A Review of the Statistical Analysis used in Clinical Articles Published on Journal of Korean Neurosurgical Society

Statistical analyses used in clinical articles published on the Journal of Korean Neurosurgical Society were identified and appropriateness of statistical aspects in reporting results was assessed. Forty seven clinical articles were selected in this study, which were published from February, 2005 to February, 2006 on the journal. The frequency of statistical analysis was as follows: descriptive statistics only 24 (51.1%), one type of statistical method 10 (21.3%), two or more methods 13 (27.6%). An assessment of statistical aspects was performed in 24 clinical articles reporting inferential statistics. Ten articles (41.7%) did not adequately describe or reference all statistical methods used. There were six articles (25.0%) not reporting the confidence level used as the critical criteria of the statistical significance. In thirteen articles (54.2%) it seems more appropriate to implement multivariate analyses in addition to univariate analyses. We recommend that the journal readers should concentrate on improving their knowledge of basic statistics and statistical review for manuscripts submitted should be sought from professionals in the fields of biostatistics and epidemiology.

Psychometric Properties of the Korean Version of the King's Health Questionnaire in Women with Stress Urinary Incontinence

PURPOSE: The purpose of this study is to evaluate the psychometric properties of the Korean version of the King's Health Questionnaire(KHQ) in patients with stress urinary incontinence. MATERIALS AND METHODS: Multicenter prospective study was undertaken in 106 patients with stress urinary incontince. Psychometric properties including discriminant validity, convergent validity were evaluated and the Cronbach's alpha coefficients were calculated. Test-retest analysis was performed and the sensitivity to clinical change before and after treatment was also evaluated. RESULTS: The psychometric properties and clinical validity of the KHQ Korean version were confirmed in 106 study population. The KHQ's good reliability was evidenced by Cronbach's alpha coefficients of>0.60, indicating to change in patients' perception of bladder condition in all domains. CONCLUSION: Our analyses confirm excellent psychometric properties for the Korean version of KHQ, which appears to provide a valid and reliable instrument for clinical usages in Korea.

Scoring Method for Early Prediction of Neonatal Chronic Lung Disease Using Modified Respiratory Parameters

In our previous study, we have demonstrated that peak inspiratory pressure over birth weight (PIP/kg) and mean airway pressure over birth weight (MAP/kg) were more significant risk factors for the development of neonatal chronic lung disease (CLD) than PIP and MAP. We aimed to develop a scoring method using the modified respiratory variables (SMUMRV) to predict CLD at early postnatal period. From 1997 to 1999, a retrospective review was performed for 197 infants <1,500 g for the development of the SMUMRV based on statistical analysis. From 2000 to 2001, calculated scores on day 4, 7 and 10 of life were obtained prospectively for 107 infants <1,500 g. Predictive values and the area under the receiver operator characteristic curve (AUC) were determined and compared with the result of the previous regression model. Gestational age, birth weight, 5 min Apgar score, PIP/kg at 12 hr of age, fractional inspired oxygen (FiO2), MAP/kg, modified oxygenation index and ventilatory mode were selected as parameters of SMUMRV. No significant differences of AUCs were found between the SMUMRV and the Yoder model. It is likely that our scoring method provides reliable values for predicting the development of CLD in very low birth weight infants.

Balloon Sheaths for Gastrointestinal Guidance and Access: A Preliminary Phantom Study

OBJECTIVE: We wanted to evaluate the feasibility and usefulness of a newly designed balloon sheath for gastrointestinal guidance and access by conducting a phantom study. MATERIALS AND METHODS: The newly designed balloon sheath consisted of an introducer sheath and a supporting balloon. A coil catheter was advanced over a guide wire into two gastroduodenal phantoms (one was with stricture and one was without stricture) ; group I was without a balloon sheath, group ll was with a deflated balloon sheath, and groups III and IV were with an inflated balloon and with the balloon in the fundus and body, respectively. Each test was performed for 2 minutes and it was repeated 10 times in each group by two researchers, and the positions reached by the catheter tip were recorded. RESULTS: Both researchers had better performances with both phantoms in order of group IV, III, II and I. In group IV, both researchers advanced the catheter tip through the fourth duodenal segment in both the phantoms. In group I, however, the catheter tip never reached the third duodenal segment in both the phantoms by both the researchers. The numeric values for the four study groups were significantly different for both the phantoms (p < 0.001). A significant difference was also found between group III and IV for both phantoms (p < 0.001). CONCLUSION: The balloon sheath seems to be feasible for clinical use, and it has good clinical potential for gastrointestinal guidance and access, particularly when the inflated balloon is placed in the gastric body.

