Propensity score matching for comparative studies: a tutorial with R and Rex

Recently, there has been considerable progress in developing new technologies and equipment for the medical field, including minimally invasive surgeries. Evaluating the effectiveness of these treatments requires study designs like randomized controlled trials.However, due to the nature of certain treatments, randomization is not always feasible, leading to the use of observational studies. The effect size estimated from observational studies is subject to selection bias caused by confounders. One method to reduce this bias is propensity scoring. This study aimed to introduce a propensity score matching process between two groups using a practical example with R. Additionally, Rex, an Excel add-in graphical user interface statistical program, is provided for researchers unfamiliar with R programming.Further techniques, such as matching with three or more groups, propensity score weighting and stratification, and imputation of missing values, are summarized to offer approaches for more complex studies not covered in this tutorial.

Analysis of the gut microbiome using extracellular vesicles in the urine of patients with colorectal cancer

Background/Aims@#We evaluated the gut microbiome using extracellular vesicles (EVs) in the urine of patients with colorectal cancer (CRC) to determine whether gut-microbe-derived EVs could be a potential biomarker for the diagnosis of CRC. @*Methods@#EVs were isolated from the urine of patients with CRC and healthy controls. DNA was extracted from the EVs, and the bacterial composition was analyzed using next-generation sequencing of the 16S rRNA. @*Results@#A total of 91 patients with CRC and 116 healthy controls were enrolled. We found some specific microbiomes that were more or less abundant in the CRC group than in the control group. The alpha-diversity of the gut microbiome was significantly lower in the CRC group than in the control group. A significant difference was observed in the beta-diversity between the groups. The alpha-diversity indices between patients with early- and late-stage CRC showed conflicting results; however, there was no significant difference in the beta-diversity according to the stage of CRC. There was no difference in the alpha- and beta-diversity of the gut microbiome corresponding to the location of CRC (proximal vs. distal). @*Conclusions@#A distinct gut microbiome is reflected in the urine EVs of patients with CRC compared with that in the healthy controls. Microbial signatures from EVs in urine could serve as potential biomarkers for the diagnosis of CRC.

Potential of Gut Microbe-Derived Extracellular Vesicles to Differentiate Inflammatory Bowel Disease Patients from Healthy Controls

Background/Aims@#This study aimed to evaluate the potential of the stool microbiome and gut microbe-derived extracellular vesicles (EVs) to differentiate between patients with inflammatory bowel disease (IBD) and healthy controls, and to predict relapse in patients with IBD. @*Methods@#Metagenomic profiling of the microbiome and bacterial EVs in stool samples of controls (n=110) and patients with IBD (n=110) was performed using 16S rRNA sequencing and then compared. Patients with IBD were divided into two enterotypes based on their microbiome, and the cumulative risk of relapse was evaluated. @*Results@#There was a significant difference in the composition of the stool microbiome and gut microbe-derived EVs between patients with IBD and controls. The alpha diversity of the microbiome in patients with IBD was significantly lower than that in controls, while the beta diversity also differed significantly between the two groups. These findings were more prominent in gut microbe-derived EVs than in the stool microbiome. The survival curve tended to be different for enterotypes based on the gut microbe-derived EVs; however, this difference was not statistically significant (log-rank test, p=0.166). In the multivariable analysis, elevated fecal calprotectin (>250 mg/kg) was the only significant risk factor associated with relapse (adjusted hazard ratio, 3.147; 95% confidence interval, 1.545 to 6.408; p=0.002). @*Conclusions@#Analysis of gut microbe-derived EVs is better at differentiating patients with IBD from healthy controls than stool microbiome analysis.

