• Journal of Digestive Cancer Research
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• 제10권2호
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• pp.99-106
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• 2022

Clinical research ultimately aimed to promptly diagnose and prevent diseases through precise biomarker development. Finding the optimal cut-off point of a regularly measured biomarker can help its interpretation and ultimately help in disease investigation and diagnosis, more specifically in determining the presence of diseases. Therefore, this study aimed to use the characteristics of outcome variables in clinical research to explain how to determine the optimal cutoff point. The outcome variables can be divided into dichotomous, ordinal, and survival types. The optimal cut-off point can be determined by finding points that maximize the Youden index, extended Youden index, and log-rank statistics. This study will enable clinical researchers to accurately determine the optimal cut-off points for regularly measured biomarkers, thereby enabling prompt disease diagnosis for effective treatment.

• 한국환경보건학회지
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• 제47권4호
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• pp.320-329
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• 2021

Background: Smoking exposure may be objectively assessed through specific biomarkers. The most common biomarker for smoking is cotinine concentration in urine, and setting an optimal cut-off point can accurately classify smoking status. Such a cut-off point for Korean adolescents has never been studied. Objectives: The aim of this study was to determine a cut-off point for urinary cotinine concentration for the discrimination of smoking in adolescents. Methods: Participants were adolescents aged 13~18 years who participated in the third cycle of the Korean National Environmental Health Survey. We used urine samples to confirm the level of cotinine concentrations. Smoking status was determined by self-reported questionnaire. We identified the optimal cotinine cut-off point for discriminating smoking status using receiver operating characteristic curve analysis. Results: Of the 904 participants, 28 (3.1%) were smokers, among whom 20 (71.4%) were male. The median urinary cotinine concentrations in smokers was 218 ㎍/L (male: 215 ㎍/L, female: 303 ㎍/L), and that in non-smokers was 1.31 ㎍/L (male: 1.46 ㎍/L, female: 1.18 ㎍/L). We found significant differences in urinary cotinine concentration according to smoking status and sex (p<0.001). Urinary cotinine concentrations performed well for identifying smoking adolescents [area under the curve: 0.954 (male: 0.963, female: 0.908)]. The cut-off that optimally distinguished smokers from non-smokers was 39.85 ㎍/L (sensitivity: 89.3%, specificity: 97.4%). Male [39.85 ㎍/L (sensitivity: 90.0%, specificity: 94.9%)] had a different optimal cut-off point than female [26.26 ㎍/L (sensitivity: 87.5%, specificity: 99.6%)]. Conclusions: This study determined a cut-off point for urinary cotinine of 39.85 ㎍/L (male: 39.85 ㎍/L, female: 26.26 ㎍/L) to distinguish smokers from non-smokers in adolescents.

• 방송공학회논문지
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• 제15권6호
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• pp.845-852
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• 2010

클라이언트로부터의 요구메시지의 통계를 바탕으로 하여 방송 서버는 데이터 아이템에 대하여 최적의 컷오프 포인트를 이용하여 핫 아이템과 콜드 아이템으로 나눈다. 핫 아이템은 주기적으로 방송되는데 이 때, 방송 주기는 아이템들의 인기도, 즉 요구확률에 따라 정해진다. 핫 아이템이 방송되지 않은 빈 슬롯에는 적절한 콜드 아이템을 골라 방송하게 되는데, 이 때 대기시간과 대기 중인 요구 메시지의 수 등을 고려하여 콜드 아이템을 정한다. 최적의 컷오프 포인트를 해석적으로 구하기 위하여 평균 응답시간을 컷오프 포인트의 함수로 나타나도록 계산하였다. 요청 도착율과 아이템의 인기도를 변화하면서 수행한 시뮬레이션을 통하여 본 논문에서 제안한 방법이 기존의 방법들보다 더욱 우수한 성능을 나타냄을 보였다.

• 응용통계연구
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• 제27권3호
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• pp.501-512
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• 2014

상당수의 사업체 조사는 절사표본설계법을 사용하고 있다. 이는 절사표본설계법에서 얻은 전수층이 많은 정보를 포함하고 있어 전체 표본크기를 최소화 할 수 있는 장점이 있기 때문이다. 그러나 최근 전수층에 포함된 사업체들의 무응답률이 높아감에 따라 전수층이 가지고 있는 장점에 한계가 나타나고 있다. 이에 Lee (2011), Shin과 Lee (2013)는 표본설계 단계에서부터 주어진 허용오차를 만족하면서 전수층 규모를 최소화하는 연구를 실시하였다. 본 연구에서는 주어진 허용오차를 만족하고 Hidiroglou (1986)가 제안한 방법으로 산출 된 표본크기를 고정한 상태에서 표본층 분산에 알려진 함수를 적합하여 전수층 크기를 최소화하는 새로운 최적 절사점을 제안하였다. 또한 Hidiroglou (1986)와 Shin과 Lee (2013)가 제안한 절단분포를 이용한 방법과 본 연구에서 제안한 방법을 모의실험과 사례연구를 통해 비교하였다.