Cost-Effectiveness Analysis of a Hyperlipidemia Mass Screening Program in Korea / 예방의학회지

OBJECTIVE: Until now, there have been no evidence-based guidelines produced for the mass screening of hyperlipidemia cases in Korea. This study was done to find the most efficient strategy for a hyperlipidemia-screening program among Korean adults. METHOD: Seven alternative strategies for hyperlipidemia screening were formulated and compared in terms of cost-effectiveness. Cost and effectiveness were estimated from social perspectives and using a two-stage screening process (initial testing and additional testing for positives from the first test). A computerized database (based on persons who had visited a health promotion center in one teaching hospital for a routine health check-up) was used to determine the cost and the outcome of various strategies. Official data was used in calculating direct and indirect costs. Effectiveness was measured according to the number of persons who needed clinical intervention for hyperlipidemia. A stratified analysis, considering age group and sex, was then done. Sensitivity analyses, focusing on several uncertain parameters, were also done. RESULTS: Of the seven test alternatives available, the most cost-effective strategy was a screening program, which consisted of an initial test of total cholesterol,high-density lipoprotein cholesterol and triglyceride. There was some variation in the rank of the cost-effectiveness ratios for the seven alternatives dependent on age group or gender. CONCLUSIONS: Current hyperlipidemia screening practice, for National Health Insurance beneficiaries, tests only the total cholesterol level with a cut-off value of 260mg/dl as an initial screening test. It is not the best strategy for cost-effectiveness, and should be modified. Different screening strategies taking age group and sex into account should be developed and used for the efficient mass screening of hyperlipidemia cases among Korean adults.

An Approach to Survey Data with Nonresponse: Evaluation of KEPEC Data with BMI / 예방의학회지

OBJECTIVES: A common problem with analyzing survey data involves incomplete data with either a nonresponse or missing data. The mail questionnaire survey conducted for collecting lifestyle variables on the members of the Korean Elderly Phamacoepidemiologic Cohort(KEPEC) in 1996 contains some nonresponse or missing data. The proper statistical method was applied to evaluate the missing pattern of a specific KEPEC data, which had no missing data in the independent variable and missing data in the response variable, BMI. METHODS: The number of study subjects was 8,689 elderly people. Initially, the BMI and significant variables that influenced the BMI were categorized. After fitting the log-linear model, the probabilities of the people on each category were estimated. The EM algorithm was implemented using a log-linear model to determine the missing mechanism causing the nonresponse. RESULTS: Age, smoking status, and a preference of spicy hot food were chosen as variables that influenced the BMI. As a result of fitting the nonignorable and ignorable nonresponse log-linear model considering these variables, the difference in the deviance in these two models was 0.0034(df=1). CONCLUSION: There is a lot of risk if an inference regarding the variables and large samples is made without considering the pattern of missing data. On the basis of these results, the missing data occurring in the BMI is the ignorable nonresponse. Therefore, when analyzing the BMI in KEPEC data, the inference can be made about the data without considering the missing data.

The Quality of Reconstructed 3D Images in Multidetector-Row Helical CT: Experimental Study Involving Scan Parameters

OBJECTIVE: To determine which multidetector-row helical CT scanning technique provides the best-quality reconstructed 3D images, and to assess differences in image quality according to the levels of the scanning parameters used. MATERIALS AND METHODS: Four objects with different surfaces and contours were scanned using multidetector-row helical CT at three detector-row collimations (1.25, 2.50, 5.00 mm), two pitches (3.0, 6.0), and three different degrees of overlap between the reconstructed slices (0%, 25%, 50%). Reconstructed 3D images of the resulting 72 sets of data were produced using volumetric rendering. The 72 images were graded on a scale from 1 (worst) to 5 (best) for each of four rating criteria, giving a mean score for each criterion and an overall mean score. Statistical analysis was used to assess differences in image quality according to scanning parameter levels. RESULTS: The mean score for each rating criterion, and the overall mean score, varied significantly according to the scanning parameter levels used. With regard to detector-row collimation and pitch, all levels of scanning parameters gave rise to significant differences, while in the degree of overlap of reconstructed slices, there were significant differences between overlap of 0% and of 50% in all levels of scanning parameters, and between overlap of 25% and of 50% in overall accuracy and overall mean score. Among the 18 scanning sequences, the highest score (4.94) was achieved with 1.25 mm detector-row collimation, 3.0 pitch, and 50% overlap between reconstructed slices. CONCLUSION: Comparison of the quality of reconstructed 3D images obtained using multidetector-row helical CT and various scanning techniques indicated that the 1.25 mm, 3.0, 50% scanning sequence was best. Quality improved as detector-row collimation decreased; as pitch was reduced from 6.0 to 3.0; and as overlap between reconstructed slices increased.

