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Author: search.filters.author.Cihan, Murat

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    Sample size, power and effect size revisited: simplified and practical approaches in pre-clinical, clinical and laboratory studies
    (CROATIAN SOC MEDICAL BIOCHEMISTRY \& LABORATORY MEDICINE, 2021-01-01) Serdar, Ceyhan Ceran; Cihan, Murat; Yucel, Dogan; Serdar, Muhittin A.
    Calculating the sample size in scientific studies is one of the critical issues as regards the scientific contribution of the study. The sample size critically affects the hypothesis and the study design, and there is no straightforward way of calculating the effective sample size for reaching an accurate conclusion. Use of a statistically incorrect sample size may lead to inadequate results in both clinical and laboratory studies as well as resulting in time loss, cost, and ethical problems. This review holds two main aims. The first aim is to explain the importance of sample size and its relationship to effect size (ES) and statistical significance. The second aim is to assist researchers planning to perform sample size estimations by suggesting and elucidating available alternative software, guidelines and references that will serve different scientific purposes.
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    Comparison of the modified polyacrylamide gradient gel electrophoresis and high-performance liquid chromatography methods in determining LDL size
    (WALTER DE GRUYTER GMBH, 2022-01-01) Cihan, Murat; Tsukamoto, Hideko; Serdar, Muhittin; Erbil, M. Kemal
    Objectives In this study, we aimed to compare modified Krauss polyacrylamide gradient gel electrophoresis (PAGGE) and high-performance liquid chromatography (HPLC) methods in classification, quantification, and separation of lipoproteins and determining low-density lipoprotein (LDL) size. Methods Blood specimens were obtained from eighty-seven volunteers. We measured LDL size using the PAGGE method and HPLC method with total cholesterol (TC) and triglyceride (TG) peaks. In the PAGGE method, Coomassie Brilliant Blue (CBB) staining was used instead of Sudan black staining, unlike the original method. The relationship between PAGGE and HPLC methods was evaluated by Pearson correlation test and Passing-Bablok regression analysis. Agreement between them was evaluated by Kappa analysis and Bland-Altman plots. Results Statistically significant correlation was found between the LDL size with PAGGE and HPLC methods under the cholesterol curve (HPLC-TC) (r=0.924, p<0.001). Similarly, there was a statistically significant correlation between PAGGE and HPLC methods under the TG curve (HPLC-TG) (r=0.910, p<0.001). In the PAGGE method, within-day precision was found as 2\% and between-day precision as 3\%. It was determined agreement between HPLC-TC vs. HPLC-TG methods and HPLC-TG vs. PAGGE methods was higher than HPLC-TC vs. PAGGE (Kappa values