• Parasites, Hosts and Diseases
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• 제45권3호
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• pp.239-243
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• 2007

Many allergists are currently focusing on the development of new diagnostic tools, and are attempting to improve both the sensitivity and specificity. A multiple allergen simultaneous test-chemiluminescent assay (MAST-CLA) is one of the most popular diagnostic tools used in the Republic of Korea. However, there remains controversy among allergists with regard to the cut-off point for a positive result. The present study was conducted in order to determine the validity of MAST-CLA as compared with that of the skin prick test, with particular emphasis on arthropod allergens, on the basis of percentage agreement rates and k-values, and also to suggest the optimal positive cutoff points using receiver operating characteristic (ROC) curves. The study was conducted with 97 subjects (54 men, 43 women). Optimal individual cut-off points were calculated as follows; class II for Dermatophagoides farinae, class I for Dermatophagoides pteronyssinus, and trace for a cockroach mix. These findings suggest that attempting to apply optimal individual cut-off points will be a good way of improving diagnostic tests, particularly MAST-CLA.

• 대한기계학회논문집A
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• 제24권2호
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• pp.338-346
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• 2000

Although the net-shape molding of composites is generally recommended, molded composites are frequently required cutting or grinding due to the dimensional inaccuracy for precision machine elements . During the composite machining operations such as cutting and grinding, the temperature at the cutting point may increase beyond the allowed limit due to the low thermal conductivity of composites, which might degrade the matrix of composite. Therefore, in this work, the temperature at the cutting point during cut-off grinding of carbon fiber epoxy composites was measured. The cutting force and surface roughness were also measured to investigate the cut-off grinding characteristics of the composites. The experiments were performed both under dry and wet grinding conditions with respect to cutting speed and feed rate. From the experimental investigation, the optimal conditions for the composite cut-off grinding were suggested.

• 대한영상의학회지
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• 제81권1호
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• pp.157-165
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• 2020

목적 S-Shearwave를 이용하여 유방 병변을 감별하는데 있어 최적의 cut-off 값과 종괴 내 위치를 알아보고 진단적 가치를 평가하고자 한다. 대상과 방법 연구 기간 동안 197명의 여성에서 225개의 유방 병변을 평가하였다. S-Shearwave 값은 초음파 기기에서 자동적으로 생성된 사각형의 region-of-interest로 측정하였다. 병변 내 서로 다른 네 군데에서 각각 세 번 측정하였으며 세 개의 중위 값 중 최대 값을 이용해 각각의 위치에서 최적의 cut-off 값을 계산하였다. 진단적 가치는 area under the receiving operator characteristics curve (이하 AUC)를 통해 평가하였다. 결과 총 225개의 유방 병변 중 156개(69.3%)는 양성, 69개(30.7%)는 악성이었다. 평균 SShearwave 값은 악성 병변이 양성 병변에 비해 유의미하게 높았다(108.0 ± 70.0 kPa vs. 43.4 ± 38.3 kPa, p < 0.001). 하지만 병변 내 위치에 따른 값의 유의미한 차이는 없었다. Cut-off 값을 41.9 kPa로 사용했을 때, 민감도 85.7%, 특이도 63.9%, 정확도 70.7%, 양성예측도 51.7% 및 음성예측도 90.8%였다. 초음파와 S-Shearwave 간의 AUC는 유의미한 차이를 보이지 않았다(p = 0.179). 결론 S-Shearwave는 유방 병변의 감별진단을 하는데 grayscale 초음파에 필적하는 진단적 가치를 가진다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권2호
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• pp.691-694
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• 2014

