Measure Of Concordance Research Articles

Measures of concordance and testing of independence in multivariate structure

Two random variables are concordant if one variable is large and then the other one tends to be large. Spearman’s rank correlation and Kendall’s tau can be used to measure the trend of both variables rising and falling simultaneously. For a multivariate case, most studies are based on average Spearman’s rank correlation or average Kendall’s tau, which compute bivariate measures of concordance for all pairs of variables and then average the results. A new measure of concordance which considers all the random variables simultaneously is proposed in this paper. The distribution and other relevant properties of this statistic are deduced. Since it is a U-statistic, this statistic follows an asymptotically normal distribution. Furthermore, a nonparametric test method for the independence of multivariate random variables is proposed.

On attainability of Kendall’s tau matrices and concordance signatures

Methods are developed for checking and completing systems of bivariate and multivariate Kendall’s tau concordance measures in applications where only partial information about dependencies between variables is available. The concept of a concordance signature of a multivariate continuous distribution is introduced; this is the vector of concordance probabilities for margins of all orders. It is shown that every attainable concordance signature is equal to the concordance signature of a unique mixture of the extremal copulas, that is the copulas with extremal correlation matrices consisting exclusively of 1’s and −1’s. A method of estimating an attainable concordance signature from data is derived and shown to correspond to using standard estimates of Kendall’s tau in the absence of ties. The set of attainable Kendall rank correlation matrices of multivariate continuous distributions is proved to be identical to the set of convex combinations of extremal correlation matrices, a set known as the cut polytope. A methodology for testing the attainability of concordance signatures using linear optimization and convex analysis is provided. The elliptical copulas are shown to yield a strict subset of the attainable concordance signatures as well as a strict subset of the attainable Kendall rank correlation matrices; the Student t copula is seen to converge, as the degrees of freedom tend to zero, to a mixture of extremal copulas sharing its concordance signature with all elliptical distributions that have the same correlation matrix. A characterization of the attainable signatures of equiconcordant copulas is given.

Smartphone applications for physical activity promotion from physical education

Smartphone applications (apps) are thought to be an adequate instructional strategy not only to improve the quality of the teaching in physical education (PE), but also to effectively promote leisure-time physical activity (PA) of adolescent students in this context. Although the use of smartphone apps has been generalized in PE, little is known about the curricular approach of smartphone apps to be implemented by teacher to teach specific curricular contents in PE lessons. Therefore, the aim of this research was threefold: a) to conduct a systematic search for smartphone apps focused on PA and sport; b) to assess the features, content and quality of every included smartphone app; and c) to analyze the relationships between every selected app and the secondary PE curriculum. Systematic searches were completed on Google Play Store from January 2021 to March 2021. Apps were included when they met: main goal focused on PA and sport; permitted use by underage; they are free; user scores of at least 4. The app selection process was carried out by several reviewers and concordance measures were estimated. Additionally, an app quality assessment was independently conducted by three reviewers. A total of 18 apps focused on PA were included. Particularly, eight apps were suitable for fitness, health and quality of life curricular content; two for sports content; four for body expression content; and four apps for outdoor PA content. The mean quality score was 4.00. Apps could be helpful for teachers to implement the secondary PE curriculum and effectively promote PA among adolescent students.

Predictors of laminitis development in a cohort of nonlaminitic ponies.

Quantifying risk factors for laminitis development requires improvement. To identify the most useful physical examination, metabolic and management factors to predict laminitis development in client-owned, nonlaminitic ponies. Prospective cohort study. Physical examination, metabolic and management data were collected from a pony cohort 6 monthly for up to 4years. Ponies were monitored for the development of laminitis. Metabolic data included basal plasma concentrations of ACTH ([ACTH]), adiponectin ([adiponectin]), triglycerides and glucose. Serum insulin concentrations ([insulin]) were measured in the unfasted basal state ([insulin]T0) and 60minutes ([insulin]T60) after administration of corn syrup (0.3ml/kg). Separate multivariable Cox proportional-hazards models were developed for physical, management/signalment and metabolic data and later combined into two final models. Low-, medium- and high-laminitis risk categories were defined based on basal or T60 [insulin]. Overall, 374 ponies (age 5-32years) and 891 pony-years were included in the main analysis. Laminitis incidence (95% confidence interval (CI)) was 4.8 (3.5-6.5) cases/100 pony-years. Laminitis development was associated with numerous univariable factors. Significant (P<.05) factors retained in the final multivariable models included [insulin]T0, [insulin]T60, [adiponectin] and divergent hoof growth. [ACTH] was not independently associated with laminitis. Based on [Insulin]T0, low- (<21.6 µIU/ml), medium- (21.6-45.2 µIU/ml) and high-risk (>45.2µIU/ml) categories encompassed 70, 20 and 10% of the population and had estimated 4-year laminitis incidences (95%CI) of 6 (2-9)%, 22 (10-33)% and 69 (48-82)% respectively. Based on [Insulin]T60 the low- (<53.4µIU/ml), medium- (53.4-153µIU/ml) and high-risk (≥153µIU/ml) categories comprised 60, 30 and 10% of the population and had estimated 4-year laminitis incidences (95%CI) of 3 (0-6)%, 20 (10-29)% and 73 (52-84)% respectively. Results may not apply to different insulin assays, geographical regions, breeds or management types. [Insulin]T0 or [insulin]T60 best quantify the risk of future laminitis development in nonlaminitic ponies.

