• 응용통계연구
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• 제32권4호
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• pp.593-605
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• 2019

ROC 곡선 아래 면적과 ROC 곡면 아래 부피를 이용하여 분류모형의 판별력을 측정하는 통계량인 AUC와 VUS에 관한 많은 연구가 있다. ROC 곡선을 구성하는 FPR과 TPR 모두에 제한을 두는 양방향 부분 AUC는 부분 AUC보다 더 효과적이고 정확하게 제안되었다. ROC 곡면에서도 부분 VUS 뿐만 아니라 세 방향 부분 VUS 통계량이 개발되었다. 본 연구에서는 ROC 곡선의 FPR과 TPR 모두에 제한된 두 개의 절단함수를 이용하여 확률 개념과 적분 표현으로 대안적인 AUC를 제안한다. 또한 이 AUC는 양방향 부분 AUC와 관계가 있음을 알 수 있다. ROC 곡면에서의 세 방향 부분 VUS도 절단함수를 이용하는 VUS와 관련되어 있음을 발견하였다. 그리고 이러한 대안적인 AUC와 VUS는 맨-휘트니 통계량으로 표현되고 추정된다. 정규분포와 확률표본을 기반으로 이들의 모수적인 추정 방법과 비모수적인 추정 방법을 탐색한다.

• 응용통계연구
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• 제33권5호
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• pp.541-553
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• 2020

Receiver operating characteristic (ROC) 곡선은 민감도와 특이도로 표현되며, ROC 곡선을 이용하는 최적분류점도 민감도와 특이도만을 반영하지만, 본 연구에서는 질병률과 효용을 추가하여 고려하는 기대효용함수를 연구한다. 특히 교차하는 ROC 곡선들의 area under the ROC curve (AUC) 값들이 유사한 경우에 특정한 부분의 부분 AUC를 비교해야 한다. 본 연구에서는 정의된 민감도 직선과 특이도 직선을 바탕으로 각각 높은 민감도와 특이도를 나타내는 부분 AUC를 제안한다. ROC 곡선들이 교차하고 동일한 AUC 값을 갖는 다양한 분포함수를 설정하여, 민감도 직선과 특이도 직선을 이용하여 구한 부분 AUC를 비교하면서 모형의 판별력을 향상시키는 방법을 제안한다.

• BMB Reports
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• 제46권1호
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• pp.41-46
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• 2013

Identifying genes indispensable for an organism's life and their characteristics is one of the central questions in current biological research, and hence it would be helpful to develop computational approaches towards the prediction of essential genes. The performance of a predictor is usually measured by the area under the receiver operating characteristic curve (AUC). We propose a novel method by implementing genetic algorithms to maximize the partial AUC that is restricted to a specific interval of lower false positive rate (FPR), the region relevant to follow-up experimental validation. Our predictor uses various features based on sequence information, protein-protein interaction network topology, and gene expression profiles. A feature selection wrapper was developed to alleviate the over-fitting problem and to weigh each feature's relevance to prediction. We evaluated our method using the proteome of budding yeast. Our implementation of genetic algorithms maximizing the partial AUC below 0.05 or 0.10 of FPR outperformed other popular classification methods.

• 응용통계연구
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• 제32권2호
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• pp.187-198
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• 2019

ROC와 CAP 곡선을 이용하여 다양한 정확도 측도를 바탕으로 최적분류점을 추정하는 많은 연구가 있다. 본 연구에서는 ROC와 CAP 곡선의 특정한 부분 면적을 나타내는 대안적인 통계량을 제안한다. 새롭게 정의된 부분 면적을 나타내는 통계량의 미분방정식을 이용하여 ROC와 CAP 함수와의 관계를 살펴보고, 다음으로는 ROC와 CAP 곡선에 대한 다양한 정확도 측도들의 조건에서의 최적분류점과의 관계를 유도한다. 혼합분포를 구성하는 두 종류의 분포함수를 다양한 정규분포로 가정하여 최적분류점을 설정하고, 다양한 정확도 측도들의 조건에서의 최적분류점에 대응하는 제1종과 제2종 오류의 크기를 탐색하고 토론한다.

• Journal of Pharmaceutical Investigation
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• 제37권5호
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• pp.297-303
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• 2007

