scholarly journals ROC curves refute an unequal-variance account of search asymmetry

2010 ◽  
Vol 7 (9) ◽  
pp. 723-723
Author(s):  
R. Murray
Keyword(s):  
Roc Curves ◽  
Search Asymmetry ◽  
Unequal Variance

scholarly journals On the Use of Min-Max Combination of Biomarkers to Maximize the Partial Area under the ROC Curve

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Hua Ma ◽  
Susan Halabi ◽  
Aiyi Liu
Keyword(s):  
Roc Curve ◽  
Area Under The Curve ◽  
Predictive Performance ◽  
Roc Curves ◽  
Covariance Matrices ◽  
Distributed Data ◽  
Multivariate Distributions ◽  
Unequal Variance ◽  
Line Shapes ◽  
Partial Area

Background. Evaluation of diagnostic assays and predictive performance of biomarkers based on the receiver operating characteristic (ROC) curve and the area under the ROC curve (AUC) are vital in diagnostic and targeted medicine. The partial area under the curve (pAUC) is an alternative metric focusing on a range of practical and clinical relevance of the diagnostic assay. In this article, we adopt and extend the min-max method to the estimation of the pAUC when multiple continuous scaled biomarkers are available and compare the performances of our proposed approach with existing approaches via simulations. Methods. We conducted extensive simulation studies to investigate the performance of different methods for the combination of biomarkers based on their abilities to produce the largest pAUC estimates. Data were generated from different multivariate distributions with equal and unequal variance-covariance matrices. Different shapes of the ROC curves, false positive fraction ranges, and sample size configurations were considered. We obtained the mean and standard deviation of the pAUC estimates through re-substitution and leave-one-pair-out cross-validation. Results. Our results demonstrate that the proposed method provides the largest pAUC estimates under the following three important practical scenarios: (1) multivariate normally distributed data for nondiseased and diseased participants have unequal variance-covariance matrices; or (2) the ROC curves generated from individual biomarker are relative close regardless of the latent normality distributional assumption; or (3) the ROC curves generated from individual biomarker have straight-line shapes. Conclusions. The proposed method is robust and investigators are encouraged to use this approach in the estimation of the pAUC for many practical scenarios.

Comparison of diagnostic accuracy of 18F-FDG PET, 123I-IMT- and 99mTc-MIBI SPECT

2006 ◽  
Vol 45 (01) ◽  
pp. 49-56 ◽  
Author(s):  
N. Özdemir-Sahin ◽  
P. Hipp ◽  
W. Mier ◽  
M. Eisenhut ◽  
J. Debus ◽  
...  
Keyword(s):  
Diagnostic Accuracy ◽  
Fdg Pet ◽  
Tumour Progression ◽  
Roc Curves ◽  
Low Grade ◽  
Who Grade ◽  
Pet Tracer ◽  
Patient Groups ◽  
99Mtc Mibi ◽  
Mibi Spect

