bluuebunny/crossref_metadata_2025_split huggingface dataset:
P1-S4.21 Calibration of an individual-based model of STI transmission in Uganda: a novel ABC-Bayesian Emulation hybrid approach
Authors: Johnson H , Edmunds W John , White R 
Published: July 2011

IntroductionThe complexity of dynamic epidemic systems has led to the use of large-scale stochastic models for prediction purposes. However, methods for robustly calibrating and analysing these models can be prohibitively inefficient. We propose an algorithm for fitting complex models that incorporates elements of both Approximate Bayesian Computation (ABC) and Bayesian Emulation. ABC enables inference about model parameters without needing to calculate a likelihood function, by generating approximations from repeated model runs. However, each model run might take hours. Emulation methods are being developed in the fields of cosmology and meteorological modelling. The complex model function is summarised as an “emulator”: a stochastic function that represents global behaviour of the function as a linear regression model and local deviations from this behaviour as Gaussian processes. The emulator acts as a cheap proxy for the complex model, allowing both calibration and sensitivity analysis to be conducted in a fraction of the time.MethodsWe report the initial application of an emulation-based calibration algorithm to an individual-based stochastic model of STI transmission in Uganda. Starting with uninformative priors for 19 behavioural and biological input parameters, we “trained” an emulator with 200 sampled parameter sets and their corresponding model output (point estimates of HIV prevalence). Sampling a further 10 000 parameter sets from the priors, we used the emulator to make output predictions over a large area of input parameter space. Weighting each parameter set by goodness of fit to observed data, we identified promising areas of parameter space for complex model evaluation. A more accurate emulator was then trained, incorporating this additional complex model output. The process was repeated as in sequential ABC methods.ResultsThe use of emulators allowed evaluation of large areas of parameter space due to increased computational efficiency. Processing time for one prevalence point estimate was reduced from over 15 min on an HPC cluster to less than 0.1 s on a PC. Even the first two waves of such an algorithm provided helpful insight into the most influential parameters.ConclusionsThe development of an ABC—Bayesian Emulation hybrid approach to complex model calibration is promising. Emulators offer large advantages in computational efficiency. However, further research is needed regarding weighting, tolerance levels and covariance.
P1-S4.22 Impact of a hypothetical chlamydia vaccine on population prevalence: a mathematical Modelling Study
Authors: Heijne J , Althaus C , Herzog S , Low N 
Published: July 2011

BackgroundIt has not yet been possible to develop aChlamydia trachomatis(chlamydia) vaccine but research to achieve this continues. It is therefore important to evaluate the potential impact of different chlamydia vaccine strategies on population prevalence. The optimal strategy might differ depending on whether a vaccine prevents chlamydia infection, or prevents ascending infection to reduce the risk of long term complications. Here, we used a mathematical model to focus on vaccination strategies that aim to reduce population prevalence.MethodsWe developed a deterministic pair model of heterosexuals aged 15–39 years that incorporates the formation and dissolution of sexual partnerships. We used sexual behavioural data from UK population-based studies to inform the model. The model has a baseline chlamydia prevalence of 3%. In all strategies examined, vaccination was introduced before sexual debut. We investigated the impact on population prevalence of different types of vaccine coverage, vaccine efficacy and duration of protection. We also assumed different types of protection after vaccination. We started with full protection, but since animal models have shown that sterilising immunity is difficult to achieve we also investigated partial protection of the vaccine by assuming a decreased susceptibility to infection after vaccination or, when infected, a shorter duration of infection or a reduced transmission probability.ResultsThe impact of different vaccination strategies on chlamydia population prevalence depends on the characteristics of the vaccine. In the best case scenario, where the vaccine coverage and efficacy is 100% and duration of protection lifelong, it takes about 7 years to half the prevalence. With an average duration of protection of 10 years, a vaccine coverage or vaccine efficacy of around 70% or higher per year was needed to half the chlamydia prevalence in 10 years. For high vaccine coverage levels, the impact of vaccinating women alone on population prevalence was greater than vaccinating both men and women. The potential impact of a vaccine on chlamydia population prevalence was sensitive to the duration of protection of the vaccine and the vaccine efficacy.ConclusionThe model suggests that the impact of vaccination strategies on chlamydia prevalence highly depends on characteristics of future vaccines. Current efforts in vaccine development should be accompanied by mathematical models to investigate the optimal strategies.
P2-S9.01 The impact of customs and sexual practices on young Maasai women's ability to negotiate their sexual and reproductive health in relation to HIV and AIDS in Loitokitok, Kenya
Authors: Matogo J N 
Published: July 2011