Joinpoint Regression About Injury Mortality and Hospitalization in Korea

Background@#Injury is a social problem that causes health and property losses, and it is important to identify the size and trend of injury for efficient prevention and management.Therefore, this study analyzed the trends in injury mortality and hospitalization rates from 2005 to 2019 in Korea. @*Methods@#Using mortality data by Statistics Korea and Korea National Hospital Discharge In-depth injury survey by the Korea Disease Control and Prevention Agency (KDCA), age standardized rates were calculated for death and hospitalization to analyze trends and annual changes with the joinpoint regression model. In addition, annual changes in the hospitalization rate of the transport accident and fall injuries by age group were analyzed, which are the major causes of injuries. @*Results@#From 2005 to 2019, the injury mortality rate has been on the decline, but the injury hospitalization rate has been on the rise. The annual rate of change varied depending on the injury mechanism, but the mortality rate tended to decrease or remain similar level, while the rate of hospitalization has steadily increased. In addition, by age group, injury mortality and hospitalization rates were high in the elderly. In particular, the hospitalization rate of the elderly was higher when comparing the hospitalization rate of the children in transport accidents and falls. Pedestrian transport accidents tended to decrease under the age of 15, but remained similar for those aged 65 and older, and bicycle accidents tended to increase in both groups. In addition, hospitalization rates were higher in the fall, with both groups showing a statistically significant increase in hospitalization rates caused by falls. @*Conclusion@#This study analyzed the trend of injury mortality and hospitalization and found that transport accidents and falls may vary depending on the means or age of the accident.Since injury is a big social problem that is a burden of disease, safety education and legal sanctions for injury prevention should be further improved in the future, especially by prioritizing vulnerable groups by age and detailed mechanisms of injury.

Well-being Index Scores and Subjective Health Status of Korean Healthcare Workers / 예방의학회지

Objectives@#The aim of this study was to evaluate the subjective level of health-related quality of life of Korean healthcare workers using various quality-of-life instruments. @*Methods@#This study included 992 participants, who were doctors and nurses. A survey was conducted between November 28 and December 4, 2019. Data from 954 participants divided into 3 groups (physicians, residents, and nurses) were analyzed. Four measurement tools (29 questions) were used in the survey to evaluate subjective health status and well-being. @*Results@#In the Mayo Well-being Index, burnout during work (88.5%) and emotional difficulties caused by work (84.0%) were frequently cited by the respondents. Regarding questions on burnout and emotional difficulties, residents and nurses had the highest scores (91.0 and 89.6%, respectively). Emotional problems, such as anxiety, depression, and irritability, accounted for a high percentage (73.1%) of the total, while 82.2% of respondents reported that their work schedules interfered with their leisure and family time. There was no significant difference among the groups in subjective health status. However, 10.1% of the residents experienced very low quality of life, which was a higher proportion than that of physicians (2.7%) and nurses (5.2%). @*Conclusions@#The level of well-being that Korean medical workers experienced in relation to work was lower than the results of the United States healthcare workers surveyed using the same tool. This study was unique in that it conducted a subjective quality-of-life survey on Korean healthcare workers.

Meaning and Status of Health-related Quality of Life Recognized by Medical Professionals: a Qualitative Study

Background@#Medical professionals must maintain their health to provide quality medical care to patients safely. However, the health-related quality of life of medical professionals is a complex issue that currently lacks a standardized evaluation approach. Therefore, the purpose of this study was to identify their perceptions of the health-related quality of life of medical professionals and explore ways to measure their quality of life as accurately. @*Methods@#This study explored the subjective health status and well-being of Korean medical professionals by conducting three focus group discussions (FGDs) with 12 physicians and 6 nurses (November to December 2019). In the FGD, we elicited participants' opinions on existing health-related quality of life measurement tools. Also, we analyzed transcribed data through content analysis. @*Results@#Participants in this study noted the ambiguity in the current definitions of health provided by the World Health Organization. They shared various problems of their health, mainly concerning fatigue and sleep disorders due to their work pattern. Also, participants shared anxiety, burden, and fear of negative consequences due to the complexity of their work. Participants voiced the necessity of a questionnaire on health-related quality of life that reflects the working lives of medical professionals. @*Conclusion@#Medical professionals in Korea were mainly criticizing about health-related quality of life problems caused by their work characteristics. The results of this study will provide valuable information for future health-related quality of life surveys targeting medical professionals in Korea, and also help to determine the method for monitoring the healthrelated quality of life for health professionals. In addition, the aspects and items identified by medical professionals as important for their health-related quality of life may be used as a basis for developing a new health-related quality of life measurement tools for medical professionals.