Summary Aim was to evaluates the diagnostic accuracy of the SPECTtracers 3-123I-α-methyl-L-tyrosine (IMT) and 99mTc(I)- hexakis(2-methoxyisobutylisonitrile) (MIBI) as well as the PET-tracer 2-18F-2-deoxyglucose (FDG) for detecting tumour progression in irradiated low grade astrocytomas (LGA). Patients, methods: We examined 91 patients (56 males; 35 females; 44.7 ± 11.5 years), initially suffering from histologically proven LGAs (mean WHO grade II) and treated by stereotactic radiotherapy (59.0 ± 4.6 Gy). On average 21.9 ± 11.2 months after radiotherapy, patients presented new Gd-DTPA enhancing lesions on MRI, which did not allow a differentiation between progressive tumour (PT) and non-PT (nPT) at this point of time. PET scans (n=82) were acquired 45 min after injection of 208 ± 32 MBq FDG. SPECT scans started 10 min after injection of 269 ± 73 MBq IMT (n=68) and 15 min after injection of 706 ± 63 MBq MIBI (n=34). Lesions were classified as PT and nPT based on prospective follow-up (clinically, MRI) for 17.2 ± 9.9 months after PET/SPECT. Lesion-to-normal ratios (L/N) were calculated using contra lateraly mirrored reference regions for the SPECT examinations and reference regions in the contra lateral grey (GM) and white matter (WM) for FDG PET. Ratios were evaluated by Receiver Operating Characteristic (ROC) analysis. Results: In the patient groups nPT and PT, L/N ratios for FDG (GS) were 0.6 ± 0.3 vs. 1.2 ± 0.5 (p = 0.003), for FDG (WS) 1.2 ± 0.4 vs. 2.6 ± 0.4 (p <0.001), for IMT 1.1 ± 0.1 vs. 1.8 ± 0.4 (p <0.001) and for MIBI 1.6 ± 0.7 vs. 2.6 ± 2.2 (p = 0.554). Areas under the non-parametric ROC-curves were: 0.738 ± 0.059 for FDG (GS), 0.790 ± 0.057 for FDG (WS), 0.937 ± 0.037 for IMT and 0.564 ± 0.105 for MIBI. Conclusion: MIBI-SPECT examinations resulted in a low accuracy and especially in a poor sensitivity even at modest specificity values. A satisfying diagnostic accuracy was reached with FDG PET. Using WM as reference region for FDG PET, a slightly higher AUC as compared to GM was calculated. IMT yielded the best ROC characteristics and the highest diagnostic accuracy for differentiating between PT and nPT in irradiated LGA.

57Co-Bleomycin Scintigraphy in Staging of Carcinoma of the Cervix

1985 ◽  
Vol 24 (01) ◽  
pp. 48-51 ◽  
Author(s):  
K. Dursk ◽  
T. Pertyński
Keyword(s):  
Cervical Cancer ◽  
Roc Curves ◽  
Selection Of

Summary65 patients with cervical cancer at various stages of the disease were studied scintigraphically after 57Co-bleomycin administration, active urine being flushed out from the bladder continuously. The patients were submitted to other auxiliary tests and the interpretation of scintigraphic images could thus be verified. Scintigraphic data were classified semiquantitatively by scoring in the range from zero to 5. Results were evaluated in terms of ROC-curves. This method of analysis permitted selection of cut-off levels for binary decisions that yielded satisfactory sensitivity and acceptable specificity of the test.

Use of Receiver Operating Characteristic (ROC) Curves to Evaluate Computer Confidence Threshold and Clinical Performance in the Diagnosis of Appendicitis

1978 ◽  
Vol 17 (03) ◽  
pp. 157-161 ◽  
Author(s):  
F. T. De Dombal ◽  
Jane C. Horrocks
Keyword(s):  
Receiver Operating Characteristic ◽  
Operating Characteristic ◽  
Clinical Performance ◽  
Roc Curves ◽  
Final Diagnosis ◽  
Confidence Threshold ◽  
Computer Aided ◽  
Computer Confidence ◽  
Overall Performance ◽  
Receiver Operating

This paper uses simple receiver operating characteristic (ROC) curves (i) to study the effect of varying computer confidence of threshold levels and (ii) to evaluate clinical performance in the diagnosis of acute appendicitis. Over 1300 patients presenting to five centres with abdominal pain of short duration were studied in varying detail. Clinical and computer-aided diagnostic predictions were compared with the »final« diagnosis. From these studies it is concluded the simplistic setting of a 50/50 confidence threshold for the computer program is as »good« as any other. The proximity of a computer-aided system changed clinical behaviour patterns; a higher overall performance level was achieved and clinicians performance levels became associated with the »mildly conservative« end of the computers ROC curve. Prior forecasts of over-confidence or ultra-caution amongst clinicians using the computer-aided system have not been fulfilled.

