K Marsh

Improvements in prevalence trend fitting and incidence estimation in EPP 2013.

Objective:Describe modifications to the latest version of the Joint United Nations Programme on AIDS (UNAIDS) Estimation and Projection Package component of Spectrum (EPP 2013) to improve prevalence fitting and incidence trend estimation in national epidemics and global estimates of HIV burden. Methods:Key changes made under the guidance of the UNAIDS Reference Group on Estimates, Modelling and Projections include: availability of a range of incidence calculation models and guidance for selecting a model; a shift to reporting the Bayesian median instead of the maximum likelihood estimate; procedures for comparison and validation against reported HIV and AIDS data; incorporation of national surveys as an integral part of the fitting and calibration procedure, allowing survey trends to inform the fit; improved antenatal clinic calibration procedures in countries without surveys; adjustment of national antiretroviral therapy reports used in the fitting to include only those aged 15–49 years; better estimates of mortality among people who inject drugs; and enhancements to speed fitting. Results:The revised models in EPP 2013 allow closer fits to observed prevalence trend data and reflect improving understanding of HIV epidemics and associated data. Conclusion:Spectrum and EPP continue to adapt to make better use of the existing data sources, incorporate new sources of information in their fitting and validation procedures, and correct for quantifiable biases in inputs as they are identified and understood. These adaptations provide countries with better calibrated estimates of incidence and prevalence, which increase epidemic understanding and provide a solid base for program and policy planning.

Trends and associations of Trichomonas vaginalis infection in men and women with genital discharge syndromes in Johannesburg, South Africa

Objectives To better understand the epidemiology of Trichomonas vaginalis infection, we investigated the association between T vaginalis and demographic, clinical, microbiological and behavioural characteristics of patients presenting with genital discharges to a primary healthcare clinic in Johannesburg, South Africa. Methods During six annual surveys (2007–2012), 1218 cases of male urethral discharge syndrome and 1232 cases of vaginal discharge syndrome were consecutively recruited. Diagnostic methods included nucleic acid amplification (Neisseria gonorrhoeae, Chlamydia trachomatis, T vaginalis and Mycoplasma genitalium), microscopy (bacterial vaginosis and Candida) and serology (Treponema pallidum, herpes simplex virus type 2 (HSV-2) and HIV). Logistic regression analyses and χ2 tests were used to identify predictors of T vaginalis infection. Results The prevalence of T vaginalis decreased from 2007 to 2012 (men from 13.4% to 4.8%; women from 33.8 to 23.1%). Overall, 74 (6.1%) men and 291 (23.6%) women were T vaginalis positive, with the highest prevalence in those aged ≥40 years (men 13.6%; women 30.9%). T vaginalis infection occurred more often in pregnant women (adjusted OR (aOR) 2.67; 95% CI 1.29 to 5.54) and in women with serological evidence of T pallidum (aOR 1.63; 95% CI 1.08 to 2.45) or HSV-2 infections (aOR 1.75; 95% CI 1.16 to 2.64). T vaginalis infection occurred less often in men with coexistent gonorrhoea (aOR 0.35; 95% CI 0.21 to 0.57) and in women with either bacterial vaginosis (aOR 0.60; 95% CI 0.44 to 0.82) or Candida morphotypes (OR 0.61; 95% CI 0.43 to 0.86). Conclusions Although the prevalence of T vaginalis infection has decreased over time, it remains an important cause of genital discharge in South Africa, particularly in older patients and pregnant women.

Trends in HIV prevalence among young people in generalised epidemics: implications for monitoring the HIV epidemic

Background Countries measure trends in HIV incidence to assess the impact of HIV prevention and treatment programmes. Most countries have approximated trends in HIV incidence through modelled estimates or through trends in HIV prevalence among young people (aged 15–24 years) assuming they have recently become sexually active and have thus only been recently exposed to HIV. Methods Trends in HIV incidence are described and results are compared using three proxy measures of incidence: HIV prevalence among young women attending antenatal clinics (ANCs) in 22 countries; HIV prevalence among young male and female nationally representative household survey respondents in 14 countries; and modelled estimates of adult (ages 15–49 years) HIV incidence in 26 countries. The significance of changes in prevalence among ANC attendees and young survey respondents is tested. Results Among 26 countries, 25 had evidence of some decline in HIV incidence and 15 showed statistically significant declines in either ANC data or survey data. Only in Mozambique did the direction of the trend in young ANC attendees differ from modelled adult incidence, and in Mali and Zambia trends among young men differed from trends in adult incidence. The magnitude of change differed by method. Conclusions Trends in HIV prevalence among young people show encouraging declines. Changes in fertility patterns, HIV-infected children surviving to adulthood, and participation bias could affect future proxy measures of incidence trends.