Disease-Specific Mortality and Prevalence Trends in Korea, 2002–2015

BACKGROUND@#Evaluation of mortality and prevalence trends is important for health planning and priority decision-making in health policy. This study was performed to examine disease-specific mortality and prevalence trends for diseases in Korea from 2002 to 2015.@*METHODS@#In this study, 206 mutually exclusive diseases and injuries were classified into 21 cause clusters, which were divided into three cause groups: 1) communicable, maternal, neonatal, and nutritional conditions; 2) non-communicable diseases (NCDs); and 3) injuries. Cause specific trends for age-standardized mortality and prevalence rates were analyzed by the joinpoint regression method.@*RESULTS@#Between 2002 and 2015, the age-standardized mortality declined to about 177 per 100,000 population, while the age-standardized prevalence rate increased to approximately 68,065 per 100,000 population. Among the 21 cause clusters, most of the disease mortality rates showed decreasing trends. However, neurological disorders, self-harm, and interpersonal violence included periods during which the mortality rates increased in 2002–2015. In addition, the trends for prevalence rates of human immunodeficiency virus infection and acquired immune deficiency syndrome, tuberculosis, transport injuries, and self-harm, and interpersonal violence differed from the overall prevalence rates. The annual percent change in prevalence rates for transport injuries increased during 2004–2007, and then decreased. The self-harm and interpersonal violence prevalence rates decreased from 2004 to 2014.@*CONCLUSION@#Between 2002 and 2015, overall decreasing trends in the mortality rate and increasing trends in the prevalence rate were observed for all causes in Korea. Especially, NCDs represented an important part of the increasing trends in Korea. For clusters of diseases with unusual trends, proper management must be considered.

Blood Pressure Curve for Children Less than 10 Years of Age: Findings from the Ewha Birth and Growth Cohort Study

BACKGROUND@#Routine blood pressure (BP) measurement is recommended to begin at 3 years of age, but there are no national BP reference values for Korean children less than 7 years of age. Therefore, we developed sex-, age-, and height-specific BP reference values for non-overweight children aged 3–9 years.@*METHODS@#We analyzed the data of 416, 340, 321, 323, and 332 subjects aged 3, 5, 7, 8, and 9 years, respectively, who participated in the Ewha Birth and Growth Cohort Study. BP percentile curves were generated using generalized additive models for location, scale, and shape. Reference values for the 50th, 90th, and 95th percentiles of BP were determined according to sex, age, and height percentiles.@*RESULTS@#In both boys and girls, a gradual increase in systolic blood pressure (SBP) with age was more pronounced than that in diastolic blood pressure (DBP). In boys, the reference values for 90th percentile of SBP/DBP at median height for children aged 3 and 9 years were 105/69 and 118/70, respectively. In girls, the reference values corresponding to the above conditions were 105/69 and 116/70, respectively. Among children aged 7–9 years of median height, the 90th percentile of SBP in the current study was lower and that of DBP was similar to the national reference values of Korea. For children aged < 7 years of median height, the reference value for SBP, but not that for DBP, was similar to that developed in the European study.@*CONCLUSION@#Although further research is needed, our findings could be used to help identify high BP in children less than 10 years of age.

Blood Pressure Curve for Children Less than 10 Years of Age: Findings from the Ewha Birth and Growth Cohort Study

BACKGROUND: Routine blood pressure (BP) measurement is recommended to begin at 3 years of age, but there are no national BP reference values for Korean children less than 7 years of age. Therefore, we developed sex-, age-, and height-specific BP reference values for non-overweight children aged 3–9 years.METHODS: We analyzed the data of 416, 340, 321, 323, and 332 subjects aged 3, 5, 7, 8, and 9 years, respectively, who participated in the Ewha Birth and Growth Cohort Study. BP percentile curves were generated using generalized additive models for location, scale, and shape. Reference values for the 50th, 90th, and 95th percentiles of BP were determined according to sex, age, and height percentiles.RESULTS: In both boys and girls, a gradual increase in systolic blood pressure (SBP) with age was more pronounced than that in diastolic blood pressure (DBP). In boys, the reference values for 90th percentile of SBP/DBP at median height for children aged 3 and 9 years were 105/69 and 118/70, respectively. In girls, the reference values corresponding to the above conditions were 105/69 and 116/70, respectively. Among children aged 7–9 years of median height, the 90th percentile of SBP in the current study was lower and that of DBP was similar to the national reference values of Korea. For children aged < 7 years of median height, the reference value for SBP, but not that for DBP, was similar to that developed in the European study.CONCLUSION: Although further research is needed, our findings could be used to help identify high BP in children less than 10 years of age.