Written Prescription for Over-the-Counter Nonopioid Pain Medications Does Not Increase the Likelihood of Use after Ambulatory Hand and Upper Extremity Surgery

2020 ◽  
Author(s):  
Daniel J. Lynch ◽  
James S. Lin ◽  
Kanu S. Goyal
Keyword(s):  
Postoperative Pain ◽  
Soft Tissue ◽  
Upper Extremity ◽  
Pain Control ◽  
Control Program ◽  
Postoperative Pain Control ◽  
Over The Counter ◽  
Unequal Variance ◽  
Pain Medications ◽  
Medication Consumption

Abstract Introduction This study looked to determine how providing written prescriptions of nonopioids affected postoperative pain medication usage and pain control. Materials and Methods Patients undergoing hand and upper-extremity surgery (n = 244) were recruited after the implementation of a postoperative pain control program encouraging nonopioids before opioids. Patients were grouped based on procedure type: bone (n = 66) or soft tissue (n = 178). Patients reported postoperative medication consumption and pain control scores. Two-tailed t-tests assuming unequal variance were performed to look for differences in postoperative pain control and medication consumption between those who were and were not given written prescriptions for nonopioids. Results For both soft tissue and bone procedure patients, a written prescription did not significantly affect patients’ postoperative pain control or medication consumption. Regardless of receiving a written prescription, patients who underwent soft tissue procedures consumed significantly more daily nonopioids than opioids. Conclusion Receiving written prescriptions for nonopioids may not have a significant effect on postoperative pain control or medication consumption. Patients undergoing soft tissue hand and upper extremity procedures may be more likely to consume more daily nonopioids than opioids postoperatively compared to bone procedure patients regardless of whether they receive a written prescription for nonopioids.

Evaluation of the clot burden score (cbs) for acute ischemic stroke (ais) in intent-to-treat patients.

2019 ◽  
Vol 1 (1) ◽  
pp. 11-15 ◽  
Author(s):  
Sarah Yaziz ◽  
Ahmad Sobri Muda ◽  
Wan Asyraf Wan Zaidi ◽  
Nik Azuan Nik Ismail
Keyword(s):  
Ischemic Stroke ◽  
Clinical Outcome ◽  
Acute Ischemic Stroke ◽  
Predictive Value ◽  
Area Under The Curve ◽  
Rank Correlation ◽  
Treatment Decision ◽  
Roc Curves ◽  
Significant Negative Correlation ◽  
Clot Burden

Background : The clot burden score (CBS) is a scoring system used in acute ischemic stroke (AIS) to predict patient outcome and guide treatment decision. However, CBS is not routinely practiced in many institutions. This study aimed to investigate the feasibility of CBS as a relevant predictor of good clinical outcome in AIS cases. Methods:  A retrospective data collection and review of AIS patients in a teaching hospital was done from June 2010 until June 2015. Patients were selected following the inclusion and exclusion criteria. These patients were followed up after 90 days of discharge. The Modified Rankin scale (mRS) was used to assess their outcome (functional status). Linear regression Spearman Rank correlation was performed between the CBS and mRS. The quality performance of the correlations was evaluated using Receiver operating characteristic (ROC) curves. Results: A total of 89 patients with AIS were analysed, 67.4% (n=60) male and 32.6% (n=29) female. Twenty-nine (29) patients (33.7%) had a CBS ?6, 6 patients (6.7%) had CBS <6, while 53 patients (59.6%) were deemed clot free. Ninety (90) days post insult, clinical assessment showed that 57 (67.6%) patients were functionally independent, 27 (30.3%) patients functionally dependent, and 5 (5.6%) patients were deceased. Data analysis reported a significant negative correlation (r= -0.611, p<0.001). ROC curves analysis showed an area under the curve of 0.81 at the cut-off point of 6.5. This showed that a CBS of more than 6 predicted a good mRS clinical outcome in AIS patients; with sensitivity of 98.2%, specificity of 53.1%, positive predictive value (PPV) of 76%, and negative predictive value (NPV) of 21%. Conclusion: CBS is a useful additional variable for the management of AIS cases, and should be incorporated into the routine radiological reporting for acute ischemic stroke (AIS) cases.

