Browsing by Subject "R"

Now showing 1 - 5 of 5
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    Open Access
    A reproducible approach to equity backtesting
    (2019) Arbi, Riaz; Gebbie, Timothy
    Research findings relating to anomalous equity returns should ideally be repeatable by others. Usually, only a small subset of the decisions made in a particular backtest workflow are released, which limits reproducability. Data collection and cleaning, parameter setting, algorithm development and report generation are often done with manual point-and-click tools which do not log user actions. This problem is compounded by the fact that the trial-and-error approach of researchers increases the probability of backtest overfitting. Borrowing practices from the reproducible research community, we introduce a set of scripts that completely automate a portfolio-based, event-driven backtest. Based on free, open source tools, these scripts can completely capture the decisions made by a researcher, resulting in a distributable code package that allows easy reproduction of results.
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    Open Access
    Hepatitis C in HIV-infected individuals: a systematic review and meta-analysis of estimated prevalence in Africa
    (2016) Azevedo, Tiago Castro Lopes; Zwahlen, Marcel; Rauch, Andri; Egger, Matthias; Wandeler, Gilles
    Although hepatitis C virus (HCV) screening is recommended for all HIV-infected patients initiating antiretroviral therapy, data on epidemiologic characteristics of HCV infection in resource-limited settings are scarce.
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    Open Access
    Impact of immune reconstitution inflammatory syndrome on antiretroviral therapy adherence
    (2012) Nachega, Jean B; Morroni, Chelsea; Chaisson, Richard E; Goliath, Rene; Efron, Anne; Ram, Malathi; Maartens, Gary
    ObjectiveWe determined the impact of immune reconstitution inflammatory syndrome (IRIS) on antiretroviral therapy (ART) adherence in a cohort of 274 human immunodeficiency virus (HIV)-infected South African adults initiating ART.MethodsWe carried out a secondary analysis of data from a randomized controlled trial of partially supervised ART in Cape Town, South Africa. Monthly pill count adherence, viral suppression (HIV viral load < 50 c/mL), and IRIS events were documented. Poisson regression was used to identify variables associated with ART adherence below the median in the first 6 months of ART.ResultsWe enrolled 274 patients: 58% women, median age 34 years, median CD4 count 98 cells/μL, 46% World Health Organization clinical stage IV, and 40% on treatment for tuberculosis (TB). IRIS and TB-IRIS developed in 8.4% and 6.6% of patients, respectively. The median cumulative adherence at 6 months for those with an IRIS event vs no IRIS was 95.5% vs 98.2% (P = 0.04). Although not statistically significant, patients developing IRIS had a lower 6-month viral load suppression than those without IRIS (68% vs 80%, P = 0.32). ART adherence below the median of 98% was independently associated with alcohol abuse (relative risk [RR] 1.5; 95% confidence interval [CI] 1.2–1.9; P = 0.003) and IRIS events (RR 1.7; 95% CI 1.2–2.2; P = 0.001).ConclusionAlthough IRIS events were associated with slightly lower adherence rates, overall adherence to ART remained high in this study population. Concerns about IRIS should not deter clinicians from early ART initiation.
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    Open Access
    Moving towards universal coverage in South Africa? Lessons from a voluntary government insurance scheme
    (2013) Govender, Veloshnee; Chersich, Matthew F; Harris, Bronwyn; Alaba, Olufunke; Ataguba, John E; Nxumalo, Nonhlanhla; Goudge, Jane
    BackgroundIn 2005, the South African government introduced a voluntary, subsidised health insurance scheme for civil servants. In light of the global emphasis on universal coverage, empirical evidence is needed to understand the relationship between new health financing strategies and health care access thereby improving global understanding of these issues.ObjectivesThis study analysed coverage of the South African government health insurance scheme, the population groups with low uptake, and the individual-level factors, as well as characteristics of the scheme, that influenced enrolment.MethodsMulti-stage random sampling was used to select 1,329 civil servants from the health and education sectors in four of South Africa's nine provinces. They were interviewed to determine factors associated with enrolment in the scheme. The analysis included both descriptive statistics and multivariate logistic regression.ResultsNotwithstanding the availability of a non-contributory option within the insurance scheme and access to privately-provided primary care, a considerable portion of socio-economically vulnerable groups remained uninsured (57.7% of the lowest salary category). Non-insurance was highest among men, black African or coloured ethnic groups, less educated and lower-income employees, and those living in informal-housing. The relatively poor uptake of the contributory and non-contributory insurance options was mostly attributed to insufficient information, perceived administrative challenges of taking up membership, and payment costs.ConclusionBarriers to enrolment include insufficient information, unaffordability of payments and perceived administrative complexity. Achieving universal coverage requires good physical access to service providers and appropriate benefit options within pre-payment health financing mechanisms.
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    Pregabalin for the treatment of generalized anxiety disorder: an update
    (2013) Baldwin, David S; Ajel, Khalil; Masdrakis, Vasilios G; Nowak, Magda; Rafiq, Rizwan
    A previous review summarized what was then known about the potential role of pregabalin in the treatment of patients with generalized anxiety disorder (GAD): this review provides an update on its pharmacological properties and presumed mechanism of action, the liability for abuse, and efficacy and tolerability in patients with GAD. Pregabalin has a similar molecular structure to the inhibitory neurotransmitter gamma amino butyric acid (GABA) but its mechanism of action does not appear to be mediated through effects on GABA. Instead, its anxiolytic effects may arise through high-affinity binding to the alpha-2-delta sub-unit of the P/Q type voltage-gated calcium channel in “over-excited” presynaptic neurons, thereby reducing the release of excitatory neurotransmitters such as glutamate. The findings of randomized controlled trials and meta-analyses together indicate that pregabalin is efficacious in both acute treatment and relapse prevention in GAD, with some evidence of an early onset of effect, and broad efficacy in reducing the severity of psychological and physical symptoms of anxiety. It also has efficacy as an augmenting agent after non-response to antidepressant treatment in GAD. Continuing vigilance is needed in assessing its potential abuse liability but the tolerability profile of pregabalin may confer some advantages over other pharmacological treatments in the short term for treatment in patients with GAD.