Disease-Specific Mortality and Prevalence Trends in Korea, 2002–2015

BACKGROUND@#Evaluation of mortality and prevalence trends is important for health planning and priority decision-making in health policy. This study was performed to examine disease-specific mortality and prevalence trends for diseases in Korea from 2002 to 2015.@*METHODS@#In this study, 206 mutually exclusive diseases and injuries were classified into 21 cause clusters, which were divided into three cause groups: 1) communicable, maternal, neonatal, and nutritional conditions; 2) non-communicable diseases (NCDs); and 3) injuries. Cause specific trends for age-standardized mortality and prevalence rates were analyzed by the joinpoint regression method.@*RESULTS@#Between 2002 and 2015, the age-standardized mortality declined to about 177 per 100,000 population, while the age-standardized prevalence rate increased to approximately 68,065 per 100,000 population. Among the 21 cause clusters, most of the disease mortality rates showed decreasing trends. However, neurological disorders, self-harm, and interpersonal violence included periods during which the mortality rates increased in 2002–2015. In addition, the trends for prevalence rates of human immunodeficiency virus infection and acquired immune deficiency syndrome, tuberculosis, transport injuries, and self-harm, and interpersonal violence differed from the overall prevalence rates. The annual percent change in prevalence rates for transport injuries increased during 2004–2007, and then decreased. The self-harm and interpersonal violence prevalence rates decreased from 2004 to 2014.@*CONCLUSION@#Between 2002 and 2015, overall decreasing trends in the mortality rate and increasing trends in the prevalence rate were observed for all causes in Korea. Especially, NCDs represented an important part of the increasing trends in Korea. For clusters of diseases with unusual trends, proper management must be considered.

Blood Pressure Curve for Children Less than 10 Years of Age: Findings from the Ewha Birth and Growth Cohort Study

BACKGROUND@#Routine blood pressure (BP) measurement is recommended to begin at 3 years of age, but there are no national BP reference values for Korean children less than 7 years of age. Therefore, we developed sex-, age-, and height-specific BP reference values for non-overweight children aged 3–9 years.@*METHODS@#We analyzed the data of 416, 340, 321, 323, and 332 subjects aged 3, 5, 7, 8, and 9 years, respectively, who participated in the Ewha Birth and Growth Cohort Study. BP percentile curves were generated using generalized additive models for location, scale, and shape. Reference values for the 50th, 90th, and 95th percentiles of BP were determined according to sex, age, and height percentiles.@*RESULTS@#In both boys and girls, a gradual increase in systolic blood pressure (SBP) with age was more pronounced than that in diastolic blood pressure (DBP). In boys, the reference values for 90th percentile of SBP/DBP at median height for children aged 3 and 9 years were 105/69 and 118/70, respectively. In girls, the reference values corresponding to the above conditions were 105/69 and 116/70, respectively. Among children aged 7–9 years of median height, the 90th percentile of SBP in the current study was lower and that of DBP was similar to the national reference values of Korea. For children aged < 7 years of median height, the reference value for SBP, but not that for DBP, was similar to that developed in the European study.@*CONCLUSION@#Although further research is needed, our findings could be used to help identify high BP in children less than 10 years of age.

Disease-Specific Mortality and Prevalence Trends in Korea, 2002–2015

Projection of the Years of Life Lost, Years Lived with Disability, and ​Disability-Adjusted Life Years in Korea for 2030

BACKGROUND@#Projection of future trends in disease burden can facilitate setting of priorities for health policies and resource allocation. We report here projections of disease-specific mortality and the burdens of various diseases in Korea from 2016 to 2030.@*METHODS@#Separate age- and sex-specific projection models for 21 major cause clusters from 2016 to 2030 were developed by applying coherent functional data models based on historical trends from 2002 to 2015. The age- and sex-specific years of life lost (YLL) for each cause cluster were projected based on the projected number of deaths. Years lived with disability (YLD) projections were derived using the 2015 age- and sex-specific YLD to YLL ratio. The disability-adjusted life years (DALYs) was the sum of YLL and YLD.@*RESULTS@#The total number of deaths is projected to increase from 275,777 in 2015 to 421,700 in 2030, while the age-standardized death rate is projected to decrease from 586.9 in 2015 to 447.3 in 2030. The largest number of deaths is projected to be a result of neoplasms (75,758 deaths for males; 44,660 deaths for females), followed by cardiovascular and circulatory diseases (34,795 deaths for males; 48,553 deaths for females). The three leading causes of DALYs for both sexes are projected to be chronic respiratory diseases, musculoskeletal disorders, and other non-communicable diseases (NCDs).@*CONCLUSION@#We demonstrate that NCDs will continue to account for the majority of the disease burden in Korea in the future.