Assessing and adjusting for differences between HIV prevalence estimates derived from national population-based surveys and antenatal care surveillance, with applications for Spectrum 2013.

Objective(s):To assess differences between HIV prevalence estimates derived from national population surveys and antenatal care (ANC) surveillance sites and to improve the calibration of ANC-derived estimates in Spectrum 2013 to more appropriately account for differences between these data. Design:Retrospective analysis of national population survey and ANC surveillance data from 25 countries with generalized epidemics in sub-Saharan Africa and 8 countries with concentrated epidemics. Methods:Adult national population survey and ANC surveillance HIV prevalence estimates were compared for all available national population survey data points for the years 1999–2012. For sub-Saharan Africa, a mixed-effects linear regression model determined whether the relationship between national population and ANC estimates was constant across surveys. A new calibration method was developed to incorporate national population survey data directly into the likelihood for HIV prevalence in countries with generalized epidemics. Results were used to develop default rules for adjusting ANC data for countries with no national population surveys. Results:ANC surveillance data typically overestimate population prevalence, although a wide variation, particularly in rural areas, is observed across countries and survey years. The new calibration method yields similar point estimates to previous approaches, but leads to an average 44% increase in the width of 95% uncertainty intervals. Conclusion:Important biases remain in ANC surveillance data for HIV prevalence. The new approach to model-fitting in Spectrum 2013 more appropriately accounts for this bias when producing national estimates in countries with generalized epidemics. In countries with concentrated epidemics, local sex ratios should be used to calibrate ANC surveillance estimates.

Monitoring trends in HIV prevalence among young people, aged 15 to 24 years, in Manicaland, Zimbabwe

BackgroundIn June 2001, the United Nations General Assembly Special Session (UNGASS) set a target of reducing HIV prevalence among young women and men, aged 15 to 24 years, by 25% in the worst-affected countries by 2005, and by 25% globally by 2010. We assessed progress toward this target in Manicaland, Zimbabwe, using repeated household-based population serosurvey data. We also validated the representativeness of surveillance data from young pregnant women, aged 15 to 24 years, attending antenatal care (ANC) clinics, which UNAIDS recommends for monitoring population HIV prevalence trends in this age group. Changes in socio-demographic characteristics and reported sexual behaviour are investigated.MethodsProgress towards the UNGASS target was measured by calculating the proportional change in HIV prevalence among youth and young ANC attendees over three survey periods (round 1: 1998-2000; round 2: 2001-2003; and round 3: 2003-2005). The Z-score test was used to compare differences in trends between the two data sources. Characteristics of participants and trends in sexual risk behaviour were analyzed using Students and two-tailed Z-score tests.ResultsHIV prevalence among youth in the general population declined by 50.7% (from 12.2% to 6.0%) from round 1 to 3. Intermediary trends showed a large decline from round 1 to 2 of 60.9% (from 12.2% to 4.8%), offset by an increase from round 2 to 3 of 26.0% (from 4.8% to 6.0%). Among young ANC attendees, the proportional decline in prevalence of 43.5% (from 17.9% to 10.1%) was similar to that in the population (test for differences in trend: p value = 0.488) although ANC data significantly underestimated the population prevalence decline from round 1 to 2 (test for difference in trend: p value = 0.003) and underestimated the increase from round 2 to 3 (test for difference in trend: p value = 0.012). Reductions in risk behaviour between rounds 1 and 2 may have been responsible for general population prevalence declines.ConclusionsIn Manicaland, Zimbabwe, the 2005 UNGASS target to reduce HIV prevalence by 25% was achieved. However, most prevention gains occurred before 2003. ANC surveillance trends overall were an adequate indicator of trends in the population, although lags were observed. Behaviour data and socio-demographic characteristics of participants are needed to interpret ANC trends.

