Browsing by Author "Chibawara, Trust"

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    Effects of antiretroviral therapy in HIV-positive adults on new HIV infections among young women : a systematic review protocol
    (BMC, 2019-03-05) Chibawara, Trust; Mbuagbaw, Lawrence; Kitenge, Marcel; Nyasulu, Peter S.
    Background: The HIV/AIDS pandemic has struck regions, countries, and populations in different ways. With the introduction of antiretroviral drugs, people living with HIV (PLHIV) have a much better prognosis, even though there are still many new infections in young women. The role of widespread antiretroviral therapy (ART) on the incidence of HIV in young women is unknown. Methods: We will conduct a comprehensive search of MEDLINE (PubMed), Excerpta Medica database (EMBASE), Scopus, Google Scholar, Cochrane Central Register of Controlled Trials (CENTRAL), World Health Organization’s (WHO’s) library database, Latin American and Caribbean Health Sciences Literature (LILACS), conference abstracts, and gray literature sources to identify any relevant literature. We will include randomized and non-randomized clinical trials and cohort studies in which ART was offered to adults aged 18 and above reporting outcomes in females aged 15 to 24 years. The outcomes of interest are HIV incidence, ART initiation, adherence, retention, and viral load suppression. We will screen titles, abstracts, and the full texts of relevant articles in duplicate. Disagreements will be resolved by consensus. We will extract data on the risk of HIV infection in younger females after the use of ART in the adult population. Discussion: To our knowledge, this is the first systematic review to look at the impact of ART use among adults on HIV incidence in young women. The results of this review will be used in a modeling study to simulate the effects of using ART as an effective tool to prevent sexual transmission of HIV to young women. Our findings will inform the treatment-as-prevention (TasP) strategy to reduce new HIV infections among young women.
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    Interpreting HIV diagnostic histories into infection time estimates : analytical framework and online tool
    (BMC (part of Springer Nature), 2019-10-26) Grebe, Eduard; Facente, Shelley N.; Bingham, Jeremy; Pilcher, Christopher D.; Powrie, Andrew; Gerber, Jarryd; Priede, Gareth; Chibawara, Trust; Busch, Michael P.; Murphy, Gary; Kassanjee, Reshma; Welte, Alex
    Background: It is frequently of epidemiological and/or clinical interest to estimate the date of HIV infection or time-since-infection of individuals. Yet, for over 15 years, the only widely-referenced infection dating algorithm that utilises diagnostic testing data to estimate time-since-infection has been the ‘Fiebig staging’ system. This defines a number of stages of early HIV infection through various standard combinations of contemporaneous discordant diagnostic results using tests of different sensitivity. To develop a new, more nuanced infection dating algorithm, we generalised the Fiebig approach to accommodate positive and negative diagnostic results generated on the same or different dates, and arbitrary current or future tests – as long as the test sensitivity is known. For this purpose, test sensitivity is the probability of a positive result as a function of time since infection. Methods: The present work outlines the analytical framework for infection date estimation using subject-level diagnostic testing histories, and data on test sensitivity. We introduce a publicly-available online HIV infection dating tool that implements this estimation method, bringing together 1) curatorship of HIV test performance data, and 2) infection date estimation functionality, to calculate plausible intervals within which infection likely became detectable for each individual. The midpoints of these intervals are interpreted as infection time ‘point estimates’ and referred to as Estimated Dates of Detectable Infection (EDDIs). The tool is designed for easy bulk processing of information (as may be appropriate for research studies) but can also be used for individual patients (such as in clinical practice). Results: In many settings, including most research studies, detailed diagnostic testing data are routinely recorded, and can provide reasonably precise estimates of the timing of HIV infection. We present a simple logic to the interpretation of diagnostic testing histories into infection time estimates, either as a point estimate (EDDI) or an interval (earliest plausible to latest plausible dates of detectable infection), along with a publicly-accessible online tool that supports wide application of this logic. Conclusions: This tool, available at https://tools.incidence-estimation.org/idt/, is readily updatable as test technology evolves, given the simple architecture of the system and its nature as an open source project.
