의학연구 및 의학 논문의 질을 향상시키기 위한 통계적 고려사항

안형진 ( Hyong Gin An ) 대한골절학회 2014 대한골절학회지 Vol.27 No.2

본 종설에서는 의학연구 및 의학논문의 질을 향상시키기 위한 통계적 고려사항에 관하여 간략하게 살펴보았다. 좀 더 질 높은 의학 연구를 수행하기 위해서는 연구설계 단계에서 연구의 목적을 명확하게 설정하고 이에 알맞은 연구설계를 계획하여 자료를 수집하고 적절하고 올바른 통계분석을 통하여 과학적인 결론을 도출하고 해석해야 한다. 또한 질 높은 논문을 작성하기 위해서는 이러한 일련의 과정을 명확하게 논문에 기술하여야 한다. 본 종설이 골절학 분야를 포함한 의학연구 수행 및 논문 작성에 도움이 되길 바란다.

Poster Presentation : Predicting Significant Fibrosis Using Non-Invasive Methods in Patients with Chronic Hepatitis B (초)

Yeon Seok Seo,Kwang Gyun Lee,Hyong Gin An,Jae Youn Cheong,Hyung Joon Yim,Sung Won Cho,Soon Ho Um,Chang Duck Kim,Ho Sang Ryu 대한간학회 2009 Clinical and Molecular Hepatology(대한간학회지) Vol.15 No.4(S)

Multinomial Group Testing with Small-Sized Pools and Application to California HIV Data: Bayesian and Bootstrap Approaches

( Jong Min Kim ),( Tae Young Heo ),( Hyong Gin An ) 한국조사연구학회 2006 춘계학술대회 발표논문집 Vol.2006 No.-

대응 짝 비열등성 임상시험에서 모의실험을 통한 ITT군과 PP군의 비교

신혜원 ( Hye Won Shin ),이준영 ( Jun Eyoung Lee ),안형진 ( Hyong Gin An ) 한국보건정보통계학회 (구 한국보건통계학회) 2011 보건정보통계학회지 Vol.36 No.2

Objectives: This research tries to evaluate proper analysis sets for matched-pair noninferiority clinical trials based on Sanchez and Chen`s work (2006). Methods: We evaluate intention-to-treat (ITT) with last observation carried forward (LOCF), ITT with mixed model for repeated measures (MIVIRM) and per-protocol (PP) using simulation study wit various scenarios. Results: From the simulation study, it is found that LOCF is simple and convenient to handle missing data, but it should be used with caution because it can result in biased effect estimation and lack of control on Type I error. On the other hand, ITT-MMERM has more control over Type Tenor and bias compared with ITT-LOCF and PP. Conclusions: In matched-pair noninferiority clinical trials, ITT with consideration of MMRM can be recommended for the primary analysis.

Clinical Significance of the Detection of Antinuclear Antibodies in Patients with Acute Hepatitis A

( Yeon Seok Seo ),( Kwang Gyun Lee ),( Eun Suk Jung ),( Hyong Gin An ),( Ji Hoon Kim ),( Jong Eun Yeon ),( Kwan Soo Byun ),( Hyung Joon Yim ),( Hong Sik Lee ),( Soon Ho Um ),( Chang Duck Kim ),( Ho Sa 대한소화기기능성질환·운동학회 2011 Gut and Liver Vol.5 No.3