Background: Tumor length in patients with esophageal cancer (EC) has recently received great attention. However, its prognostic role for EC is controversial. The purpose of our study was to characterize the prognostic value of tumor length in EC patients and offer the optimum cut-off point of tumor length by reliable statistical methods. Materials and Methods: A retrospective analysis was conducted on 71 consecutive patients with EC who underwent surgery. ROC curve analysis was used to determine the optimal cut-off point for tumor length, measured with a handheld ruler after formalin fixation. Correlations between tumor length and other factors were surveyed, and overall survival (OS) rates were compared between the two groups. Potential prognostic factors were evaluated by univariate Kaplan-Meier survival analysis. A P value less than 0.05 was considered significant. Results: There were a total of 71 patients, with a male/female divide of 43/28 and a median age of 59. Characteristics were as follows: squamous/adenocarcinoma, 65/6; median tumor length, 4 (0.9-10); cut-off point for tumor length, 4cm. Univariate analysis prognostic factors were tumor length and modality of therapy. One, three and five year OS rates were 84, 43 and 43% for tumors with ${\leq}4cm$ length, whereas the rates were 75, 9 and 0% for tumors >4 cm. There was a significant association between tumor length and age, sex, weight loss, tumor site, histology, T and N scores, differentiation, stage, modality of therapy and longitudinal margin involvement. Conclusions: Future studies for modification of the EC staging system might consider tumor length too as it is an important prognostic factor. Further assessment with larger prospective datasets and practical methods (such as endoscopy) is needed to establish an optimal cut-off point for tumor length.

• 대한지역사회영양학회지
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• 제19권5호
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• pp.490-498
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• 2014

Objectives: This study was conducted to propose the need of re-establishing the criteria of the body weight classification in the elderly. We compared the Asia-Pacific Region Criteria (APR-C) with Entropy Model Criteria (ENT-C) using Morbidity rate of chronic diseases which correlates significantly with Body Mass Index (BMI). Methods: Subjects were 886 elderly female participating in the 2007-2009 Korea National Health and Nutrition Examination Survey (KNHANES). We compared APR-C with those of ENT-C using Receiver Operating Characteristics (ROC) curve and logistic regression analysis. Results: In the case of the morbidity of hypertension, the results were as follows: Where it was in the T-off point of APR-C, sensitivity was 67.5%, specificity was 43.1%, and Youden's index was 10.6. While in the cut-off point of ENT-C, it was 56.7%, 56.6%, and 13.3 respectively. In the case of the morbidity of diabetes, the results were as follows: In the cut-off point of APR-C, Youden's index was 14.2. While in the cut-off point of ENT-C, it was 17.2 respectively. The Area Under the ROC Curve (AUC) of the subjects who had more than 2 diseases among hypertension, diabetes, and dyslipidemia was 0.615 (95% CI: 0.578-0.652). Compared to the normal group, the odds ratio of the hypertension group which will belong to the overweight or obesity was 1.79 (95% CI: 1.30-2.47) in the APR-C, and 2.04 (95% CI: 1.49-2.80) in the ENT-C (p < 0.001). Conclusions: We conclude that the optimal cut-off point of BMI to distinguish between normal weight and overweight was $24kg/m^2$ (ENT-C) rather than $23kg/m^2$ (APR-C).

• 대한통합의학회지
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• 제9권3호
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• pp.37-45
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• 2021

Purpose : This study aimed to present normative data and cut-off points for older Korean adults completing the Montreal Cognitive Assessment - Korean (MoCA-K), which is used as a screening test for mild cognitive impairment in Korea. Methods : A total of 195 healthy adults ≥60 years were recruited. All participants completed the MoCA-K and the Korean - Mini-Mental State Examination (MMSE-K) to assess their cognitive function. Participants were divided into six groups based on their age: 60-64 years, 65~69 years, 70~74 years, 75~79 years, 80~84 years, and 85~89 years. Results : The results revealed that MoCA-K score decreased significantly with age (mean score ± standard deviation [SD]; 27.63±2.80 in subjects aged 60~64 years; 27.00±2.39 in subjects aged 65~69 years; 24.94±2.96 in subjects aged 70~74 years; 24.74±3.37 in subjects aged 75~79 years; 22.59±4.72 in subjects aged 80~84 years; and 18.83±5.38 in subjects aged 85~89 years; p<.001). Additionally, MoCA-K score also increased significantly with educational level (mean score±standard deviation [SD]; 19.95±4.78 in no formal education group; 24.95±2.22 in elementary school graduated group; 26.35±2.72 in middle school graduated group; 28.32±1.36 in high school graduated group; and 28.50±1.51 in more than college graduated group; p<.001). The optimal cut-off points were 24/25 for 60~69 years old group, 21/22 for 70~79 years old group, 17/18 for 80~84 years old group, and 13/14 for 85~89 years old group. The optimal cut-off points were 15/16 for individuals who were illiterate, 22/23 for individuals with 6 years of education, 22/24 for individuals with 9 years of education, and 26/27 for individuals with 12 or more years of education. Conclusions : This study presents normative data and cut-off points for the MoCA-K in older Korean adults. This data will facilitate more accurate detection and follow-up of the risk of mild cognitive impairment in this population, taking into consideration age and education. Future studies are required that should focus on the cut-off score on the level of education according to age.