Biostatistics
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Browsing Biostatistics by Author "Schall, R."
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Item Open Access Assessment of different methods of determining confidence intervals for the difference of binomial proportions(University of the Free State, 1998-05) Nel, Mariette; Joubert, G.; Schall, R.; Nel, D. G.Abstract not availableItem Open Access Profile of clinical trial biostatisticians and university courses to train them in South Africa(University of the Free State, 2003-11) Rossouw, Sharon Lynne; Joubert, G.; Schall, R.English: Many statistical issues in the area of clinical trials are specific to this particular field. A clinical trial biostatistician should not only be appropriately qualified in general statistical theory, but also be appropriately trained and experienced in the application of statistics to clinical trials. This thesis investigates the background and training of statisticians practicing in this field in South Africa. It provides an overview of the training that is available for clinical trial biostatisticians at universities in South Africa. Lastly, the thesis also provides recommendations for the training and development of clinical trial biostatisticians. The methodology used for this research included a literature study regarding the required profile (education/training, years of experience and part of the industry in which they are employed) of a clinical trial biostatistician, and topics of interest to such a biostatistician. A review of the content of statistics courses offered at South African Universities was performed. A questionnaire survey was conducted to assess the education/training profile of clinical trial biostatisticians in South Africa and to assess the knowledge of biostatisticians in areas considered necessary to be an appropriately qualified and experienced clinical trial biostatistician as defined in the literature. Twenty-nine respondents were considered valid clinical trial biostatisticians and were thus included in the analysis of the clinical trial biostatistician questionnaires. Twenty South African universities were approached to provide information regarding the statistics courses they present. Information was obtained from fourteen (70.0%) of these universities. The profile of clinical trial biostatisticians in South Africa, with respect to qualifications and experience, is comparable to clinical trial biostatisticians in Europe. However, the industries in which the biostatisticians are employed differ from those that employ clinical trial biostatisticians in Europe. South African clinical trial biostatisticians are not necessarily familiar with all the topics applicable to their discipline. The areas in which they were the least familiar were: regulatory requirements and international guidelines, statistical analysis considerations, reporting, and quality control and documentation. Aside from statistical methods which were mostly learned at university, knowledge and experience were mostly acquired through on-the-job training followed by self-study and reading. It is hoped that the implementation of a university programme specific to clinical trial biostatisticians, improvements in current statistical courses, the development of a clinical trial biostatistician manual and the introduction of a medical statistician certification scheme, would contribute to developing what Iman (1995) is referring to when he quotes Kettenring in saying, "Industry needs holistic statisticians who are nimble problem solvers".Item Open Access Randomised placebo-controlled trial to evaluate the effect of vitamin A on mother-to-child transmission of HIV-1 in Bloemfontein(University of the Free State, 2002-11) Chikobvu, Perpetual; Joubert, G.; Schall, R.; Van der Ryst, E.English: Mother-to-child (vertical) transmission is the primary means by which young children acquire human immunodeficiency virus type 1 (HIV -1) infection. Anti-retrovirals such as Zidovudine and nevirapine can reduce vertical transmission of HIV significantly, but this treatment is still largely unaffordable in Africa. Maternal vitamin A deficiency is suspected to enhance vertical transmission of HIV. Furthermore, vitamin A is known to act as a coenzyme to the immune process. Therefore, a double-blind randomized placebo controlled trial to assess the effect of vitamin A supplementation on vertical transmission of HIV was launched in Bloemfontein in 1997. A total of 2949 pregnant women attending the antenatal clinics at Pelonomi and Universitas hospitals and the Mangaung University Community Partnership clinic were counselled for HIV testing, and 2543 were willing to be screened by HIV testing for possible inclusion in the trial. Of the women screened 595 (23.4%) were HIV positive, and 303 of these were willing to participate in the trial. 152 women were randomized to vitamin A treatment and 151 to placebo treatment. Patients were seen at 2 monthly intervals in the antenatal phase. Post-natally mother-infants pairs were seen when the infant was 1 month old, 3 months old, and thereafter, 3 monthly till 18 months old. A total of 191 patients (63% of all the study participants) missed one or more visits and had to be traced. Of the 303 patients included in the study 158 had a conclusive infant HIV test result (patients in the Intention To Treat (!TT) analysis population) and 104 patients had a conclusive infant mv test result when the baby was 3 months old (patients in the Per Protocol (PP) analysis population). Of 158 patients, in the ITT population 73 were in the vitamin A group and 85 in the placebo group. Per treatment group the baseline characteristics of those in the IIT population and those who are not, did not differ significanti y. The mv transmission rates were 19.2% and 21.2% for vitamin A and placebo groups respectively (IIT population). There is no statistically significant difference in the transmission rates between vitamin A and placebo groups (p=0.76). Overall, this study provides no evidence that vitamin A is effective in reducing vertical mv-1 transmission rate. There was no statistically significant difference in the percentages of mv symptoms recorded at post delivery visit 1 through to the 18 months visit between the two treatment groups for either mothers or infants. A similar pattern was observed for the vital signs for the mothers. The full blood and T-cell counts were similar between the two treatment groups at all visits for both mothers and infants. Only 4 patients reported adverse events; these were not related to the treatment. Twenty six infants and one mother died during the study. The overall infant mortality rate was 85.8 per 1000 infant population. The infant death rates were approximately 11% in the placebo group and 6% in the vitamin A group (p=0.097). Thus, Vitamin A was associated with a reduction in infant mortality, although not statistically significant. This association may be worth further investigation as there is potential for a substantial impact.