• Title, Summary, Keyword: Diagnostic test

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Application of Receiver Operating Characteristic (ROC) Curve for Evaluation of Diagnostic Test Performance (진단검사의 특성 평가를 위한 Receiver Operating Characteristic (ROC) 곡선의 활용)

  • Pak, Son-Il;Oh, Tae-Ho
    • Journal of Veterinary Clinics
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    • v.33 no.2
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    • pp.97-101
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    • 2016
  • In the field of clinical medicine, diagnostic accuracy studies refer to the degree of agreement between the index test and the reference standard for the discriminatory ability to identify a target disorder of interest in a patient. The receiver operating characteristic (ROC) curve offers a graphical display the trade-off between sensitivity and specificity at each cutoff for a diagnostic test and is useful in assigning the best cutoff for clinical use. In this end, the ROC curve analysis is a useful tool for estimating and comparing the accuracy of competing diagnostic tests. This paper reviews briefly the measures of diagnostic accuracy such as sensitivity, specificity, and area under the ROC curve (AUC) that is a summary measure for diagnostic accuracy across the spectrum of test results. In addition, the methods of creating an ROC curve in single diagnostic test with five-category discrete scale for disease classification from healthy individuals, meaningful interpretation of the AUC, and the applications of ROC methodology in clinical medicine to determine the optimal cutoff values have been discussed using a hypothetical example as an illustration.

Analysis of Insulation Condition in Traction Motor Stator Windings (견인전동기 고정자 권선의 절연상태 분석)

  • Kim, Hee-Dong;Park, Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.7
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    • pp.631-635
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    • 2007
  • Diagnostic, surge and ac breakdown tests are widely used to evaluate the insulation condition of stator winding in traction motor. Diagnostic test included ac current, tan delta and maximum partial discharge. The result of diagnostic test indicates that five kinds of stator windings are good condition. Surge test was peformed to confirm the healthy of turn insulation in stator windings. This test is very easy to detect the turn insulation failure between normal and defect stator windings. After completing the diagnostic test, ac breakdown test has conducted gradually increasing ac voltage, until the stator winding punctured. No. 5 stator windings failed near rated voltage of 18.9 kV The breakdown voltage of No. 1 stator windings was 13.0 kV The ac breakdown voltage of normal winding is about 1.45 times higher than that of defect windings. The failure was located in a line-end coil at the exit from the core slot.

The Use of Confidence Interval of Measures of Diagnostic Accuracy (진단검사 정확도 평가지표의 신뢰구간)

  • Oh, Tae-Ho;Pak, Son-Il
    • Journal of Veterinary Clinics
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    • v.32 no.4
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    • pp.319-323
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    • 2015
  • The performance of diagnostic test accuracy is usually summarized by a variety of statistics such as sensitivity, specificity, predictive value, likelihood ratio, and kappa. These indices are most commonly presented when evaluations of competing diagnostic tests are reported, and it is of utmost importance to compare the accuracies of diagnostic tests to decide on the best available test for certain medical disorder. However, it is important to emphasize that specific point values of these indices are merely estimates. If parameter estimates are reported without a measure of uncertainty (precision), knowledgeable readers cannot know the range within which the true values of the indices are likely to lie. Therefore, when evaluations of diagnostic accuracy are reported the precision of estimates should be stated in parallel. To reflect the precision of any estimate of a diagnostic performance characteristic or of the difference between performance characteristics, the computation of confidential interval (CI), an indicator of precision, is widely used in medical literatures in that CIs are more informative to interpret test results than the simple point estimates. The majority of peer-reviewed journals usually require CIs to be specified for descriptive estimates, whereas domestic veterinary journals seem less vigilant on this issues. This paper describes how to calculate the indices and associated CIs using practical examples when assessing diagnostic test performance.