Conscious access to fear-relevant information is mediated by threshold

2011 ◽  
Vol 42 (2) ◽  
pp. 56-64 ◽  
Author(s):  
Remigiusz Szczepanowski
Keyword(s):  
Present Report ◽  
Intrinsic Property ◽  
Roc Curves ◽  
Relevant Information ◽  
Perceptual Processing ◽  
High Threshold ◽  
Operating Characteristics ◽  
Emotional Perception ◽  
Fearful Faces ◽  
The Subject

Conscious access to fear-relevant information is mediated by thresholdThe present report proposed a model of access consciousness to fear-relevant information according to which there is a threshold for emotional perception beyond that the subject makes hits with no false alarm. The model was examined by having the participants performed a confidence-ratings masking task with fearful faces. Measures of the thresholds for conscious access were taken by looking at the receiver operating characteristics (ROC) curves generated from a three-state low- and high-threshold (3-LHT) model by Krantz. Indeed, the analysis of the masking data revealed that the ROCs had threshold-like-nature (a two-limb shape) rather continuous (a curvilinear shape) challenging in this fashion the classical signal-detection view on perceptual processing. Moreover, the threshold ROC curve exhibited the specific y-intercepts relevant to conscious access performance. The study suggests that the threshold can be an intrinsic property of conscious access, mediating emotional contents between perceptual states and consciousness.

Constructing and model-fitting receiver operator characteristics using continuous data.

2018 ◽  
Author(s):  
Josephine Ann Urquhart ◽  
Akira O'Connor
Keyword(s):  
Signal Detection ◽  
Least Squares Method ◽  
Model Fitting ◽  
Simulated Data ◽  
Continuous Variable ◽  
Continuous Data ◽  
Model Parameters ◽  
Operating Characteristics ◽  
Unequal Variance ◽  
Discrete Discrimination

Receiver operating characteristics (ROCs) are plots which provide a visual summary of a classifier’s decision response accuracy at varying discrimination thresholds. Typical practice, particularly within psychological studies, involves plotting an ROC from a limited number of discrete thresholds before fitting signal detection parameters to the plot. We propose that additional insight into decision-making could be gained through increasing ROC resolution, using trial-by-trial measurements derived from a continuous variable, in place of discrete discrimination thresholds. Such continuous ROCs are not yet routinely used in behavioural research, which we attribute to issues of practicality (i.e. the difficulty of applying standard ROC model-fitting methodologies to continuous data). Consequently, the purpose of the current article is to provide a documented method of fitting signal detection parameters to continuous ROCs. This method reliably produces model fits equivalent to the unequal variance least squares method of model-fitting (Yonelinas et al., 1998), irrespective of the number of data points used in ROC construction. We present the suggested method in three main stages: I) building continuous ROCs, II) model-fitting to continuous ROCs and III) extracting model parameters from continuous ROCs. Throughout the article, procedures are demonstrated in Microsoft Excel, using an example continuous variable: reaction time, taken from a single-item recognition memory. Supplementary MATLAB code used for automating our procedures is also presented in Appendix B, with a validation of the procedure using simulated data shown in Appendix C.

scholarly journals MicroRNAs-1299, -126-3p and -30e-3p as Potential Diagnostic Biomarkers for Prediabetes

Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 949
Author(s):  
Cecil J. Weale ◽  
Don M. Matshazi ◽  
Saarah F. G. Davids ◽  
Shanel Raghubeer ◽  
Rajiv T. Erasmus ◽  
...  
Keyword(s):  
Receiver Operating Characteristic ◽  
Operating Characteristic ◽  
Characteristic Curve ◽  
Predictive Ability ◽  
Roc Curves ◽  
Tolerance Test ◽  
Cross Sectional Study ◽  
Oral Glucose ◽  
Cross Sectional ◽  
Receiver Operating