This research investigated the ways in which Maasai culture, as practiced in a rural and relatively isolated area of Kenya, impacted upon the transmission of HIV/AIDS. The author focused her field research on women aged 16–25, and a range of cultural practices contributing to and influenced by gender roles in Maasai society. Local practice has been addressed and recommendations made in relation to the position of the Maasai community in the wider political economy and Kenya's ethnos cape.The study also investigated strategies the women considered appropriate, practical and effective to cope with these risks. The field study was conducted in the Loitokitok district of Kenya.MethodologyThe research is within a qualitative paradigm. Choice of methodology was mainly based on ethic consideration of research within cultural context of Maasai Indigenous people. Data was generated through use of focus group discussions, semi structured interviews and informal observation methods. An extensive review of the literature was also conducted. The influence of gender based customs and practices are highlighted in a number of scholarly works, Governmental and non-governmental documents with regard to women's vulnerability to Sexually Transmitted Infections (STIs).The researcher maintained an “insider-outsider” position and a participatory role in order to try to identify the current state of Maasai women's reproductive health at the grass roots level.FindingsResearch findings have found that there is a challenge in young pastoralist women's reproductive health autonomy. Their risk of STIs especially HIV infection is strongly determined by cultural and sexual practices that are gender related.Existing customs and practices tend to be more repressive to the women's autonomy in sexual health matters as men hold power in most important roles in society.ConclusionsThe study does not call for cultural change or reformation of traditional culture within the Maasai community; rather it appeals for transformation of customs and practices that cause harm on women's reproductive health. Valuable cultural practices and intentions that recognise women and celebrate their womanhood should be encouraged in a way that is not physically or psychologically daunting experience on their wellbeing.To this end, the understanding and knowledge of the Maasai worldview is critical to the intervention of Maasai women's reproductive health rights. A more cultural approach to Maasai women's reproductive health is suggested to be more effective. In relation to the adoption of STI prevention measures, Maasai culture plays a key role towards identification of preventive measures and strategies.
P3-S1.26 NovelChlamydia trachomatispoint of care rapid test shows disappointingly low clinical sensitivity in urogenital Chlamydia infections in Paramaribo, Suriname
Authors: van der Helm J , Sabajo L , Morré S , Grunberg A , Speksnijder A , de Vries H 
Published: July 2011

BackgroundAffordable and reliable point of care (POC) tests to diagnose urogenital chlamydia infections (POC-Ct) are needed, especially in resource limited settings. WHO has formulated standards that POC tests have to meet. One of those is that the test should be sensitive. Three POC-Ct tests currently on the market all showed poor sensitivity between 12% and 17% in a non-manufacturer sponsored clinical study (van Dommelen 2010). One POC-Ct test evaluated in a manufacturer-sponsored study claims over 80% sensitivity (Mahilum-Tapay 2007). We evaluated the performance of this POC-Ct in two outpatient clinics in Suriname, S.A.MethodsBetween July 2009 and February 2010 963 women were included in a high risk STI clinic (n=181) and a low risk birth control clinic (n=782) in Paramaribo, Suriname. Nurse collected vaginal swabs were obtained for the POC-Ct (Diagnostics for the Real World, LTD, Cambridge, UK) and control NAAT (APTIMA Combo 2, Gen-Probe, San Diego, USA) in a cross-over model. Swabs were processed according to the manufacturers instructions. POC-Ct was compared to NAAT and sensitivity, specificity, positive- and negative predictive value (PPV, NPV) were calculated. Quantitative Ct load was determined with a real-time PCR targeting the cryptic plasmid. Ct load was expressed as inclusion forming units (IFU) based on defined serial dilutions. An independent t-test was used to compare log-transformed Ct loads between true positive and false negative POC-Ct results.ResultsCt prevalence, determined by NAAT, was 23% at the high risk STI clinic and 9% at the low risk birth control clinic. Four samples were excluded due to discrepancy in POC-Ct result between two lab technicians (n=3) and failure of POC-Ct (n=1). Performance results of POC-Ct compared to NAAT are shown in Abstract P3-S1.26 table 1. Quantitative Ct bacterial load was 65 times higher when POC-Ct detected Ct infection (geometric mean 115 IFU) compared to loads that POC-Ct did not detect (geometric mean 1.8 IFU, p<0.001). Human DNA concentration did not differ between the true positive and false negative POC-Ct results (p=0.904). Sensitivity of POC-Ct in samples with low Ct load was 16%.Abstract P3-S1.26 Table 1Performance results of POC-Ct compared to NAATNAAT +NAAT −SensitivitySpecificityPPVNPVPOC-Ct +483041.7%97.6%61.5%92.4%POC-Ct −67814ConclusionThe sensitivity and to a lesser extend the PPV of the POC-Ct did not meet the expectations as described previously (83.5%). The POC-Ct missed samples with a low Ct load. With a sensitivity of 41.7% the Diagnostics of the Real World POC-Ct test does not meet the ASSURED criteria of a sensitive test formulated by the WHO.
P3-S1.35 Systemic and mucosal IgG and IgA antibody responses in genitalChlamydia trachomatisinfection
Authors: Wiggins R , Morris G , Habgood L , Lacey C 
Published: July 2011