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    Model-based inference on the impact of early access to antiretroviral therapy to all on HIV incidence among adolescent girls and young women in Eswatini
    (Stellenbosch : Stellenbosch University, 2021-04) Chibawara, Trust; Nyasulu, Peter; Kajungu, Dan; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Global Health. Epidemiology and Biostatistics.
    ENGLISH SUMMARY: Introduction: The introduction of antiretroviral drugs has enabled people living with HIV (PLHIV) to have a much better prognosis. As such, the use of antiretroviral drugs has resulted in the decline of global HIV incidence over the last decade. Whilst this achievement is important, the role of the widespread use of antiretroviral drugs on the HIV epidemic among adolescent girls and young women is still unknown. This study aimed to evaluate the impact of Early Access for all HIV-positive Adults to Antiretroviral (EAAA) on HIV incidence among adolescent girls and young women in Eswatini. Methods: To accomplish our research objectives, this research provided elaborate mathematical concepts that are multidisciplinary in nature and included evidence based systematic review, statistics, data science and public health approaches. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines was used for the systematic review. Using Simpact, an individual-based, event-driven, stochastic simulation tool, a specially designed HIV transmission model was adopted to simulate the heterosexual transmission of HIV in Eswatini. The application of a simplified model calibration approach combined clinical, biological, and behavioural indicators from the Eswatini implementation study called “Maximizing Antiretroviral Treatment for Better Health and Zero New HIV Infection: Early Access to Antiretroviral Treatment for All (MaxART EAAA)” and Eswatini demographic summary statistics to infer the impact of EAAA on HIV incidence in adolescent girls and young women. Results: The results of the systematic review showed that globally, there was no published or unpublished research found on the impact of the use of ART by HIV positive adults on HIV incidence in adolescent girls and young women. While on the other hand, our model which aimed to evaluate the impact of EAAA on older men aged 18 years and above in Eswatini showed a 45% (95% Confidence interval (CI): 37-55) reduction on HIV incidence among the adolescent girls and young women aged 15-24-years-old as opposed to CD4 cell count threshold for ART eligibility (Standard of care). Furthermore, simulated data showed that early access to ART has a similar impact of 47% (95% CI: 33-59) reduction in HIV incidence among adolescent boys and young men of the same age group. Conclusion: This study has demonstrated the impact of EAAA as a strategy to reduce new HIV infections among adolescent girls and young women aged between 15-24-years-old in the Eswatini population. These findings reinforce the need to adopt provisions for early initiation of ART treatment among HIV infected adults as a catalyst to minimize transmission of HIV to the adolescent population. Data from this study also highlight the need for other countries in the region who are faced with similar challenges of harbouring a high HIV prevalence to adopt EAAA as it has shown to be an effective approach to reduce HIV/AIDS incidence in the population. While these benefits are applaudable, we do recognize that HIV/AIDS treatment on its on is not sufficient; therefore, behavioural changes that guard against age-disparate relationships should be reinforced.
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    Pricing and hedging asian options using Monte Carlo and integral transform techniques
    (Stellenbosch : University of Stellenbosch, 2010-03) Chibawara, Trust; Ouwehand, P. W.; University of Stellenbosch. Faculty of Science. Dept. of Mathematical Sciences.
    ENGLISH ABSTRACT: In this thesis, we discuss and apply the Monte Carlo and integral transform methods in pricing options. These methods have proved to be very e ective in the valuation of options especially when acceleration techniques are introduced. By rst pricing European call options we have motivated the use of these methods in pricing arithmetic Asian options which have proved to be di cult to price and hedge under the Black􀀀Scholes framework. The arithmetic average of the prices in this framework, is a sum of correlated lognormal distributions whose distribution does not admit a simple analytic expression. However, many approaches have been reported in the academic literature for pricing these options. We provide a hedging strategy by manipulating the results by Geman and Yor [42] for continuous xed strike arithmetic Asian call options. We then derive a double Laplace transform formula for pricing continuous Asian call options following the approach by Fu et al. [39]. By applying the multi-Laguerre and iterated Talbot inversion techniques for Laplace transforms to the resulting pricing formula we obtain the option prices. Finally, we discuss the shortcomings of using the Laplace transform in pricing options.