, incidence and prevalence in women.ResultsThe three sets of evidence sources that directly inform incidence, prevalence and duration respectively were consistent with each other. Our estimates are: duration of asymptomatic infection 1.25 years (1.04, 1.50), average incidence and prevalence in 16–44 year olds 2.2% (1.7, 2.9) per year and 2.1% (1.7, 2.6) respectively.ConclusionsThe apparently heterogeneous estimates of duration of asymptomatic CT in the literature are explained by the different study designs. Adapted appropriately, they agree with UK prevalence and incidence data.
P1-S4.27 Quality assurance of syphilis serological test in Guangdong, China, 2004–2009
Authors: Zheng H P , Wu X Z , Huang JinM 
Published: July 2011

BackgroundSyphilis has made a major comeback in China, now representing the most common communicable disease in many cities and regions. A total of 327 433 cases of syphilis were reported in 2009, accounting for a sevenfold increase since 1999. Accurate treponemal and non-treponemal serological testing are critical to providing a correct diagnosis, but there are substantial variations in the quality of serological diagnostic tests and testing across different parts of China. Since 2003, the Guangdong Provincial STI Control Center in collaboration with the Bureau of Public Health has developed a program on STIs laboratory construction and quality assurance system. We report the proficiency of serological test of syphilis among the STIs laboratories in Guangdong Province in 2004–2009.MethodsProficiency panels consisting of five samples with syphilis positive and negative sera were prepared in the provincial laboratory and sent to STIs laboratories for non-treponemal and treponemal testing once a year. Participating laboratories were asked to report the type of test used and quantitative and qualitative results for each serum. Each quantitative result was compared to the geometric mean of all participants' results, and was considered correct if it was less than fourfold difference from the mean titre.ResultsThe numbers of STIs laboratories in Guangdong which participated in the survey increased from 19 to 225 and a total of 13 203 sera were tested from 2004 to 2009. 98% laboratories used the “toluidine red unheated serum” (TRUST) as their non-treponemal test and all laboratories used the “Treponema pallidumparticle agglutination assay” (TPPA) as their treponemal test. The mean accuracies of non-treponemal tests among the laboratories evaluated increased significantly from 78.9% in 2004 to 97.7% in 2009 (χ2=17.11, p<0.01) for qualitative test results, and from 75.8% in 2004 to 90.8% in 2009 (χ2=8.09, p<0.01) for quantitative test results. Higher accuracies were observed with TPPA ranging from 93.5 to 100% (χ2=2.85, p>0.05) for qualitative test results and improved from 73.7% to 86.5% (χ2=4.7, p<0.05) for quantitative test results during this period. For non-treponemal testing, 4.1% (113/2754) of the results were found to be false negative and 2.3% (34/1456) were found to be false positive. For qualitative treponemal results, 6.5% (96/1470) and 1.9% (17/889) of treponemal results were found to be false-negative and false-positive respectively. For quantitative results, it was worth noting that in some cases, four to seven-titre deviations were observed for the same sera.ConclusionThis province-wide STIs laboratory construction and quality assurance system has helped to improve the accuracies of serological syphilis testing over time. But there is still room for improvement to facilitate improved control of syphilis in China.
P1-S4.29 Synthesis of evidence on implementation research on point-of-care syphilis tests: a systematic review
Authors: Jafari Y , Johri M , Ako-Arrey D , Shivkumar S , Lambert G , Claessens C , Klein M , Cajas J , Peeling R , Pai N 
Published: July 2011

BackgroundWith the increase in global prevalence of syphilis, synthesis of evidence of point-of-care (POC) assays is warranted. While a clear methodology exists to meta-analyse diagnostic performance, a clear rubric that incorporates implementation research outcomes (IRO) relevant for policy making is lacking. Recently, Grading of Recommendations Assessment, Development and Evaluation (GRADE) working group called for a shift to emphasis on patient-centred outcomes for making policy recommendations. However, a lack of clarity in defining, elucidating, and reporting of these outcomes prevents their utilisation in practice. Within this context, we reviewed global evidence on IROs for syphilis POC tests.MethodWe systematically searched nine electronic databases for the period of January 1980 to September 2010. Articles that addressed IRO regarding POC syphilis tests were reviewed and data extracted. A second reviewer independently reviewed a subset of the articles. Outcomes were synthesised into a narrative review.Results31 (48%) from 64 full text articles assessed were included in the narrative review. Twenty-four studies were cross-sectional, six were case-control, while one was a clustered randomised control trial (RCT). IROs were categorised into: Acceptability, Preference, Feasibility, Prevalence, Barriers and Challenges, and Economic Evaluations of POC tests. Three papers reported outcomes on acceptability, four on preference, ten on feasibility, seven on impact, six on prevalence, seven on barriers and challenges, and seven on economic evaluations. Overall, studies were concordant on findings of high acceptability and feasibility of POC tests as well as the testing strategy used. Preference was not well demonstrated in studies. Impact was particularly well demonstrated in antenatal clinic attendees by a clustered RCT. Barriers and challenges ranged from biotechnological limitations of the tests to lack of political will. Heterogeneous methodologies employed across studies to conduct economic evaluations made it difficult to draw conclusive statements.ConclusionsResults were generally in agreement across studies, yet unsystematic methods of collecting and recording outcomes made it difficult to statistically combine outcomes. Weaknesses in the reporting of IROs limit our ability to form comprehensive context-specific policies. Further efforts in establishing a framework for conducting implementation research is required.