BackgroundChlamydia trachomatis(CT) is the most common sexually transmitted infection in the UK. Screening and treatment programmes do not appear to have reduced the population levels of Chlamydia. Ideally a vaccine stimulating both humoural and T-cell responses against CT should be developed. We therefore wished to further study the humoural immune response to chlamydial infection both systemically and mucosally in the female genital tract in natural infection.MethodsCervical secretions (obtained with Weck-Cel spears, Medtronic) and serum from twenty-six women diagnosed chlamydia-positive were assessed for Chlamydia-specific IgA and IgG responses (Anilab systems, Finland) at baseline and at 4 months follow-up. Samples from thirty chlamydia-negative women were used as controls. The Mann–Whitney non-parametric test was used to compare groups.ResultsThere was a significant difference between CT+ve and CT−ve IgG in serum samples (IgG median absorbance values p=0.006, median CT-ve samples 0, +ve samples 0.255) and IgA serum values (p=0.005, CT+ve median 0.491, CT−ve 0.119). There was no significant difference between cervical IgG and IgA levels between CT+ve and CT−ve women (IgG median absorbance values, CT+ve samples 0.012, 0 CT−ve; IgA CT−ve 0.202, CT+ve, 0.032), although there was a trend towards raised cervical IgG in CT+ve samples (p=0.08). There was no significant difference between antibody levels at baseline and 4 months for the 10 CT+ve women who have returned so far.DiscussionOur data suggests that the local and systemic antibody responses to genital chlamydial infection are highly variable. No CT+ve samples studied display positive absorbance levels in all four tested parameters. However, serum IgG and IgA responses are significantly raised in CT+ve individuals, and these values remain high at 4 months follow-up. This is in contrast to local responses which are not significantly different between CT+ve and CT−ve individuals, although there is a trend towards raised cervical IgG in CT+ve samples. The results of this study so far indicate that local immune responses, in comparison to systemic responses, are not well-defined. This may have implications both for chlamydial vaccine development, and mucosal assessment of candidate vaccines.
P3-S1.40 Frequency and predictors of recommended gonorrhoea therapies in Washington State
Authors: Kerani R , Stenger M , Aubin M , Golden M 
Published: July 2011