Background/Aims: The findings of several recent studies suggest that antinuclear antibodies (ANAs) are frequently detected in patients with acute hepatitis A (AHA). However, the clinical significance of a positive ANA test remains uncertain. This study was performed to evaluate the clinical significance of ANAs in AHA patients. Methods: All patients admitted with AHA were consecutively enrolled in this study. An ANA assay was performed by indirect immunofluorescence during hospitalization. ANA positivity was defined as an ANA titer ≥1:80. The peak international normalized ratio (INR), peak alanine aminotransferase (ALT) and peak bilirubin levels were assessed over the duration of the hospitalization, and the incidence of AHA complications was evaluated. Results: A total of 422 patients were enrolled in this study (age, 31±7 years), of which 260 (61.6%) were men. ANAs were detected in 179 AHA patients (42.4%). The proportion of ANA-positive patients varied significantly with AHA status on the day of the ANA assay (4.7% during the prodromal period vs 52.1% during the icteric or recovery period, p<0.001) and sex (56.2% in women vs 33.8% in men, p<0.001). The ANAs became undetectable in all ANA-positive patients within 3 months. The incidence of complications, including mortality, fulminant hepatic failure, renal dysfunction, relapse, and cholestatic hepatitis, did not differ significantly between ANA-positive and ANA-negative patients. Conclusions: ANAs were detected frequently and transiently in patients with AHA, especially after their peak-ALT day. The presence of ANAs may not be associated with the clinical outcome of AHA, but simply with AHA status on the ANA assay day. (Gut Liver 2011;5:340-347)

Significance of Anti-HCV Signal-to-Cutoff Ratio in Predicting Hepatitis C Viremia

( Yeon Seok Seo ),( Eun Suk Jung ),( Jeong Han Kim ),( Young Kul Jung ),( Ji Hoon Kim ),( Hyong Gin An ),( Hyung Joon Yim ),( Jong Eun Yeon ),( Kwan Soo Byun ),( Chang Duck Kim ),( Ho Sang Ryu ),( Soo 대한내과학회 2009 The Korean Journal of Internal Medicine Vol.24 No.4

Background/Aims: Hepatitis C virus (HCV) RNA testing can be performed using qualitative or quantitative assays, and it is still unclear which is more useful as a primary test in patients positive for anti-HCV. The present study evaluated the usefulness of anti-HCV signal-to-cutoff ratio (S/CO ratio) for predicting HCV RNA results. Methods: Patients on whom a qualitative HCV RNA test was performed due to a positive anti-HCV enzyme immunoassay were enrolled. Patients were divided into viremia and no-viremia groups according to HCV RNA results. Receiver-operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic accuracy of anti-HCV S/CO for a diagnosis of viremia. Results: In total, 487 patients were enrolled. HCV RNA was positive in 301 subjects (61.8%). Age, serum ALT level, and anti-HCV S/CO ratio were significantly different between the viremia and no-viremia groups. By ROC curve analysis, anti-HCV S/CO ratio (area, 0.989; 95% confidence interval, 0.981 to 0.998) accurately predicted the presence of viremia, with a cutoff value of 10.9 (sensitivity, 94.4%; specificity, 97.3%). Conclusions: Anti-HCV S/CO ratio was found to be highly accurate at predicting HCV viremia. The anti-HCV S/CO ratio can be used to determine whether a quantitative or qualitative HCV RNA test should be used to confirm HCV viremia in patients with a positive anti-HCV by the following criteria: if the anti-HCV S/CO ratio is <10.9, a qualitative HCV RNA test can be used, and if the anti-HCV S/CO ratio is ≥10.9 a quantitative HCV RNA test can be performed. (Korean J Intern Med 2009;24:302-308)

Original Article : Serum cystatin C Level is a useful marker for the evaluation of renal function in patients with cirrhotic ascites and normal serum creatinine Levels

( Dong Jin Kim ),( Hyun Seok Kang ),( Hyuk Soon Choi ),( Hye Jin Cho ),( Eun Sun Kim ),( Bo Ra Keum ),( Hyong Gin An ),( Ji Hoon Kim ),( Yeon Seok Seo ),( Yong Sik Kim ),( Hyung Joon Yim ),( Yoon Tae 대한간학회 2011 Clinical and Molecular Hepatology(대한간학회지) Vol.17 No.2