Diversity of Bivariate Concordance Measures

We revisit the axioms of Scarsini, defining bivariate concordance measures for a pair of continuous random variables (X,Y); such measures can be understood as functions of the bivariate copula C associated with (X,Y). Two constructions, investigated in the works of Edwards, Mikusiński, Taylor, and Fuchs, are generalized, yielding, in particular, examples of higher than degree-two polynomial-type concordance measures, along with examples of non-polynomial-type concordance measures, and providing an incentive to investigate possible further characterizations of such concordance measures, as was achieved by Edwards and Taylor for the degree-one case.

Development of clinical prediction models for renal and cardiovascular outcomes and mortality in patients with type 2 diabetes and chronic kidney disease using time-varying predictors

AimsTo develop a set of prediction models for end-stage kidney disease (ESKD), cardiovascular outcomes, and mortality in patients with type 2 diabetes (T2D) and chronic kidney disease (CKD) using commonly measured clinical variables. MethodsWe studied 1432 participants with T2D and CKD enrolled in the Chronic Renal Insufficiency Cohort, followed for a median period of 7 years. We used Cox proportional-hazards models to model the six outcomes (ESKD, stroke, myocardial infarction (MI), congestive heart failure (CHF), death before ESKD, and all-cause mortality). We internally evaluated these models using concordance and calibration measures. ResultsThe newly developed six prediction models included 15 predictors: age at diabetes diagnosis, sex, blood pressure, body mass index, hemoglobin A1c, high density lipoprotein cholesterol, urine protein-to-creatinine ratio, estimated glomerular filtration rate, smoking status, and history of stroke, MI, CHF, ESKD, and amputation. The resulting models demonstrated good/strong discrimination (cross-validation C-index range: 0.70 to 0.90) and calibration. ConclusionsThis study provided an internally validated and useful tool for predicting individual adverse outcomes and mortality in patients with T2D and CKD. These models may inform optimal use of targeted health interventions.

On the exact region determined by Spearman’s footrule and Gini’s gamma

A concordance measure is often a better way to model dependence than Pearson’s correlation coefficient since it is invariant with respect to monotone increasing transformations of the random variables. In this paper, we focus on the relationships between Gini’s gamma and Spearman’s footrule. We establish the exact region determined by them. We also present copulas where the bounds of the region are attained. We introduce the concordance similarity measure and compute it for all pairs of (weak) concordance measures for which the exact regions determined by them are known.

Development of population-level colon cancer pathway concordance measures and association with survival.

Clinical cancer pathways help standardize healthcare delivery to optimize patient outcomes and health system costs. However, population‐level measurement of concordance between standardized pathways and actual care received is lacking. Two measures of pathway concordance were developed for a simplified colon cancer pathway map for Stage II‐III colon cancer patients in Ontario, Canada: a cumulative count of concordant events (CCCE) and the Levenshtein algorithm. Associations of concordance with patient survival were estimated using Cox proportional hazards models adjusted for patient characteristics and time‐dependent cancer‐related activities. Models were compared and the impact of including concordance scores was quantified using the likelihood ratio chi‐squared test. The ability of the measures to discriminate between survivors and decedents was compared using the C‐index. Normalized concordance scores were significantly associated with patient survival in models for cancer stage—a 10% increase in concordance for Stage II patients resulted in a CCCE score adjusted hazard ratio (aHR) of death of 0.93, 95% CI 0.88‐0.98 and a Levenshtein score aHR of 0.64, 95% CI 0.60‐0.67. A similar relationship was found for Stage III patients—a 10% increase in concordance resulted in a CCCE aHR of 0.85, 95% CI 0.81‐0.88 and a Levenshtein aHR of 0.78, 95% CI, 0.74‐0.81. Pathway concordance can be used as a tool for health systems to monitor deviations from established clinical pathways. The Levenshtein score better characterized differences between actual care and clinical pathways in a population, was more strongly associated with survival and demonstrated better patient discrimination.