Estimation of Insulation Diagnosis and Dielectric Strength in 6.6 kV Motor Stator Windings (6.6 kV 전동기 고정자 권선의 절연진단과 절연내력 평가)

  • Kim, Hee-Dong;Kong, Tae-Sik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.6
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    • pp.780-785
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    • 2014
  • To assess the deterioration condition of stator insulation, diagnostic and AC dielectric strength tests were performed on five high voltage (HV) motors (2,000 HP, 6.6 kV) for boiler feed-water pump (BFP). Two HV motors for BFP were installed per unit. Following the long term rewinding program, the diagnostic test was performed on five 6.6 kV motors during the planning maintenance period. After completing diagnostic test, AC dielectric strength test was done on the stator windings of HV motors. The AC dielectric strength test was conducted at 15 kV for one minute. Dielectric strength test and diagnostics test results confirmed that the stator insulation was judged to be in serviceable condition in the five 6.6 kV motors.

Optimizing the work process through improvement of reservation system (통합예약 프로그램 개선을 통한 업무 프로세스 최적화)

  • Seo, Eunhee;Chung, Yonghwan;Gu, Bonseung;Park, Jong Bin;Park, Youngjae;Park, Kyung Jin;Kin, Soo Mi;Kwoun, Soon Ahn;Dae, Chang Min;Min, Kwan Hong
    • Quality Improvement in Health Care
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    • v.19 no.1
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    • pp.64-72
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    • 2013
  • Objective: To improve customer satisfaction through accurate information using computerized automation of the test reservation system and by performing all fasting tests on the same day with one fasting. Methods: Quality improvement activities of the test reservation system of Seoul National University Bundang Hospital improves internal and external customer satisfaction at the time of test scheduling by having the reservation system reflect test order and test time automatically and making the system to increase the same day test reservation rate. Results: Test process was smooth due to accurate test reservation and information based on test priority due to the introduction of the computerized test reservation system. Internal and external customer satisfaction improved due to the marked reduction in time required for making a reservation thanks to the improvement of work process. Conclusion: Building a computerized test reservation system was an effective measure to improve external and internal customer satisfaction.

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Use of Likelihood Ratios in Evidence-based Clinical Decision Making

  • Kim, Eu-Tteum;Pak, Son-Il
    • Journal of Veterinary Clinics
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    • v.25 no.3
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    • pp.146-151
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    • 2008
  • During the clinical decision making practitioners are often faced with performing diagnostic tests to solve the presenting problems seen in the patients. The diagnostic utility of a test has traditionally been described by technical terms such as sensitivity, specificity, and positive (PPV) and negative predictive value (NPV). Although well known, clinicians are frequently unclear about the concept and application of these terms in everyday evidence-based clinical decision making. Sensitivity and specificity, which are intrinsic properties of diagnostic tests, summarizes the characteristics of the test over a population. The PPV and NPV are greatly dependent on the population prevalence of disease, and thus they do not transferable to different patients or clinical settings. Besides, considering the fact that clinicians more often interested in knowing the extent to which a test result could confirm or exclude of a condition under consideration (posttest probability), these measures do not provide answers on this question. The likelihood ratios (LR) using the information contained in sensitivity and specificity are becoming increasingly popular for reporting the usefulness of diagnostic tests because this term provide an indication of posttest probability as a function of the pretest probability. In this article, clinical applications of LR are illustrated with some practical examples. Discussion is also included of the inherent limitations regarding diagnostic test characteristics.

Reliability of Stool Antigen Tests: Investigation of the Diagnostic Value of a New Immunochromatographic Helicobacter pylori Approach in Dyspeptic Patients

  • Korkmaz, Huseyin;Findik, Duygu;Ugurluoglu, Ceyha;Terzi, Yuksel
    • Asian Pacific Journal of Cancer Prevention
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    • v.16 no.2
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    • pp.657-660
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    • 2015
  • Background: A diagnosis of H. pylori infection can be made by invasive or non-invasive methods. Several noninvasive diagnostic tests based on the detection of H. pylori stool antigen (HpSA) have been developed. The Genx H. pylori stool antigen card test is a new rapid, non-invasive test that is based on monoclonal immunochromatographic assay. The aim of this study was to determine its sensitivity, specificity, and diagnostic accuracy for diagnosing H. pylori infection in adult patients. Materials and Methods: A total of 162 patients were included in the study. A gastric biopsy was collected for histopathology and rapid urease testing. Stool specimens for HpSA testing were also collected. Patients were considered H. pylori positive if two invasive tests (histological and rapid urease tests) were positive. Results: Using the reference test, 50.6% of the samples were positive for H. pylori infection. The Genx H. pylori antigen test was positive in 19.7% of patients. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of the Genx H. pylori antigen test were 51.6%, 96.0%, 88.8%, 76.1%, and 79.0%, respectively. Conclusions: The Genx H. pylori stool antigen card test is a new non-invasive method that is fast and simple to perform but provides less reliable results.