Background/Aims: Several studies suggested that serum cystatin C (CysC) is more useful than serum creatinine (Cr) for the assessment of renal function in patients with liver cirrhosis. This study evaluated the clinical significance of CysC in patients with cirrhotic ascites and normal Cr level. Methods: We enrolled patients with cirrhotic ascites and a normal serum Cr level (<1.2 mg/dL). GFR was measured by 99mTc-DTPA renal scan. Serum Cr, CysC, and Cr clearance (CCr) were measured on the same day. Significant renal impairment and severe renal impairment were defined as GFR <60 mL/min and GFR <30 mL/min, respectively. Results: Eighty-nine patients with cirrhotic ascites were enrolled in the study (63 men and 26 women; age, 55±11 years). Forty-seven (52.8%) and 42 (47.2%) patients were in Child-Pugh grade B and C, respectively. Serum Cr and CysC levels and GFR were 0.8±0.2 mg/dL, 1.1±0.3 mg/L, and 73.4±25.5 mL/min, respectively. Significant and severe renal impairment were noted in 28 (31.5%) and 2 (2.2%) patients, respectively. GFR was well correlated with serum Cr, CysC, and e-GFRMDRD, while it was not correlated with e-GFRC&G. In multivariate analysis, only CysC was significantly correlated with GFR (β, 45.620; 95% CI, 23.042-68.198; P<0.001). Serum CysC level was the only independent predictor for significant renal impairment. Conclusions: Significant renal dysfunction was not rare in patients with cirrhotic ascites, even their serum Cr level is normal. Serum CysC is a useful marker for detecting significant renal dysfunction in these patients.

위암 수술 환자의 건강결과 측정을 위한 동반상병 측정도구의 유용성 연구

황세민,윤석준,안형식,안형진,김상후,경민호,이은경,Hwang, Se-Min,Yoon, Seok-Jun,Ahn, Hyeong-Sik,An, Hyong-Gin,Kim, Sang-Hoo,Kyeong, Min-Ho,Lee, Eun-Kyoung 대한예방의학회 2009 예방의학회지 Vol.42 No.1

Objectives : The purpose of the current study was to evaluate the usefulness of the following four comorbidity indices in gastric cancer patients who underwent surgery: Charlson Comorbidity Index(CCI), Cumulative Illness rating scale(CIRS), Index of Co-existent Disease(ICED), and Kaplan-Feinstein Scale(KFS). Methods : The study subjects were 614 adults who underwent surgery for gastric cancer at K hospital between 2005 and 2007. We examined the test-retest and inter-rater reliability of 4 comorbidity indices for 50 patients. Reliability was evaluated with Spearman rho coefficients for CCI and CIRS, while Kappa values were used for the ICED and KFS indices. Logistic regression was used to determine how these comorbidity indices affected unplanned readmission and death. Multiple regression was used for determining if the comorbidity indices affected length of stay and hospital costs. Results : The test-retest reliability of CCI and CIRS was substantial(Spearman rho=0.746 and 0.775, respectively), while for ICED and KFS was moderate(Kappa=0.476 and 0.504, respectively). The inter-rater reliability of the CCI, CIRS, and ICED was moderate(Spearman rho=0.580 and 0.668, and Kappa=0.433, respectively), but for KFS was fair(Kappa=0.383). According to the results from logistic regression, unplanned readmissions and deaths were not significantly different between the comorbidity index scores. But, according to the results from multiple linear regression, the CIRS group showed a significantly increased length of hospital stay(p<0.01). Additionally, CCI showed a significant association with increased hospital costs (p<0.01). Conclusions : This study suggests that the CCI index may be useful in the estimation of comorbidities associated with hospital costs, while the CIRS index may be useful where estimatation of comorbiditie associated with the length of hospital stay are concerned.

Gender-Differences in the Associations of Anthropometry with Postural Sway in Feet-together Stance

Kim, Jiwon,Kwon, Yuri,Kim, Jayoung,Chung, Hong-Young,Park, Sora,Kim, Chul-Seung,Eom, Gwang-Moon,Jun, Jae-Hoon,Park, Byung Kyu,An, Hyong Gin,Ryu, Je-Chung 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.10

In research for investigation of static balance performance, postural sway variables have often been normalized by each subject's height. However, evidence for such normalization has been insufficient. The aim of this study was to investigate the associations of anthropometry with postural sway and their possible gender differences. Forty young subjects (20 men and 20 women) performed quiet standing on a force platform in feet-together stance. Significant gender differences were observed in the correlation of outcome measures with anthropometry. In women, postural balance performance deteriorated (sway size increased and mean stable time reduced) and sway frequencies increased with height and weight. In contrast, men showed insignificant change in balance performance, but a reduction in sway frequency with height and weight. Stepwise multiple regressions revealed that height and weight were the major determinants of outcome measures, and that their effects on outcome measures differed between genders. Extreme care must be taken in normalization of postural sway variables by anthropometric data.