This cross-sectional study investigated the association of miR-1299, -126-3p and -30e-3p with and their diagnostic capability for dysglycaemia in 1273 (men, n = 345) South Africans, aged >20 years. Glycaemic status was assessed by oral glucose tolerance test (OGTT). Whole blood microRNA (miRNA) expressions were assessed using TaqMan-based reverse transcription quantitative-PCR (RT-qPCR). Receiver operating characteristic (ROC) curves assessed the ability of each miRNA to discriminate dysglycaemia, while multivariable logistic regression analyses linked expression with dysglycaemia. In all, 207 (16.2%) and 94 (7.4%) participants had prediabetes and type 2 diabetes mellitus (T2DM), respectively. All three miRNAs were significantly highly expressed in individuals with prediabetes compared to normotolerant patients, p < 0.001. miR-30e-3p and miR-126-3p were also significantly more expressed in T2DM versus normotolerant patients, p < 0.001. In multivariable logistic regressions, the three miRNAs were consistently and continuously associated with prediabetes, while only miR-126-3p was associated with T2DM. The ROC analysis indicated all three miRNAs had a significant overall predictive ability to diagnose prediabetes, diabetes and the combination of both (dysglycaemia), with the area under the receiver operating characteristic curve (AUC) being significantly higher for miR-126-3p in prediabetes. For prediabetes diagnosis, miR-126-3p (AUC = 0.760) outperformed HbA1c (AUC = 0.695), p = 0.042. These results suggest that miR-1299, -126-3p and -30e-3p are associated with prediabetes, and measuring miR-126-3p could potentially contribute to diabetes risk screening strategies.

scholarly journals Impulse oscillometry for detection of small airway dysfunction in subjects with chronic respiratory symptoms and preserved pulmonary function

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Liang-Yuan Li ◽  
Tian-Sheng Yan ◽  
Jing Yang ◽  
Yu-Qi Li ◽  
Lin-Xi Fu ◽  
...  
Keyword(s):  
Pulmonary Function ◽  
Respiratory Symptoms ◽  
Early Stage ◽  
Roc Curves ◽  
Diagnostic Value ◽  
Small Airway ◽  
Impulse Oscillometry ◽  
Additional Method ◽  
Cutoff Values ◽  
Higher Sensitivity

Abstract Background Subjects with chronic respiratory symptoms and preserved pulmonary function (PPF) may have small airway dysfunction (SAD). As the most common means to detect SAD, spirometry needs good cooperation and its reliability is controversial. Impulse oscillometry (IOS) may complete the deficiency of spirometry and have higher sensitivity. We aimed to explore the diagnostic value of IOS to detect SAD in symptomatic subjects with PPF. Methods The evaluation of symptoms, spirometry and IOS results in 209 subjects with chronic respiratory symptoms and PPF were assessed. ROC curves of IOS to detect SAD were analyzed. Results 209 subjects with chronic respiratory symptoms and PPF were included. Subjects who reported sputum had higher R5–R20 and Fres than those who didn’t. Subjects with dyspnea had higher R5, R5–R20 and AX than those without. CAT and mMRC scores correlated better with IOS parameters than with spirometry. R5, R5–R20, AX and Fres in subjects with SAD (n = 42) significantly increased compared to those without. Cutoff values for IOS parameters to detect SAD were 0.30 kPa/L s for R5, 0.015 kPa/L s for R5–R20, 0.30 kPa/L for AX and 11.23 Hz for Fres. Fres has the largest AUC (0.665, P = 0.001) among these parameters. Compared with spirometry, prevalence of SAD was higher when measured with IOS. R5 could detect the most SAD subjects with a prevalence of 60.77% and a sensitivity of 81% (AUC = 0.659, P = 0.002). Conclusion IOS is more sensitive to detect SAD than spirometry in subjects with chronic respiratory symptoms and PPF, and it correlates better with symptoms. IOS could be an additional method for SAD detection in the early stage of diseases.

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