Convex concordance measures

Based on the Scarsini axioms characterizing concordance measures between two random variables X and Y linked by a copula C, we introduce and discuss convex concordance measures. In their simplest form, they are dependent, except for a few degenerated cases, on a value of C at a single point (x,y) such that 0<y≤x≤12, and on the values at seven other points corresponding to this point, namely, (y,x), (x,1−y), (1−y,x), (1−x,y), (y,1−y), (1−x,1−y) and (1−y,1−x). Our approach covers, among others, such classical concordance measures as Spearman's rho, Gini's gamma, Blomqvist's beta, but also the concordance measures introduced by Fuchs and Schmidt. Though some of the introduced constructions are related to the results of Edwards, Mikusiǹski and Taylor, they offer a genuine motivation and provide a more transparent view.

A Logistic Regression Assessment to Measure Radiotherapy Clinical Pathway Concordance for Early Stages Breast Cancer Patients

This research aims to assess the essential variables that delineate the implementation of radiotherapy in the clinical pathway of breast cancer patients from Stages 0 to II. The evaluation focuses on a sample of 8602 patients collected by the SEER program from 2007 to 2012 in Atlanta. We developed a logistic regression model to measure the level of concordance for the occurrence of radiotherapy after lumpectomy surgery. We calculated the accuracy evaluation to estimate the model's pathway concordance measure. Our study determined that multiple factors, encompassing surgery type, age, cancer stage, and if radiotherapy was implemented as part of the first course of treatment combined with tumor grade and behavior, are essential for the decision to include radiotherapy in patients' clinical pathway after surgery.

Comparison of community and clinic-based blood pressure measurements: A cross-sectional study from Haiti.

Hypertension (HTN) is the leading modifiable cardiovascular disease (CVD) risk factor in low and middle-income countries, and accurate and accessible blood pressure (BP) measurement is essential for identifying persons at risk. Given the convenience and increased use of community BP screening programs in low-income settings, we compared community and clinic BP measurements for participants in the Haiti CVD Cohort Study to determine the concordance of these two measurements. Participants were recruited using multistage random sampling from March 2019 to August 2021. HTN was defined as systolic BP (SBP) ≥ 140mmHg, diastolic BP (DBP) ≥ 90mmHg or taking antihypertensives according to WHO guidelines. Factors associated with concordance versus discordance of community and clinic BP measurements were assessed with multivariable Poisson regressions. Among 2,123 participants, median age was 41 years and 62% were female. Pearson correlation coefficients for clinic versus community SBP and DBP were 0.78 and 0.77, respectively. Using community BP measurements, 36% of participants screened positive for HTN compared with 30% using clinic BPs. The majority of participants had concordant measurements of normotension (59%) or HTN (26%) across both settings, with 4% having isolated elevated clinic BP (≥140/90 in clinic with normal community BP) and 10% with isolated elevated community BP (≥140/90 in community with normal clinic BP). These results underscore community BP measurements as a feasible and accurate way to increase HTN screening and estimate HTN prevalence for vulnerable populations with barriers to clinic access.

Conditional copula models for correlated survival endpoints: Individual patient data meta-analysis of randomized controlled trials.

Correlations among survival endpoints are important for exploring surrogate endpoints of the true endpoint. With a valid surrogate endpoint tightly correlated with the true endpoint, the efficacy of a new drug/treatment can be measurable on it. However, the existing methods for measuring correlation between two endpoints impose an invalid assumption: correlation structure is constant across different treatment arms. In this article, we reconsider the definition of Kendall's concordance measure (tau) in the context of individual patient data meta-analyses of randomized controlled trials. According to our new definition of Kendall's tau, its value depends on the treatment arms. We then suggest extending the existing copula (and frailty) models so that their Kendall's tau can vary across treatment arms. Our newly proposed model, a joint frailty-conditional copula model, is the implementation of the new definition of Kendall's tau in meta-analyses. In order to facilitate our approach, we develop an original R function condCox.reg(.) and make it available in the R package joint.Cox (https://CRAN.R-project.org/package=joint.Cox). We apply the proposed method to a gastric cancer dataset (3288 patients in 14 randomized trials from the GASTRIC group). This data analysis concludes that Kendall's tau has different values between the surgical treatment arm and the adjuvant chemotherapy arm (p-value<0.001), whereas disease-free survival remains a valid surrogate at individual level for overall survival in these trials.

Implementation of an EHR-embedded decision support tool in community oncology practices.