The purposes of this study were to clarify the involvement of P-glycoprotein (P-gp) in the efflux of levosulpiride in knockout mice that lack the mdr1a1b gene and to evaluate the relationship between the genetic polymorphisms in MDR1 gene (exon 21) and levosulpiride disposition in healthy Korean subjects. After oral administration ($10\;{\mu}g/g$) of levosulpiride to mdr1a/1b(-/-) and wild-type mice, plasma and brain samples were obtained at 45 min. We also investigated the genotype for MDR1 (exon 21) gene in humans using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. A single oral dose of 25 mg levosulpiride was administered to 58 healthy subjects, who were based on the MDR1 genotype for the G2677T SNP. Blood samples were taken up to 36 hr after dosing. The concentrations of levosulpiride in mouse plasma and brain were statistically significant difference between the two animal groups (P<0.05). In addition, the average brain-to-plasma concentration ratio (Kp) of levosulpiride was 3.4-fold (P<0.01) higher in the mdr1a/1b(-/-) mice compared with the wild-type mice. We also found that the values of $AUC_{0-{\infty}$, partial AUC ($AUC_{0-4h}$) and $C_{max}$ were significantly different between homozygous 2677TT subjects and the subjects with at least one wild-type allele (GG and GT subjects, P=0.012 for $AUC_{0-{\infty}$; P=0.008 for $AUC_{0-4h}$; P=0.038 for $C_{max}$). The results confirm that levosulpiride is a P-gp substrate in vivo, and clearly demonstrate the effect of SNP 2677G>T in exon 21 of the MDR1 gene on levosulpiride disposition.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제5권3호
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• pp.263-267
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• 2005

Building classifiers for financial real-world classification problems is often plagued by severely overlapping and highly skewed class distribution. New performance measures such as receiver operating characteristic (ROC) curve and area under ROC curve (AUC) have been recently introduced in evaluating and building classifiers for those kind of problems. They are, however, in-effective to evaluation of classifier's discrimination performance in a particular class of the classification problems that interests lie in only a local operating range of the classifier, In this paper, a new method is proposed that enables us to directly improve classifier's discrimination performance at a desired local operating range by defining and optimizing a partial area under ROC curve or domain-specific curve, which is difficult to achieve with conventional classification accuracy based learning methods. The effectiveness of the proposed approach is demonstrated in terms of fraud detection capability in a real-world fraud detection problem compared with the MSE-based approach.

• 약학회지
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• 제52권4호
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• pp.299-305
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• 2008

Gabapentin, 1-(aminomethyl) cyclohexaneacetic acid, is a amino acid derivative, and is clinically effective in the treatment of neuropathic pain and partial seizures of epilepsy as a complementary therapy. The purpose of the present study was to evaluate the bioequivalence of two gabapentin tablets, $Neurontin^{R}$ tablet 800 mg (Pfizer Pharmaceuticals Co., Ltd.) and Gabapenin tablet 800 mg (Hanmi Pharm. Co., Ltd.), according to the guidelines of the Korea Food and Drug Administration (KFDA). The release of gabapentin from the two gabapentin formulations in vitro was tested using KP VIII Apparatus II method with 0.06 M HCI dissolution media. Twenty six healthy male subjects, $23.85{\pm}2.24$ years in age and $69.40{\pm}11.11$ kg in body weight, were divided into two groups and a randomized $2{\times}2$ crossover study was employed. After a single tablet containing 800 mg as gabapentin was orally administered, blood samples were taken at predetermined time intervals and the concentrations of gabapentin in serum were determined using HPLC with fluorescence detector. The dissolution profiles of two formulations were similar in the tested dissolution media. The pharmacokinetic parameters such as $AUC_{t}$, $C_{max}$ and $T_{max}$ were calculated, and ANOVA test was utilized for the statistical analysis of the parameters using logarithmically transformed $AUC_{t}$, $C_{max}$ and untransformed $T_{max}$. The results showed that the differences between two formulations based on the reference drug, $Neurontin^{R}$, were 1.28%, 0.63% and 0.62% for $AUC_{t}$, $C_{max}$ and $T_{max}$, respectively. There were no sequence effects between two formulations in these parameters. The 90% confidence intervals using logarithmically transformed data were within the acceptance range of log 0.8 to log 1.25 (e.g., $log0.9097{\sim}log1.1598$ and $log0.8919{\sim}log1.1262$ for $AUC_{t}$ and $C_{max}$, respectively). Thus, the criteria of the KFDA bioequivalence guideline were satisfied, indicating Gabapenin tablet 800 mg was bioequivalent to $Neurontin^{R}$ tablet 800 mg.

• 약학회지
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• 제52권3호
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• pp.195-200
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• 2008

