• 대한예방의학회:학술대회논문집
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• 1994.02b
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• pp.270-284
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• 1994

Interim analyses of randomized trials enable investigators to make more efficient use of limited research resources and to satisfy ethical requirements that a regimen be discontinued as soon as it has been established to have an inferior efficacy/toxicity profile. Unfortunately. the integrity and credibility of these trials can be compromised if inappropriate procedures are used in monitoring interim data. 'In this paper we discuss how group sequential designs provide useful guidelines that enable one to satisfy the valid objectives of interim monitoring while avoiding undesirable consequences, and we consider how flexible one can be in the way such designs are implemented. We also provide motivation for the role of data-monitoring committees in preserving study integrity and credibility in either government- or industry-sponsored trials. In our view. these committees should have multidisciplinary representation and membership limited to individuals free of apparent significant conflict of interest, and ideally should be the only individuals to whom the data analysis center provides interim results on relative efficacy of treatment regimens. Finally. we discuss some important practical issues such as estimation following group sequential testing, anal ysis of secondary outcomes after using a group sequential design applied to a primary outcome, early stopping of negative trials. and the role of administrative analyses.

• The Korean Journal of Applied Statistics
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• v.20 no.3
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• pp.515-530
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• 2007

Stratum-specific likelihood ratio, which is ratio of the sensitivity to 1-the specificity in each stratum of the test, could be biased if the sensitivity and specificity of diagnostic test are affected by verification bias. Therefore, the optimal cutoff point determined by biased stratum-specific likelihood ratios is incorrect. In this study, we derived adjusted stratum-specific likelihood ratios using the adjusted sensitivity and specificity, and obtained the adjusted optimal cutoff point. The influence of the verification bias on the optimal cutoff point was described through the relation between adjusted and unadjusted stratum-specific likelihood ratios.

• Neonatal Medicine
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• v.28 no.1
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• pp.7-13
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• 2021

Purpose: To evaluate the risk factors and effects of fluctuations in oxygen saturation on the occurrence and severity of retinopathy of prematurity (ROP). Methods: From January 1, 2013 to January 31, 2020, 260 patients hospitalized in the neonatal intensive care unit of Ajou University Hospital were retrospectively analyzed. Results: Sixty-six patients (25%) were diagnosed with ROP; of them 39 required treatment. In the multivariate regression analysis of ROP severity, the odds ratio (OR) of gestational age was 0.32 (95% confidence interval [CI], 0.22 to 0.47; P<0.0001). The OR of saturation of peripheral oxygen (SpO₂) fluctuations at the 4th week after birth was 1.02 (95% CI, 1.02 to 1.12; P=0.041). Conclusion: SpO₂ fluctuations in premature infants younger than 30 weeks' gestational age affects ROP severity, especially at the 4th week of life.

• Communications for Statistical Applications and Methods
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• v.27 no.6
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• pp.603-624
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• 2020

There is an emerging interest in brain functional connectivity (FC) based on functional Magnetic Resonance Imaging in Alzheimer's disease (AD) studies. The complex and high-dimensional structure of FC makes it challenging to explore the association between altered connectivity and AD susceptibility. We develop a pipeline to refine FC as proper covariates in a penalized logistic regression model and classify normal and AD susceptible groups. Three different quantification methods are proposed for FC refinement. One of the methods is dimension reduction based on common component analysis (CCA), which is employed to address the limitations of the other methods. We applied the proposed pipeline to the Alzheimer's Disease Neuroimaging Initiative (ADNI) data and deduced pathogenic FC biomarkers associated with AD susceptibility. The refined FC biomarkers were related to brain regions for cognition, stimuli processing, and sensorimotor skills. We also demonstrated that a model using CCA performed better than others in terms of classification performance and goodness-of-fit.

• Genomics & Informatics
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• v.21 no.3
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• pp.28.1-28.13
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• 2023

Mild cognitive impairment (MCI) is a clinical syndrome characterized by the onset and evolution of cognitive impairments, often considered a transitional stage to Alzheimer's disease (AD). The genetic traits of MCI patients who experience a rapid progression to AD can enhance early diagnosis capabilities and facilitate drug discovery for AD. While a genome-wide association study (GWAS) is a standard tool for identifying single nucleotide polymorphisms (SNPs) related to a disease, it fails to detect SNPs with small effect sizes due to stringent control for multiple testing. Additionally, the method does not consider the group structures of SNPs, such as genes or linkage disequilibrium blocks, which can provide valuable insights into the genetic architecture. To address the limitations, we propose a Bayesian bi-level variable selection method that detects SNPs associated with time of conversion from MCI to AD. Our approach integrates group inclusion indicators into an accelerated failure time model to identify important SNP groups. Additionally, we employ data augmentation techniques to impute censored time values using a predictive posterior. We adapt Dirichlet-Laplace shrinkage priors to incorporate the group structure for SNP-level variable selection. In the simulation study, our method outperformed other competing methods regarding variable selection. The analysis of Alzheimer's Disease Neuroimaging Initiative (ADNI) data revealed several genes directly or indirectly related to AD, whereas a classical GWAS did not identify any significant SNPs.