Quantile-based Nonparametric Test for Comparing Two Diagnostic Tests

  • Kim, Young-Min;Song, Hae-Hiang
    • Communications for Statistical Applications and Methods
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    • v.14 no.3
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    • pp.609-621
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    • 2007
  • Diagnostic test results, which are approximately normal with a few number of outliers, but non-normal probability distribution, are frequently observed in practice. In the evaluation of two diagnostic tests, Greenhouse and Mantel (1950) proposed a parametric test under the assumption of normality but this test is inappropriate for the above non-normal case. In this paper, we propose a computationally simple nonparametric test that is based on quantile estimators of mean and standard deviation, instead of the moment-based mean and standard deviation as in some parametric tests. Parametric and nonparametric tests are compared with simulations under the assumption of, respectively, normality and non-normality, and under various combinations of the probability distributions for the normal and diseased groups.

Comparative Assessment of Diagnostic Performances of Two Commercial Rapid Diagnostic Test Kits for Detection of Plasmodium spp. in Ugandan Patients with Malaria

  • Bahk, Young Yil;Park, Seo Hye;Lee, Woojoo;Jin, Kyoung;Ahn, Seong Kyu;Na, Byoung-Kuk;Kim, Tong-Soo
    • The Korean Journal of Parasitology
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    • v.56 no.5
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    • pp.447-452
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    • 2018
  • Prompt diagnosis of malaria cases with rapid diagnostic tests (RDTs) has been widely adopted as an effective malaria diagnostic tool in many malaria endemic countries, primarily due to their easy operation, fast result output, and straightforward interpretation. However, there has been controversy about the diagnostic accuracy of RDTs. This study was conducted to evaluate the diagnostic performances of the 2 commercially available malaria RDT kits, RapiGEN Malaria Ag Pf/Pv (pLDH/pLDH) and Asan $EasyTest^{TM}$ Malaria Ag Pf/Pv (HRP-2/pLDH) for their abilities to detect Plasmodium species in blood samples collected from Ugandan patients with malaria. To evaluate the diagnostic performances of these 2 RDT kits, 229 blood samples were tested for malaria infection by microscopic examination and a species-specific nested polymerase chain reaction. The detection sensitivities for P. falciparum of Malaria Ag Pf/Pv (pLDH/pLDH) and Asan $EasyTest^{TM}$ Malaria Ag Pf/Pv (HRP-2/pLDH) were 87.83% and 89.57%, respectively. The specificities of the 2 RDTs were 100% for P. falciparum and mixed P. falciparum/P. vivax infections. These results suggest that the 2 RDT kits showed reasonable levels of diagnostic performances for detection of the malaria parasites from Ugandan patients. However, neither kit could effectively detect P. falciparum infections with low parasitaemia (<$500parasites/{\mu}l$).

Development of Automated Rapid Influenza Diagnostic Test Method Based on Image Recognition (영상 인식 기반 신속 인플루엔자 자동 판독 기법 개발)

  • Lee, Ji Eun;Joo, Yoon Ha;Lee, Jung Chan
    • Journal of Biomedical Engineering Research
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    • v.40 no.3
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    • pp.97-104
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    • 2019
  • To examine different types of influenza diagnostic test kits automatically, automated rapid influenza diagnostic test method based on image recognition is proposed in this paper. First, the proposed methods classify a variety of the rapid influenza diagnostic test kit based on support vector machine that analyzes the kits' feature point. Then, to improve the accuracy of test, the proposed methods match the histogram of both the target image of influenza kit and the input image of influenza kit for minimizing the effect of environment factors, such as lighting and exposure variations. And, to minimize the effect from composition of the hand-helds devices, the proposed methods extract the feature point and match point-by-point between target image of influenza kit and input image of influenza kit. Experimental results of 124 experimental group show that the proposed methods significantly have effectiveness, which shows 90% accuracy in moderate antigen, for the preliminary examination of influenza, and provides the opportunity for taking action against influenza.