Gabapentin, [1-(aminomethyl) cyclohexaneacetic acid], a structural analog of $\gamma$-aminobutyric acid (GABA), is being developed for the treatment of epilepsy. Unlike GABA, gabapentin crosses the blood-brain barrier after systemic administration. Gabapentin is an effective antiepileptic drug in patients with partial and secondarily generalized seizures who are uncontrolled with use of existing anticonvulsant drug therapy. The purpose of the present study was to evaluate the bioequivalence of two gabapentin 400 mg capsules, $Neurontin^{(R)}$ capsule 400 mg (Pfizer Inc.) and Gabatin capsule 400 mg (Korean Drug Co. Ltd), according to the guidelines of the Korea Food and Drug Administration (KFDA). The release of gabapentin from the two gabapentin formulations in vitro was tested using KP VIII Apparatus II method with various dissolution media (pH 1.2, 4.0, 6.8 buffer solution and water). Twenty six healthy male subjects, 23.58$\pm$1.50 years in age and 66.74$\pm$8.31 kg in body weight, were divided into two groups and a randomized 2$\times$2 cross-over study was employed. After one capsule containing 400 mg as gabapentin were orally administered, blood was taken at predetermined time intervals and the concentrations of gabapentin in serum were determined using HPLC with fluorescence detector. The dissolution profiles of two formulations were similar at all dissolution media. In addition, the pharmacokinetic parameters such as $AUC_t$, $C_{max}$ and $T_{max}$ were calculated and ANOVA test was utilized for the statistical analysis of the parameters using logarithmically transformed $AUC_t$, $C_{max}$ and untransformed $T_{max}$. The results showed that the differences between two formulations based on the reference drug, $Neurontin^{(R)}$ capsule 400 mg, were 2.04, -3.68 and 16.79% for $AUC_t$, $C_{max}$ and $T_{max}$, respectively. There were no sequence effects between two formulations in these parameters. The 90% confidence intervals using logarithmically transformed data were within the acceptance range of log 0.8 to log 1.25 (e.g., log 0.91$\sim$log 1.16 and log 0.87$\sim$log 1.11 for $AUC_t$ and $C_{max}$, respectively). Thus, the criteria of the KFDA bioequivalence guideline were satisfied, indicating Gabatin capsule 400 mg was bioequivalent to $Neurontin^{(R)}$ capsule 400 mg.

• 대한지역사회영양학회지
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• 제26권4호
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• pp.280-295
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• 2021

Objectives: This study aimed to examine the characteristics of patients according to their nutritional status as assessed by five nutritional screening tools: Patient-Generated Subjective Global Assessment (PG-SGA), NUTRISCORE, Nutritional Risk Index (NRI), Prognostic Nutritional Index (PNI), and Controlling Nutritional Status (CONUT) and to compare the agreement, sensitivity, and specificity of these tools. Methods: A total of 952 gastric cancer patients who underwent gastrectomy and chemotherapy from January 2009 to December 2012 at the Samsung Medical Center were included. We categorized patients into malnourished and normal according to the five nutritional screening tools 1 month after surgery and compared their characteristics. We also calculated the Spearman partial correlation, Cohen's Kappa coefficient, the area under the curve (AUC), sensitivity, and specificity of each pair of screening tools. Results: We observed 86.24% malnutrition based on the PG-SGA and 85.82% based on the NUTRISCORE among gastric cancer patients in our study. When we applied NRI or CONUT, however, the malnutrition levels were less than 30%. Patients with malnutrition as assessed by the PG-SGA, NUTRISCORE, or NRI had lower intakes of energy and protein compared to normal patients. When NRI, PNI, or CONUT were used to identify malnutrition, lower levels of albumin, hemoglobin, total lymphocyte count, total cholesterol, and longer postoperative hospital stays were observed among patients with malnutrition compared to those without malnutrition. We found relatively high agreement between PG-SGA and NUTRISCORE; sensitivity was 90.86% and AUC was 0.78. When we compared NRI and PNI, sensitivity was 99.64% and AUC was 0.97. AUC ranged from 0.50 to 0.67 for comparisons between CONUT and each of the other nutritional screening tools. Conclusions: Our study suggests that PG-SGA and NRI have a relatively high agreement with the NUTRISCORE and PNI, respectively. Further cohort studies are needed to examine whether the nutritional status assessed by PG-SGA, NUTRISCORE, NRI, PNI, and CONUT predicts the gastric cancer prognosis.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제26권4호
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• pp.193-200
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• 2023

Purpose: Crohn's disease (CD) is a chronic, idiopathic bowel disorder that can progress to partial or complete bowel obstruction. At present, there are no reliable diagnostic tests that can readily distinguish between acute inflammatory, purely fibrotic and mixed inflammatory and fibrotic. Our aim is to study the utility of contrast enhanced ultrasound (CEUS) in combination with shear wave elastography (SWE) to differentiate fibrotic from inflammatory strictures in children with obstructive CD of the terminal ileum. Methods: Twenty-five (19 male) children between 2016-2021 with CD of the terminal ileum were recruited into the study. Among these patients, 22 had CEUS kinetic measurements of tissue perfusion, including wash-in slope (dB/sec), peak intensity (dB), time to peak intensity (sec), area under the curve (AUC) (dB sec), and SWE. In total, 11 patients required surgery due to bowel obstruction. Histopathologic analysis was performed by a pathologist who was blinded to the CEUS and SWE test results. Results: Patients that underwent surgical resection had significantly higher mean area under the curve on CEUS compared to patients responsive to medical therapy (p=0.03). The AUC also correlated with the degree of hypertrophy and the percent fibrosis of the muscularis propria, as determined by histopathologic grading (p<0.01). There was no difference in the mean elastography measurements between these two patient groups. Conclusion: CEUS is a useful radiological technique that can help identify pediatric patients with medically refractory obstructive fibrotic strictures of the terminal ileum that should be considered for early surgical resection.