Estimating Nationwide Prevalence of Live Births with Down Syndrome and Their Medical Expenditures in Korea

BACKGROUND: This study aimed to estimate the nationwide prevalence of live births with Down syndrome (DS) and its trends and compare the observed and model-based predicted prevalence rates. Further, we compared the direct medical expenditures among DS and non-DS patients. METHODS: Using the health administrative data of Health Insurance Review and Assessment in Korea, we selected 2,301 children with DS who were born between 2007 and 2016 to estimate the prevalence of live births with DS, and 12,265 non-DS children who were born between 2010 and 2014 to compare the direct medical expenditures among patients. RESULTS: The prevalence of live births with DS was 5.03 per 10,000 births in 9 years, and 13% of children with DS were medical aid recipients during the study period. The medical expenditure of children with DS was about 10-fold higher than that of non-DS children and their out-of-pocket expenditure was about twice as high. CONCLUSION: The prevalence of live birth with DS is high in the low socioeconomic group and the healthcare costs for the children with DS are significantly higher than those for non-DS children. Therefore, health authorities should help mothers at lower socioeconomic levels to receive adequate antenatal care and consider the cost of medical care for children with DS.

Comparison of Patient-Physician Interaction Scores of Clinical Practice Examination between Checklists and Rating Scale / 가정의학회지

BACKGROUND: The clinical practice examination (CPX) was introduced in 2010, and the Seoul-Gyeonggi CPX Consortium developed the patient-physician interaction (PPI) assessment tool in 2004. Both institutions use rating scales on classified sections of PPI but differ in their scoring of key components. This study investigated the accuracy of standardized patient scores across rating scales by comparing checklist methods and verified the concurrent validity of two comparable PPI rating tools. METHODS: An educational CPX module dyspepsia case was administered to 116 fourth-year medical students at Hanyang University College of Medicine. One experienced standardized patient rated exams using two different PPI scales. She scored checklists composed of 43 items related to the two original PPI scales through video clips of the same students. From these checklists, we calculated Pearson's correlation coefficient. RESULTS: The correlations of total PPI score between the checklist and rating scale methods were 0.29 for the Korean Medical Licensing Examination (KMLE) tool and 0.30 for the consortium tool. The correlations between the KMLE and consortium tools were 0.74 for checklists and 0.83 for rating scales. In terms of section scores, the consortium tool showed only three significant correlations between the two methods out of seven sections and the KMLE tool showed only two statistically significant correlations out of five sections. CONCLUSION: The rating scale and checklist methods exhibited a weak relationship in the PPI assessment, but a high correlation between assessment tools using the same method. However, the current rating scale requires modification by reorganizing key scoring components through factor analysis.

Effects of Module Development and Role Play Course on Clinical Practice Examination Scores during a 4th Year Clerkship / 가정의학회지

BACKGROUND: After introduction of clinical skills assessment in the Korean Medical Licensing Examination, medical schools have reinforced both experiential learning with real patients and preparatory programs. This study was conducted to investigate whether a clinical practice examination (CPX) preparation program improves students' CPX score in terms of case specificity. METHODS: One hundred and thirteen senior students in a medical school participated in this study. During the fourth-year clerkship, 28 students (24.8%) from three rotation groups took a 3-day CPX preparation course consisting of module development, role play, and comprehensive physical exam skills training. Eleven rotation groups (n=85) were compared as control. Both the intervention and control group took two comprehensive CPXs before and after the clerkship was completed. RESULTS: There was no significant difference in age, sex, and school type between the two groups. On pre-test CPX, there was no significant difference in total and sectional scores between the two groups. On post-test CPX, total scores of the intervention group were higher than those of the control groups (69.5±4.3 vs. 67.5±4.4, P < 0.05). History taking scores were higher in intervention groups (70.0±6.0 vs. 66.0±6.6, P=0.01). The station scores of vaginal discharge with case similarity were higher in the intervention groups (73.0±6.3 vs. 68.9±9.3, P=0.03). CONCLUSION: A short CPX preparation course improved history taking ability, but its effect was greater only in a specific case, similar to the pre-course case. Whether this effect was due to the test experience or true improvement in competency requires further investigation.