• Dementia and Neurocognitive Disorders
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• v.21 no.1
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• pp.1-16
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• 2022

Background and purpose: We investigated existing nonpharmacological programs for people with dementia (PWD) to explore critical factors related to the effectiveness of these types of programs. Methods: We conducted a qualitative systematic literature review to identify nonpharmacological intervention programs developed for PWD and reviewed 36 randomized controlled trials. Among several outcomes reported in each study, we focused on the most common outcomes including quality of life (QoL), neuropsychiatric symptoms, depression, agitation, and cognition for further review. Results: Several factors were identified that might affect the outcomes of nonpharmacological interventions for PWD including study design, characteristics of the intervention, maintaining research participants, heterogeneity issues, and implementation fidelity. About half of studies in this review reported positive program effects on their targeted outcomes such as Well-being and Health for PWD on improving quality of life, neuropsychiatric symptoms and agitation; cognitive stimulation therapy on QoL, neuropsychiatric symptoms and cognition; and a stepwise multicomponent intervention on neuropsychiatric symptoms, depression and agitation. Conclusions: We found some programs even with a rigorous study design did not produce expected outcomes while other programs with poor designs reported positive outcomes, which necessitates further investigation on the validity of the assessments. Factors such as individual tailored and customized interventions, promoting social interactions, ease of administration and compatibility of interventions, and developing program theory need to be considered when developing nonpharmacological intervention programs.

• Journal of the korean academy of Pediatric Dentistry
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• v.51 no.3
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• pp.265-278
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• 2024

This study investigates the potential of cone-beam computed tomography (CBCT)-generated cephalograms as a replacement for conventional lateral cephalograms (LCs) in children and adolescents. This retrospective study included 60 individuals, equally divided into permanent and mixed dentition groups. Both groups underwent conventional LCs and CBCT scans on the same day. LCs were then derived from CBCT scans. The same examiner performed digital measurements twice, with a week's interval, identifying landmarks and obtaining 7 angular and 5 linear measurements. In the permanent dentition group, significant differences were observed between the two imaging modalities for 6 angular and 2 linear measurements. In the mixed dentition group, significant differences were observed for 3 angular and 2 linear measurements. However, none of these differences exceeded the clinically acceptable limit of 2.0° or 2.0 mm. No significant differences in any measurement were found between the two groups (p < 0.05). CBCT-generated LCs demonstrated comparable results with good reliability in both dentition groups, suggesting their potential as suitable alternatives for children and adolescents who require CBCT for clinical purposes.

• The Korean Journal of Applied Statistics
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• v.22 no.2
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• pp.329-340
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• 2009

For complex diseases such as diabetes, hypertension, it is believed that model-free methods might work better because they do not require a precise knowledge of the mode of inheritance controlling the disease trait. This is done by estimating the sharing probabilities that a pair shares zero, one, or two alleles identical by descent(IBD) and has some specific branches of test procedure, i.e., the mean test, the proportion test, and the minmax test. Among them, the minmax test is known to be more robust than others regardless of genetic mode of inheritance in current use. In this study, we compared the power of the methods which are based on minmax test and considering weighting schemes for sib-pairs to analyze sibship data. In simulation result, we found that the method based on Suarez' was more powerful than any others without respect to marker allele frequency, genetic mode of inheritance, sibship size. Also, The power of both Suarez- and Hodge-based methods was higher when marker allele frequency and sibship size were higher, and this result was remarkable in dominant mode of inheritance especially.

• Journal of Preventive Medicine and Public Health
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• v.53 no.6
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• pp.387-396
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• 2020

Objectives: The lack of advance planning in a public health emergency can lead to wasted resources and inadvertent loss of lives. This study is aimed at forecasting the needs for healthcare resources following the expansion of the coronavirus disease 2019 (COVID-19) outbreak in the Republic of Kazakhstan, focusing on hospital beds, equipment, and the professional workforce in light of the developing epidemiological situation and the data on resources currently available. Methods: We constructed a forecast model of the epidemiological scenario via the classic susceptible-exposed-infected-removed (SEIR) approach. The World Health Organization's COVID-19 Essential Supplies Forecasting Tool was used to evaluate the healthcare resources needed for the next 12 weeks. Results: Over the forecast period, there will be 104 713.7 hospital admissions due to severe disease and 34 904.5 hospital admissions due to critical disease. This will require 47 247.7 beds for severe disease and 1929.9 beds for critical disease at the peak of the COVID-19 outbreak. There will also be high needs for all categories of healthcare workers and for both diagnostic and treatment equipment. Thus, Republic of Kazakhstan faces the need for a rapid increase in available healthcare resources and/or for finding ways to redistribute resources effectively. Conclusions: Republic of Kazakhstan will be able to reduce the rates of infections and deaths among its population by developing and following a consistent strategy targeting COVID-19 in a number of inter-related directions.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.5
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• pp.2465-2473
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• 2016

Background: This study aimed to investigate the standardized incidence and mortality rate of colorectal cancer and its relationship with the human development index (HDI) across the world in 2012. Materials and Methods: This ecologic study was conducted for assessment of the correlation between age-specific incidence rate (ASIR) and age-specific mortality rate (ASMR) with HDI and its components. Data for SIR and SMR for every country for the year 2012 were obtained from the global cancer project. We used a bivariate method for assessment of the correlation between SIR and SMR and HDI. Statistical significance was assumed at P<0.05. Statistical analyses were performed using SPSS (Version 22.0, SPSS Inc.). Results: Countries with the highest SIR of colorectal cancer in the world in 2012, were Republic of Korea, Slovakia, Hungary and countries with the highest SMR were Hungary, Croatia and Slovakia. The correlation between SIR of colorectal cancer and the HDI was 0.712 ($P{\leq}0.001$), with life expectancy at birth 0.513 ($P{\leq}0.001$), with mean years of schooling 0.641 ($P{\leq}0.001$) and with level of income per each person of the population 0.514 (P=0.013). In addition, the correlation between SMR of colorectal cancer and the HDI was 0.628 ($P{\leq}0.001$), with life expectancy at birth 0.469 ($P{\leq}0.001$), with mean years of schooling 0.592 ($P{\leq}0.001$) and with level of income per each person of the population 0.378 (P=0.013). Conclusions: The highest SIR and SMR of colorectal cancer was in the WHO Europe region. There was a positive correlation between HDI and SIR and SMR of colorectal cancer.