Cohort Study for the Effect of Chronic Noise Exposure on Blood Pressure among Male Workers / 예방의학회지

OBJECTIVE: Whether exposure to chronic noise induces an increase in blood pressure, or the development of hypertension, has not been established. A cohort study was performed to identify the effects of chronic noise exposure on blood pressure. METHODS: 530 males working at a metal manufacturing factory in Busan, Korea were enrolled for the study. They were monitored for 9 consecutive years, from 1991 to 1999, with an annual health check-up. The subjects were divided into 4 groups, which were determines by noise level categories(NLC) according to noise intensity ; NLC-I: office workers, exposed to noise a level below 60dB(A); NLC-II: field technical supporters or supervisors, frequently exposed to workplace noise, wearing no hearing protection device; NLC-III: workers, exposed to workplace noise below 85 dB(A), wearing ear plugs or muffs; NLC-IV: workers, exposed to workplace noise over 85 dB(A), wearing both ear plugs and muffs. RESULTS: After controlling possible confoundens, such as baseline age, smoking, alcohol intake, exercise, family history of hypertension, systolic(SBP) or diastolic blood pressure(DBP) and changes in BMI (body mass index), the pooled mean for the systolic blood pressures, over the duration of the study period, were 3.8mmHg, 2.0mmHg and 1.7mmHg higher in NLC-IV, NLC-III NLC-II groups, respectively, than in the NLC-I group. There were no significant differences in the diastolic blood pressures between the groups. CONCLUSION: This study suggests that chronic noise exposure increases systolic blood pressure independently, among male workers.

Inter-hospital Comparison of Cesarean Section Rates after Risk Adjustment / 예방의학회지

OBJECTIVE: To determine the clinical risk factors associated with the mode of delivery decision and to compare cesarean section rates after adjusting for risk factors identified among Korean hospitals. METHODS: Data were collected from 9 general hospitals in two provincial regions by medical record abstraction during February 2000. A total of 3,467 cases were enrolled and analyzed by stepwise logistic regression. Performance of the risk-adjustment model (discrimination and calibration) was evaluated by the C statistic and the Hosmer-Lemeshow test. Crude rates, predicted rates with 95% confidence intervals, and adjusted rates of cesarean section were calculated and compared among the hospitals. RESULTS: The average crude cesarean section rate was 53.2%, ranging from 39.4% to 65.7%. Several risk factors such as maternal age, previous history of cesarean section, placenta previa, placental abruption, malpresentation, amniotic fluid abnormality, gestational anemia, infant body weight, pregnancy-induced hypertension, and chorioamnionitis were found to have statistically significant effects on the mode of delivery. It was confirmed that information about most of these risk factors was able to be collected through the national health insurance claims database in Korea. Performance of the risk-adjustment model was good (c statistic=0.815, Hosmer-Lemeshow test=0.0621). Risk factor adjustment did lead to some change in the rank of hospital cesarean section rates. The crude rates of three hospitals were beyond 95% confidence intervals of the predicted rates. CONCLUSIONS: Considering that cesarean section rates in Korean hospitals are too high, it is apparent that some policy interventions need to be introduced. The concept and methodology of risk adjustment should be used in the process of health policy development to lower the cesarean section rate in Korea.

Factors Affecting Supply of Mental Health Care Services in Korea / 신경정신의학

OBJECTIVES: The purpose of the study is to investigate the factors affecting adequate provision of mental health care services to the psychiatric patients in mental hospitals and to suggest the introduction of a new reimbursement schedule for treatment of chronic Medicaid patients in order to avoid long-term hospitalization and to meet rising cost. METHOD: Five hundred and seventy-five psychiatric patients chosen by the stratified random sampling in six hospitals in Korea; three mental hospitals and three general hospitals, have been classified into three groups: two groups were selected from mental hospitals with the national health insurance system and Medicaid, while only one group from general hospitals with the national health insurance system. They were investigated about mental health care services provided for one week, which are transformed into financial cost by using Korean Resource Based Relative Value Scale points. The severity of their psychiatric symptoms were assessed with RAI-MH(Resident Assessment Instrument-Mental Health). RESULTS: When the Medicaid was compared to the health insurance in mental hospitals, sixty-seven percent was the relative ratio. Mental hospitals compared to general hospitals under health insurance, it was only 31%. The longer the hospitalization, the lesser services they received in all three groups. CONCLUSION: The significant factors affecting supply of mental health care services in Korean mental hospitals were duration of hospitalization, type of hospital, type of reimbursement. The introduction of Medicaid system, differentiated by duration of stay, may induce short-term hospitalization and prohibit deficient service care, especially in acute patients under Medicaid system.