Statistical models for incorporating data from routine HIV testing of pregnant women at antenatal clinics into HIV/AIDS epidemic estimates

Objective: HIV prevalence data collected from routine HIV testing of pregnant women at antenatal clinics (ANC-RT) are potentially available from all facilities that offer testing services to pregnant women and can be used to improve estimates of national and subnational HIV prevalence trends. We develop methods to incorporate these new data source into the Joint United Nations Programme on AIDS Estimation and Projection Package in Spectrum 2017. Methods: We develop a new statistical model for incorporating ANC-RT HIV prevalence data, aggregated either to the health facility level (site-level) or regionally (census-level), to estimate HIV prevalence alongside existing sources of HIV prevalence data from ANC unlinked anonymous testing (ANC-UAT) and household-based national population surveys. Synthetic data are generated to understand how the availability of ANC-RT data affects the accuracy of various parameter estimates. Results: We estimate HIV prevalence and additional parameters using both ANC-RT and other existing data. Fitting HIV prevalence using synthetic data generally gives precise estimates of the underlying trend and other parameters. More years of ANC-RT data should improve prevalence estimates. More ANC-RT sites and continuation with existing ANC-UAT sites may improve the estimate of calibration between ANC-UAT and ANC-RT sites. Conclusion: We have proposed methods to incorporate ANC-RT data into Spectrum to obtain more precise estimates of prevalence and other measures of the epidemic. Many assumptions about the accuracy, consistency, and representativeness of ANC-RT prevalence underlie the use of these data for monitoring HIV epidemic trends and should be tested as more data become available from national ANC-RT programs.

Improvements in Spectrum's fit to program data tool

Objective: The Joint United Nations Program on HIV/AIDS–supported Spectrum software package (Glastonbury, Connecticut, USA) is used by most countries worldwide to monitor the HIV epidemic. In Spectrum, HIV incidence trends among adults (aged 15–49 years) are derived by either fitting to seroprevalence surveillance and survey data or generating curves consistent with program and vital registration data, such as historical trends in the number of newly diagnosed infections or people living with HIV and AIDS related deaths. This article describes development and application of the fit to program data (FPD) tool in Joint United Nations Program on HIV/AIDS’ 2016 estimates round. Methods: In the FPD tool, HIV incidence trends are described as a simple or double logistic function. Function parameters are estimated from historical program data on newly reported HIV cases, people living with HIV or AIDS-related deaths. Inputs can be adjusted for proportions undiagnosed or misclassified deaths. Maximum likelihood estimation or minimum chi-squared distance methods are used to identify the best fitting curve. Asymptotic properties of the estimators from these fits are used to estimate uncertainty. Results: The FPD tool was used to fit incidence for 62 countries in 2016. Maximum likelihood and minimum chi-squared distance methods gave similar results. A double logistic curve adequately described observed trends in all but four countries where a simple logistic curve performed better. Conclusion: Robust HIV-related program and vital registration data are routinely available in many middle-income and high-income countries, whereas HIV seroprevalence surveillance and survey data may be scarce. In these countries, the FPD tool offers a simpler, improved approach to estimating HIV incidence trends.

P3.091 Distribution and Risk Factors of Trichomonas Vaginalis Infection in England: An Epidemiological Study Using Electronic Health Records from Sexually Transmitted Infection Clinics

Background Little is known about the recent epidemiology and public health impact of Trichomonas vaginalis infection in England. We investigated the distribution and risk factors of this common sexually transmitted infection (STI)and assessed whether the potential burden of infection could warrant a review of existing screening guidelines. Methods We used data from the Genitourinary Medicine Clinic Activity Dataset (GUMCAD) over a three year period (2009–2011) to investigate the characteristics of patients diagnosed with T. vaginalis, and to describe the distribution of cases in England. Case records were linked within each GUM clinic using the local patient identifier. Socio-demographic and clinical risk factors associated with a diagnosis of T. vaginalis were explored using multivariable logistic regression. Results Rates of T. vaginalis infection were highest in London and the West Midlands. Risk of a T. vaginalis diagnosis was strongly associated with older age in comparison to those aged 20–24 years, non-white ethnicity, in particular black Caribbean (adjusted Odds Ratio [aOR] = 4.23, 95% CI 3.98–4.50 in women; aOR = 8.00, 95% CI 6.48–9.87 in men) and black ‘other’ (aOR = 4.13, 95% CI 3.80–4.49 in women; aOR = 5.75, 95% CI 4.22–7.83 in men) ethnic groups and birth in the Caribbean (aOR = 1.27, 95% CI 1.16–1.38 in women; aOR = 1.63, 95% CI 1.28–2.09 in men) compared to the UK. Current gonorrhoea (aOR = 3.66, 95% CI 3.30–4.05) or chlamydia (aOR = 1.58, 95% CI 1.49–1.68) infection was an important risk factor for a diagnosis of T. vaginalis in women. Conclusion This study has characterised important patient groups at risk of T. vaginalis infection and allowed identification of areas of higher prevalence. Our results suggest that further research is needed to identify the public health benefits and feasibility of changing clinic screening protocols among at risk groups in these areas.