Serum Lipid Levels in Relation to Consumption of Yogurt: The 2012 Korea National Health and Nutrition Examination Survey / 가정의학회지

BACKGROUND: The purpose of this study was to evaluate serum lipid levels in Korean adults after consumption of different types of yogurt. METHODS: Study subjects were 3,038 individuals (≥19 years of age) who participated in the 2012 Korean National Health and Nutrition Examination Survey. Yogurt intake was assessed with a food frequency questionnaire by using the 24-hour recall method. We conducted complex samples general linear analysis with adjustment for covariates. RESULTS: The serum triglyceride levels in the group consuming viscous yogurt were lower than those in the group consuming non-viscous yogurt. CONCLUSION: Consumption of viscous yogurt is associated with low serum triglyceride levels in Korean adults.

Effects of Nurses' Perception of Servant Leadership on Leader Effectiveness, Satisfaction and Additional Effort: Focused on the Mediating Effects of Leader Trust and Value Congruence

PURPOSE: This study was done to examine the effects of nurses' perception of servant leadership on leader effectiveness, satisfaction and promoting additional effort. The focus was the mediating effects of leader trust and value congruence. METHODS: Data were collected from 361 RN-BSN students and nurses participating in nationally attended in-service training programs. Data were analyzed using descriptive statistics and structural analysis with SPSS 17.0 windows program and Amos 7.0. RESULTS: Direct effects of nurses' perception of servant leadership were negative, but mediating effects of trust and value congruency were positively correlated with leader effectiveness, satisfaction and additional effort, that is servant leadership should be effective through mediating factors. CONCLUSION: The study results indicate that if the middle managers of nurses can build leader trust and value congruency between nurses through servant leadership, leader effectiveness, satisfaction and additional effort on the part of the nurses could result in a positive change in the long term.

Effects of Normal Saline for Maintenance of Arterial Lines of Surgical Patients

PURPOSE: The purpose of this study was to analyze the effectiveness of saline solution vs. heparinized-saline for maintenance of arterial lines and to detect changes in platelet and aPTT as physiological indexes. METHODS: In this nonequivalent control group, non-synchronized, double-blind study the effects of heparinized and saline solution on the maintenance of arterial lines were compared. Fifty five patients received the heparinized solution and fifty nine patients received the saline solution. All patients who had surgery in K-university hospital between September and December 2011 were eligible for participation in the study. RESULTS: There was no statistically significant difference between the saline and the heparin group in the maintenance time of the arterial lines or the number of irrigations. There was no statistically significant difference between the groups in changes in the number of platelets and aPTT for interaction between the groups and time intervals. CONCLUSION: The results indicate that saline solution can be used as an irrigation solution for the maintenance of arterial lines of adult surgical patients, rather than heparinized-saline, in view of potential risk factors in the use of heparin.

New Nurse Turnover Intention and Influencing Factors

PURPOSE: The study was done to identify turnover intention in new nurses according to characteristics of the nurses and other factors affecting turnover and to provide data to set up a strategy to reduce the turnover. METHODS: Data were collected from 1,077 new nurses who had less than 12 months employment experience and worked in one of 188 hospitals. Eight research instruments were used. Data analysis was done using SPSS WIN 15.0 program. RESULTS: Several factors influence new nurse turnover intention. The average score for turnover intention was 2.12. The scores for subscales were self efficacy, 3.76, nursing performance, 3.90, job satisfaction, 2.09, organization commitment, 1.28, stress, 1.32, burnout, 2.82 and nursing organizational culture, 3.29. Turnover intention was related to self efficacy, nursing performance, job satisfaction, organization commitment, stress, burnout, nursing organizational culture, duration of in-class training, duration of on the job training, number of hospital beds, length of employment and duration of employment in current workplace. The predicting factors for turnover intention were burnout, stress, duration of employment in the current workplace, self efficacy and nursing performance. Those factors explained 51.6% of turnover intention. CONCLUSION: New nurse turnover intention can be reduced by mitigating the factors affecting this intention.