Browse
Recent Submissions
Now showing 1 - 5 of 13
- ItemField evaluation of BD FACSPrest for haemoglobin and CD4 measurement(Scientific and Academic Publishing Co., 2017) Chaba, Linda; Kingwara, Leonard; Muriungi, HenryBackground:Measurements of CD4 and haemoglobin are used to determine the immunological state and information about disease progression for HIV-infected patients. Use of BD FACS Presto™ point of care (POC) device for CD4 and haemoglobin (Hb) determination can significantly improve access, uptake and coverage of laboratory services and hence management of HIV-infected patients in resource-limited settings. This study evaluated the relative bias in CD4 and Hb measurements using BD FACSPresto™ system compared to BD FACSCalibur™ CD4 analyser and Mindray BC-5380 haematology analyser respectively based on venous and capillary blood samples in a clinical hospital setting. Methods:Venous and capillary blood samples were used to determine CD4 counts and Hb levels among HIV-1 infected patients. The samples were analysed on the BD FACSPresto™ and results compared against BD FACSCalibur™ and Mindray BC-5380 for CD4 and haematology analyser respectively. Results: Results for absolute CD4 counts in both venous and capillary blood showed a high correlation (R2 = 0.922, P< 0.001) when they were analysed on BD FACSPresto™ and BD FACSCalibur™ machines. Overall, the mean difference in absolute CD4 count was 77.16 cells/mL (95%CI: 49.89, 104.42, p<0.01) when analysed on two platforms. The BD FACSCalibur™ gave a higher mean of absolute CD4 count (834.38 cells/ml) compared to BD FACSPresto™ (757.23 cells/ml) when venous sample type is used. There was a significant mean difference of Hb levels at 0.31 (P <0.001) between the two sample types when analysed on BD FACSPresto™ and Mindray BC-5380 haematology analyser. In addition, there was a high correlation (R2 = 0.920, P< 0.001) of Hb level measurements between the BD FACSPresto™ and Mindray BC-5380 haematology analyser.Conclusion: The BD FACSPresto performed satisfactorily in comparison to the conventional reference standard technologies. Venous and capillary blood sample types showed a high correlation when analysed for absolute CD4 count and Hb using BD FACSPresto™, BD FACSCalibur™ and Mindray BC-5380 haematology analyser. BD FACSPresto capillary platform can be used interchangeably with BD FACSCalibur™ venous platform for CD4 and Mindray BC-5380 for Hb measurement in resource limited settings to increase access and uptake of laboratory services.
- ItemUsing copulas to select prognostic genes in melanoma patients(Life science Global, 2017) Chaba, Linda; Odhiambo, John; Omolo, BernardMelanoma of the skin is the fifth and seventh most commonly diagnosed carcinoma in men and women, respectively, in the USA. So far, gene signatures prognostic for overall and distant metastasis-free survival, for example, have been promising in the identification of therapeutic targets for primary and metastatic melanoma. But most of these gene signatures have been selected using statistics that depend entirely on the parametric distributions of the data (e.g. t-statistics). In this study, we assessed the impact of relaxing the parametric assumptions on the power of the models used for gene selection. We developed a semi-parametric model for feature selection that does not depend on the distributions of the covariates. This copula-based model only assumed that the marginal distributions of the covariates are continuous. Simulations indicated that the copula-based model had reasonable power at various levels of the false discovery rate (FDR). These results were validated in a publicly-available melanoma dataset. Relaxing parametric assumptions on microarray data may yield procedures that have good power for differential gene expression analysis.
- ItemEvaluation of methods for gene selection in melanoma cell lines(Life science Global, 2016) Chaba, LindaA major objective in microarray experiments is to identify a panel of genes that are associated with a disease outcome or trait. Many statistical methods have been proposed for gene selection within the last fifteen years. While the comparison of some of these methods has been done, most of them concentrated on finding gene signatures based on two groups. This study evaluates four gene selection methods when the outcome of interested is continuous in nature. We provide a comparative review of four methods: the Statistical Analysis of Microarrays (SAM), the Linear Models for Microarray Analysis (LIMMA), the Lassoed Principal Components (LPC), and the Quantitative Trait Analysis (QTA). Comparison is based on the power to identify differentially expressed genes, the predictive ability of the genelists for a continuous outcome (G2 checkpoint function), and the prognostic properties of the genelists for distant metastasis-free survival. A simulated dataset and a publicly available melanoma cell lines dataset are used for simulations and validation, respectively. A primary melanoma dataset is used for assessment of prognosis. No common genes were found among the genelists from the four methods. While the SAM was generally the best in terms of power, the QTA genelist performed the best in the prediction of the G2 checkpoint function. Identification of genelists depends on the choice of the gene selection method. The QTA method would be preferred over the other approaches in predicting a quantitative outcome in melanoma research. We recommend the development of more robust statistical methods for differential gene expression analysis.
- ItemFitting a dynamic yield macro model in a frontier market: evidence from Kenya(Social Science Research Network, 2014-12-28) Akoth, Mercy; Othieno, Ferdinand O.We examine the dynamic interaction between macroeconomic factors and the unobserved yield curve factors in Kenya between 1 March 2011 and 31 March 2014. First we parametarise the yields only Term Structure Model using a Dynamic Nelson Siegel approach. We then characterise the dynamic interaction between the extracted unobserved yield curve latent factors and the observed macroeconomic factors, (inflation and CBR) using a Vector Autoregressive approach. We find that yield curve own dynamics account for the greatest percentage variation in the forecast error variance of the latent factors with the level factor accounting for a highly significant percentage of the one month forecast variance in its own dynamics and that of the slope and curvature factors, (100, 84 and 87 per cent respectively). The macro factors chosen on the other hand do not account for any of the variation in latent factors earlier during the forecast horizon though increases in their significance as the forecast horizon increases. We conclude that a large amount of idiosyncratic variation relate to the yield curve that is unrelated to observed macroeconomic factors in the short term with the observed macro factors becoming more influential as the forecast horizon increases.
- ItemImpacts of pension reforms on the Kenyan pension industry(2014-08) Masinde, Victoria; Olukuru, JohnThe emergence of full-fledged reforms in Kenya from the introduction of the Retirement Benefits Authority in1997 has rekindled hopes among the ageing population in Kenya. These reforms are geared towards creating good social welfare conditions for Kenyans. The Kenyan Pension industry remains a significant growth area which needs structural changes in management and governance in order to meet the ever changing scheme member needs. This is what forms the basis of the NSSF Act 2013. In this study the effect of the NSSF Act contribution rate has been examined through use a Contribution rate model. Additionally, Kenyans’ perception towards the yet to be implemented NSSF Act has been observed by use of questionnaire analysis. These reforms are directly linked to the general economic growth of the country. The study asserts that the set 6% contribution is sufficient to meet the welfare conditions of Kenyans. This has been supported by majority of the stakeholders (scheme members, administrators and fund managers among others) however; good implementation strategies need to be put in place in order for the public to realize the good effects of the same. This study therefore seeks to identify the main social welfare reforms put in place, as well as find out the effects and challenges towards implementation of these reforms on the performance of the industry with a critical theoretical look at the NSSF Act 2013.