P3.174 The Sexual Health of Male and Female Sex Workers Attending Genitourinary Medicine Clinics in England

Background Sex workers (SWs) are assumed to be at increased risk of sexually transmitted infections (STIs), but there are limited comparative data with other population groups. Previously, SW sexual health data were only available from special studies, but it is now gathered routinely as part of the Genitourinary Medicine Clinic Activity Dataset (GUMCAD), a national STI surveillance system. Methods Twelve months of GUMCAD data were analysed descriptively with the prevalence of STIs among SWs and other genitourinary (GUM) clinic attendees investigated. The increased risk of STI in SWs was estimated using logistic regression. Results In 2011, 3,192 SWs (2,704 females, 488 males) were recorded as making 10,481 visits to GUM clinics. These visits were reported from a minority of clinics (primarily large, specialist centres in London). SWs utilised a variety of services including sexual health screens, HIV tests and vaccination; however, a minority of SWs were not recorded as having STI/HIV tests. Disparities in sexual health were observed among SWs. Male SWs had worse sexual health outcomes than female SWs (e.g. period prevalence of gonorrhoea among those tested: 17.6% vs. 2.7%) and migrant female SWs had better outcomes than UK-born female SWs (e.g. period prevalence of chlamydia among those tested: 8.5% vs. 13.5%). SWs also had an increased risk of STI when compared with other attendees, with the greatest risks in male SWs (Chlamydia: ORadj:3.98, 95% CI: 3.05–5.18, p < 0.001). Conclusions Routinely-gathered GUMCAD data can be used to assess the sexual health of SWs in England. Disparities in sexual health and differences in service utilisation appear to exist between different groups of SWs. Some STIs are more prevalent among SWs than the general public. However, these results should be interpreted with caution as the identifying SW code is new and inconsistencies in the way SWs are identified were observed.

O5 Partner notification for gonorrhoea: analysis of outcomes using surveillance data

Background Partner notification (PN) is an essential component of STI control but can be difficult where index cases have multiple casual partners. Guidelines recommend that for gonorrhoea, a minimum of 0.4 contacts/case in large conurbations, and 0.6 contacts/case elsewhere, should be screened. We investigated the effectiveness of newly introduced surveillance codes for monitoring standards of PN in England. Objectives To investigate the relationship between PN ratios for gonorrhoea and patient socio-demographic characteristics. Methods Data on PN from the Genitourinary Medicine Clinic Activity Dataset (GUMCAD) were analysed. Results Reporting on PN began on a rolling basis in 207 GUM clinics during 2011. Provisional data on PN were available from 171 clinics reporting data covering 951 clinic months in total, during which there were 7423 cases and 2749 contacts. In this period, the overall PN ratio for gonorrhoea was 0.37 contacts/case. PN ratios were highest for clinics in non-urban areas (0.42 vs 0.36 in urban areas) but there was no difference between PN ratios in London and the rest of England. PN was most successful for female partners of heterosexual male index cases (0.44 contacts/case). Of those attending as a contact 26% (707/2749) tested positive for gonorrhoea; 31% of females, 22% of heterosexual males and 24% of MSM. Conclusions Provisional data suggest that, on average, contact to index case ratios for gonorrhoea are below recommended standards but these are likely to vary considerably by clinic. The high prevalence of gonorrhoea among contacts emphasises the importance of PN for case finding and reducing transmission. Further analysis to better understand the strengths and limitations of these data is warranted.