BackgroundWashington State (WA) and CDC treatment guidelines recommend ceftriaxone (CFX) as the primary therapy for gonorrhoea (GC), and some evidence suggests that azithromycin (AZM) plus an oral cephalosporin is superior to an oral cephalosporin alone in the treatment of GC.MethodsWe used information from WA GC case report forms submitted July 2009–December 2010 to calculate the proportion of cases receiving different GC therapies. We used log regression to identify factors associated with recommended treatments.ResultsTreatment data were available for 3910 (96%) of 4066 reported GC cases; 2087 (53.4%) were treated with CFX, 931 (23.8%) with cefixime, (533) 13.6% with cefpodoxime, and 359 (9.2%) with another drug. Of 1464 persons receiving an oral cephalosporin, 507 (34.6%) also received AZM. Abstract P3-S1.40 table 1 displays the distribution of single and multidrug therapies for the three most common therapies observed. In a multivariate model, treatment with CFX was associated with male gender (prevalence ratio (PR): 1.23, 95% CI 1.14 to 1.32), Asian/Pacific Islander race (PR: 1.10, 95% CI 1.00 to 1.20) and other/multiple races (PR: 1.13, 95% CI 1.04 to 1.22) (vs White race). Compared to persons treated by private sector medical providers, CFX use was more common among persons treated in STD clinics (PR: 1.65, 95% CI 1.53 to 1.77), ER/urgent care clinics (PR: 1.37, 95% CI 1.25 to 1.50), other hospital settings (PR: 1.27, 95% CI 1.12 to 1.44), or community health centers (PR: 1.14, 95% CI 1.00 to 1.29), and less common among those treated in family planning clinics (PR: 0.38, 95% CI 0.30 to 0.47) and by other provider types (PR: 0.86, 95% CI 0.76 to 0.98). Among persons treated with oral cephalosprins, concurrent treatment with AZM was associated with male gender (PR: 1.71 95% CI 1.45 to 2.01), treatment in an STD clinic (PR: 1.64, 95% CI 1.41 to 1.91) or ER/urgent care clinic (PR: 1.28, 95% CI 1.03 to 1.58) vs by a private provider, having GC only (PR:3.88, 95% CI 2.84 to 5.28) (vs chlamydial coinfection), and Seattle residence (1.32, 95% CI 1.08 to 1.61).Abstract P3-S1.40 Table 1TotalSingle drug therapyWith AZMWith doxyclyclineWith another drugCeftriaxone2087773 (37.0%)1051 (50.4%)231 (11.1%)32 (1.5%)Cefixime931543 (58.3 %)334 (35.9%)50 (5.4%)4 (0.3%)Cefpodoxime533334 (62.6%)173 (32.5%)25 (4.7%)1 (0.2%)ConclusionsApproximately half of all persons with gonorrhoea in WA do not receive CFX and over 20% receive an oral cephalosporin alone, which is not recommended in WA guidelines. Efforts to increase CFX should focus on identifying and surmounting barriers to the use of CFX, particularly in places such as family planning clinics and other settings where use is now low.
P3-S2.05 Invasive obstetric procedures and cesarean sections in women with known herpes simplex virus (HSV) status during pregnancy
Authors: Moss N , Gardella C , Drolette L , Magaret A , Wald A 
Published: July 2011

BackgroundBreach of neonatal skin by obstetric procedures during delivery increases risk of neonatal herpes among infants of women with genital HSV infections. We hypothesised that knowledge of genital HSV infection by clinical history or antibody tests (GH/HSV-2) prior to delivery would result in reduced use of invasive obstetric procedures, and we explored whether use of invasive procedures in infected women on suppressive antiviral therapy was similar to use in women without infection.MethodsWe reviewed 750 consecutive deliveries at an academic medical center in 2006; routine prenatal testing included HSV-1 and HSV-2 serostatus. The primary outcome was a composite of invasive delivery procedures (fetal scalp electrodes, artificial rupture of membranes, intrauterine pressure catheter, vacuum extraction or forceps extraction) among women with vs without GH/HSV-2. Women with planned c-sections, multiple gestation pregnancy, or genital herpes lesions at term were excluded.Results453 women, including 35 with a history of genital herpes (24 with HSV-2, 11 with HSV-1) and 59 with HSV-2 antibody but no history of genital herpes, were included in the analysis. Of the 94 women with GH/HSV-2, 56 (59.6%) received suppressive antiviral therapy. Among the 38 women with GH/HSV-2 not on suppressive therapy, 15 (39.5%) had an invasive obstetric procedure at delivery compared with 204 (57%) of 359 women without GH/HSV-2 (OR=0.50; 95% CI: 0.25 to 0.98). In contrast, no difference in unplanned c-sections was observed by GH/HSV-2 status (29% vs 28%). Among the 56 women with GH/HSV-2 treated with antiviral therapy, the risk of invasive procedures was similar to that of women without GH/HSV-2, 62.5% vs 57% (OR=1.27; 95% CI 0.71 to 2.26).ConclusionWomen with known genital herpes or HSV-2 positivity are less likely to undergo invasive procedures that increase the risk of neonatal herpes. However, obstetricians do not appear to avoid these procedures in women who are on suppressive therapy. These data suggest physicians who know their patients' HSV-2 status in pregnancy alter their behaviour to maintain the integrity of neonatal skin. Given the frequency of breakthrough HSV-2 shedding on suppressive antiviral therapy, and the occurrence of neonatal herpes in infants born to women on suppressive therapy, the high frequency of invasive procedure use among women on antiviral therapy is concerning.
P3-S3.04 Clinical screening of sexually transmitted infections and risk factors among people living with HIV at the University Hospital of Cotonou
Authors: Ahouada C , Bashi J , Zannou M D , Gougounon A , Akakpo J , Zinsou R , d'Almeida C , Ahomadegbe C , Azon-kouanou A , Ade G , Houngbe F 
Published: July 2011