The Prevalence of Hypertension in the Rural Area of Korea / 대한내과학회지

OBJECTIVES: To establish prevalence of hypertension in rural area of Korea, we surveyed adult residents older than 30 years, based on the recommendation and classification of JNC-5(Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure). METHODS: From December 1996 to February 1997, we studied 4,209 persons in 41 rural areas purposely sampled nationwide. Blood pressure was checked twice at the time of the first visit and again checked twice after one week later for the person fell under hypertension criteria at the first visit. Persons fell under hypertension criteria at the first visit without second visit for recheck were categorized as suspected hypertension. For the suspected hypertension, we predicted whether fell under criteria by logistic regression model. RESULTS: 1) The distributions of blood pressures show unimodal curve, skewed to the right. The peaks of the systolic blood pressure was between 120~129mmHg, tending to move to the right for the age of 50-and-over in male, 70-and-over in female. But peaks of the diastolic blood pressure were consistent between 80~84mmHg in both sexes. The distributions of blood pressures for male were slightly deviated to the right compared with those of the female. 2) The crude prevalence rate of hypertension, defined as systolic blood pressure > or =140mmHg or diastolic blood pressure > or =90mmHg or taking anti-hypertensive medication, was 25.94%. And the prevalence rate of suspected hypertension was 5.54%. Through the logistic regression model, the prevalence of hypertension was estimated as 29.94%. Age-sex-adjusted prevalence rate for the rural area-Myon regions- was 25.94%, if adjusted to the age-sex composition of the 1995 national census population. 3) Prevalence rate was 27.76% in male and 30.03% in female, if adjusted to the age-sex composition of the base population of this study. Prevalence rate progressively increased with age, higher in men than women before about age 60. 4) Prevalence rates among eight Provinces(Do) was different. Unadjusted rates for Kyonggi Province was 24.74%, and rates for Chonnam Province was 34.18%. But there was no significant differences of the prevalence rate between inland and seaside. 5) By logistic regression model, 65.39% of stage 1 hypertension and 75.51% of stage 2 hypertension at the first visit were estimated as to be included in hypertension criteria. 6) By the JNC-5 classification, only 22.33% of the patients taking anti-hypertensive medication was being controlled. CONCLUSION: The prevalence rate of hypertension by classification of JNC-5 at rural area was 25.94%. We could not find significant differences of prevalence rate between inland and seaside. Follow-up measurement of blood pressures will be needed to establish more valid prevalence rates of hypertension.

Complementary and Alternative Medicine Use in Korea: Prevalence, Pattern of Use, and Out-of-pocket Expenditures / 예방의학회지

OBJECTIVES: To determine the prevalence, pattern, and out-of-pocket expenditure of complementary and alternative medicine (CAM) utilization in Korean adult population. METHODS: We conducted a representative telephone survey of 2,042 persons aged 18 or older. Data about any health problem, details of their use of medical doctors(MDs) offices/hospitals/ pharmacies services and CAM during the preceding 12 months were collected with structured questionnaire. RESULTS: The utilization rate of CAM among Korean adults was 29% in one year. A total of 231 kinds of CAM was identified from this survey. Annual out-of-pocket expenditure associated with CAM use in 1998 amounted to pound $1.88 billion and was comparable to 40.8% of out-of-pocket expenditure paid for MDs offices/ hospitals/pharmacies services. Among those(N=424) who paid for both MDs offices/hospitals/pharmacies services and CAM, 35.8% paid more for CAM. CAM gave more satisfaction than western medicine to those who had experience of both types of therapy. About half of CAM users were willing to recommend CAM to others. Disclosure rate to physician among CAM users was not high(40.6%). CONCLUSION: CAM became a popular source of health care in Korea. Korean spent a substantial amount of out-of-pocket money on CAM without any public control. Because CAM use is likely to be increased rapidly through lay referral system, health policy makers and health professionals should pay more attention to CAM for making appropriate utilization of CAM.

Population-adjusted Mean Age at Incidence (PAMA) for Comparing Incidence Patterns with Age in Different Populations / 한국역학회지

Standardized incidence rates have been widely used for comparing incidence patterns between populations, adjusting for differences in demographic structure. These rates can compare overall incidence levels, but to fully understand incidence patterns, an index which links incidence with age is also needed. The authors proposed a statistical method for estimating population-adjusted mean age of incidence (PAMA), based on Poisson distribution and Fieller's theorem. The index was applied with several modifications to data relating to the incidence of breast cancer among Caucasian women living in Los Angeles.