근치 절제술을 시행한 위암에서 절제림프절 수의 임상적 의의

김세진,장유진,김종한,박성수,박성흠,김승주,목영재,김종석,안형진,Kim, Se-Jin,Jang, You-Jin,Kim, Jong-Han,Park, Sung-Soo,Park, Seong-Heum,Kim, Seung-Ju,Mok, Young-Jae,Kim, Chong-Suk,Ahn, Hyong-Gin 대한위암학회 2009 대한위암학회지 Vol.9 No.4

목적: 위암의 근치 절제술에서 광범위 림프절 절제는 중요한 의미를 가지며 전이 림프절의 수가 종양의 침윤 정도와 함께 병기 결정의 기준이 되고 있다. 이에 저자들은 근치 절제술을 시행 받은 위암 환자에서 절제 림프절 수가 생존율에 미치는 영향을 분석하고 종양의 각 병기에 따라서 생존율 및 병기결정에 영향을 미치는 절제 림프절수의 최소 기준값을 구하고자 하였다. 대상 및 방법: 1992년부터 2002년까지 고려대학교병원에서 근치적 위절제술을 시행 받고 5년 이상 추적 관찰이 가능하였던 949명의 환자들을 대상으로 하였다. 조직검사결과에 따른 종양 침윤 정도에 따라 환자군을 분류하여 절제 림프절의 수를 조사하였다. 절제 림프절 수의 최소 기준값은 생존율에 유의한 차이를 보이는 최소값으로 정하였다. 결과: 종양의 크기, 위치, 림프절 병기, 전이 림프절의 수 및 절제 림프절의 수는 종양의 병기에 따라 유의한 차이를 보였다. Cox 비례위험모형을 통한 분석 결과 절제 림프절 수의 최소 기준값은 전체 환자에서는 14개였으며 각 병기별로 pT1군에서 15개, pT2군에서 28개, pT3군에서 37개의 값을 보였고 기준값 이상으로 절제된 경우 생존율이 유의하게 높았다. 결론: 근치적 위절제술을 받은 환자에서 기준값 이상의 림프절 절제가 생존을 향상시킬 수 있으며 이를 위해 외과의가 근치적 위절제술 시 기준값 이상의 림프절 절제술을 위해 노력해야 하며 병리의는 절제된 조직의 림프절 개수의 정확한 결과를 보고 하기 위해 더욱 노력해야 할 것이다. Purpose: The objectives of this study were to investigate the impact of the number of resected lymph nodes on the survival of gastric cancer patients who underwent curative resection, and to evaluate the cut-off values that can have an influence on survival on the tumor stage-stratified analysis. Materials and Methods: The subjects were 949 gastric cancer patients who underwent curative resection at Korea University Medical Center from 1992 to 2002. They were classified according to the depth of tumor invasion, and the influence of the number of resected lymph nodes on survival was investigated. The cut-off value for the number of resected lymph nodes was determined as the smallest value that showed a significant survival difference. Results: The tumor size, location, lymph node stage, the number of metastatic lymph nodes and the number of resected lymph nodes were significantly different according to the tumor stage. The average number of resected lymph nodes was about 39, and it showed linear correlation with the number of metastatic lymph nodes. On the Cox proportional hazard model, the cut-off values of the number of resected lymph nodes, as corrected by the number of metastatic lymph nodes, was 14 for all the patients, 15 for the pT1 patients, 28 for the pT2 patients and 37 for the pT3 patients, respectively. Conclusion: Retrieving a number of lymph nodes that is more than the cut-off value could improve the survival of gastric cancer patients. Surgeons should also make efforts to perform an exact and thorough D2 lymph node dissection. Therefore, we urge surgeons to perform D2 dissection and pathologists should examine an certain exact number of lymph nodes.