Browsing by Author "Akyol, Mesut"

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    Plasma amino-terminal propeptide of C-type natriuretic peptide concentration in normal-weight and obese children
    (2017) Topçu, Seda; Akyol, Mesut; Orhon, Filiz Şimşek; Tıp Fakültesi; Özhan, Bayram; Alkan, Afra; Başkan, Sevgi; Ulukol, Betül
    Objective: In studies on the relationship between amino-terminal propeptide of C-type natriuretic peptide (NT-proCNP) concentration and height velocity in children, CNP has been implicated as an emerging new growth marker during childhood. It has been reported that besides its well-studied role in growth, plasma CNP levels are reduced in overweight and/or obese adolescents, suggesting CNP as a potential biomarker in childhood obesity. The primary goal of this study was to test this hypothesis in a Turkish population. Methods: Consent was taken from 317 children [ages 0-18 (158 girls, 159 boys)] and their parents. All subjects were physically examined; anthropometric measurements were obtained. Body mass index was calculated. During routine blood work, 1 mL extra blood was taken. Plasma NT-proCNP concentration was measured by enzyme-linked immunosorbent assay. Results: Results confirmed the previously described relationship between plasma NT-proCNP concentration and growth velocity. Plasma NT-proCNP concentration showed a negative correlation with age, weight, and height in children. Gender was not a factor that alters the age-dependent plasma NT-proCNP concentration until puberty. Conclusion: Unlike previous reports, plasma NT-proCNP concentration of overweight/obese children was not significantly lower than that of children with normal weight in age groups analyzed in a Turkish population. Thus, it is too early to conclude that CNP is a potential biomarker in childhood obesity. Further studies are necessary to address this question.
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    Yaşam çözümlemesine yeni bir yaklaşım: MARS
    (Sağlık Bilimleri Enstitüsü, 2011) Akyol, Mesut; Elhan, Atilla Halil; Biyoistatistik
    In this dissertation study it was investigated that whether Multivariate adaptive regression splines (MARS) can be used in survival analysis or not. In this context, MARS method was introduced briefly and its application to survival analysis was shown with its mathematical infrastructure.In order to adapt the MARS method to survival analysis, Martingale and Deviance residuals of Cox model does not use independent variable was investigated. Martingale and Deviance residuals were assumed as dependent variables of MARS method, so that it was tried to construct a model by using an independent variable which represents hazard and combines the censored variables.To show the applicability of MARS model, cancer data were used. In this carcinoma data set the variables having risk effect on variables was determined and the results obtained for different cut points for Platelet were used to improve the success of classical Cox-PH model.The method introduced in this thesis study was applied on UMARU-UIS data set which is frequently come across with the references related to survival analysis and it was shown that MARS model can provide more contributions to classical Cox-PH model.Key Words: Cox-PH model, Deviance residuals, MARS, Martingale residuals, Multivariate adaptive regression splines