BackgroundMany studies have shown an association between the presence of a sexually transmitted infection (STI) and the occurrence of HIV infection. Because of improved prognosis and quality of life due to antiretroviral (ARV), people living with HIV (PLHIV) tend to abandon safer sex practices. The consequence could be the resurgence of sexually transmitted infections. The objective of this study is to determine the prevalence of STIs and associated factors in the population of PLHIV in order to lay appropriate prevention strategies.MethodsThis is a descriptive cross-sectional study conducted from January to February 2011 on PLHIV admitted in consultation at Centre de Traitement ambulatoire, of academic Hospital of Cotonou. An interrogation and urogenital examination were realised systematically by physicians in all patients. STI diagnosis was presumptive, based on observed lesions. The dependent variable studied is the presence of suggestive lesions of STIs. The data entry was made using Epi Data 3.1 and statistical analysis with SAS version 9.2. Proportions were compared using the χ2test. The significance level was 5% and CIs at 95%.Results85 patients were recruited, 27 (31.76%) had suggestive lesions of STIs. The STIs lesions found in genitals were: irritation (21.18%), papular lesions (12.94%), discharge (10.59%), ulcers (9.41%), and malodorous vaginal discharge (4.71 %). The presumptive diagnosis raised in front of these lesions were: genital candidiasis (23.53%), genital herpes (8.24%), condyloma (3.53%), Chlamydia (2.35%), syphilis (1.18%). STI prevalence was 25% in patients on ARVs as against 52% among untreated OR 0.30 [0.10 to 0.84], p=0.02. The median CD4 count at diagnosis was 379 cells/μl. The majority of patients, that to say 58%, continues to maintain unprotected sex. They were 24% reported having procreated after knowledge of their positive HIV status. This indicates a risk of sexual transmission of infections.ConclusionSTIs are frequent in people with HIV even in patients treated with ARVs. Risk behaviours of STIs and HIV transmission are particularly observed in patients whose clinical and immunological status become satisfying. It appears important to emphasise the observance of security measures in monitoring of patients with HIV, especially when their clinical and immunological status are being improved.
P3-S3.08 Sensitivity and specificity of rapid HIV testing in a community setting
Authors: Trottier B , Nguyen V K , Thomas R , Machouf N , Vezina S , O'Brien R , Lavoie S , Longpré D , Boissonnault M , Charest L 
Published: July 2011

BackgroundIt was estimated in 2005 that 13% of men who have sex with men (MSM) in Montréal were HIV-positive, and that 23% of these were not aware of their diagnosis. Clinique l'Actuel introduced a pilot rapid HIV testing program using the MedMira kit in 2008. The objective of this study was to describe the sensitivity and specificity of rapid HIV tests in a community based, high HIV risk setting.MethodsAn advertising campaign encouraged MSM and others at risk for HIV to undergo testing through dedicated clinics offering rapid HIV tests. Patients calling for testing deemed at high risk were given appointments within 2 weeks, where they filled out a short questionnaire, received medical consultation routine STI screening, pre- and post- test counselling and their HIV test results within the hour. Those consenting received with a MedMira or and INSTI rapid test and regular HIV screening. Any positive result was confirmed by Western blot.Results2500 individuals were tested: 98% men with a median age of 34 (IQR: 26–41). For the MedMira test there were 43 true positives, 2295 true negatives, 13 false positives and four false negatives. 145 patients received the finger-prick INSTI test giving two true positives and 143 true negatives. For MedMira, sensitivity was 91.5% and specificity 99.5% while both figures were 100% for INSTI. The four false negatives were also negative by standard ELISA but positive for P24 antigen. Patients testing positive for HIV had significantly more history of previous STI than those testing negative (p=0.041).ConclusionIn this setting sensitivity and specificity of the rapid tests used was comparable to standard testing. Acute seroconversion likely explains the four false negatives. As with conventional testing, rapid testing requires adequate counselling about the possibilities of a false negative test. In high-risk populations, routine STI screening should always be performed together with HIV screening.