274 Background: Clinical decision support (CDS) tools facilitate value based cancer care delivery and can enable measurement of guideline concordance, but can be challenging to implement. Flatiron Assist is an EHR-embedded and customizable CDS tool which facilitates selection and documentation of NCCN Guideline concordant and NCCN Preferred treatment regimens. We assessed performance metrics after the first year of use of this tool at eleven sites of care. Methods: We reviewed all non-small cell lung cancer (NSCLC) treatment orders as entered at 11 community practice sites of care in the northeast and southeast US from launch May 15, 2020, through May 23, 2021. Use of the CDS tool is not mandatory at these practices, and is deployed via prescriber choice. The tool documents and reports various quality metrics. We describe monthly prevalence of the CDS tool use, proportion of orders documented as guideline concordant, and prescriber-reported reasons for non-concordance. Results: All 954 NSCLC treatment regimen orders by the 89 prescribers who had the option to use the CDS tool were analyzed during the 1 year observation period. 658 regimens (69%) were ordered via the tool. Table describes prescriber users and non-users over time. The tool was deployed for 60% of NSCLC orders at 2 months, 69% at 6 months and 78% at 1 year post launch. Over the observed time period, 92% of treatment regimens ordered via the tool were documented as guideline concordant (94% at 2 months, 96% at 6 months and 85% at 1 year post-launch). Prescriber-reported reasons for ordering non-concordant regimens were “physician choice” (59%), “patient status” (12%), “newly published evidence” (10%), “second opinion from outside institution” (9%), “financial burden on patient/insurance doesn’t cover” (5%), “patient choice” (2%) and “other (allergy, disease progression, atypical disease)” (3%). Conclusions: At the study sites, this EHR-embedded CDS tool was rapidly adopted by most prescribers (approximately two thirds within 6 months of launch), and used for the majority of NSCLC candidate order sets during the 1 year observation period. NCCN concordance among users was empirically high overall and declined slightly over time, perhaps due to increased usage and/or greater comfort with the optional tool with ongoing use. Prescribers most commonly self-attributed the selection of non-concordant therapy to “physician choice” as opposed to factors such as financial hardship or patient choice. Further research will characterize workflow time, predictors of non-use and non-concordant orders, and evaluate whether Flatiron Assist improves clinical outcomes.[Table: see text]

Comparison of prevalence and exposure-disease associations using self-report and hospitalization data among enrollees of the world trade center health registry

BackgroundAlthough many studies have investigated agreement between survey and hospitalization data for disease prevalence, it is unknown whether exposure-chronic disease associations vary based on data collection method. We investigated agreement between self-report and administrative data for the following: 1) disease prevalence, and 2) the accuracy of self-reported hospitalization in the last 12 months, and 3) the association of seven chronic diseases (rheumatoid arthritis, hypertension, heart attack, stroke, asthma, diabetes, hyperlipidemia) with four measures of 9/11 exposure.MethodsEnrollees of the World Trade Center Health Registry who resided in New York State were included (N = 18,206). Hospitalization data for chronic diseases were obtained from the New York State Planning and Research Cooperative System (SPARCS). Prevalence for each disease and concordance measures (kappa, sensitivity, specificity, positive agreement, and negative agreement) were calculated. In addition, the associations of the seven chronic diseases with the four measures of exposure were evaluated using logistic regression.ResultsSelf-report disease prevalence ranged from moderately high (40.5% for hyperlipidemia) to low (3.8% for heart attack). Self-report prevalence was at least twice that obtained from administrative data for all seven chronic diseases. Kappa ranged from 0.35 (stroke) to 0.04 (rheumatoid arthritis). Self-reported hospitalizations within the last 12 months showed little overlap with actual hospitalization data. Agreement for exposure-disease associations was good over the twenty-eight exposure-disease pairs studied.ConclusionsAgreement was good for exposure-disease associations, modest for disease prevalence, and poor for self-reported hospitalizations. Neither self-report nor administrative data can be treated as the “gold standard.” Which source to use depends on the availability and context of data, and the disease under study.

Implementing work-related Mental health guidelines in general PRacticE (IMPRovE): a protocol for a hybrid III parallel cluster randomised controlled trial

BackgroundThe Clinical Guideline for the Diagnosis and Management of Work-related Mental Health Conditions in General Practice (the Guideline) was published in 2019. The objective of this trial is to implement the Guideline in general practice.Trial designImplementing work-related Mental health conditions in general PRacticE is a hybrid III, parallel cluster randomised controlled trial undertaken in Australia. Its primary aim is to assess the effectiveness of a complex intervention on the implementation of the Guideline in general practice. Secondary aims are to assess patient health and work outcomes, to evaluate the cost-effectiveness of the trial, and to develop a plan for sustainability.MethodsA total of 86 GP clusters will be randomly allocated either to the intervention arm, where they will receive a complex intervention comprising academic detailing, enrolment in a community of practice and resources, or to the control arm, where they will not receive the intervention. GP guideline concordance will be assessed at baseline and 9 months using virtual simulated patient scenarios. Patients who meet the eligibility criteria (>18years, employed, and receiving care from a participating GP for a suspected or confirmed work-related mental health condition) will be invited to complete surveys about their health and work participation and provide access to their health service use data. Data on health service use and work participation compensation claim data will be combined with measures of guideline concordance and patient outcomes to inform an economic evaluation. A realist evaluation will be conducted to inform the development of a plan for sustainability.ResultsWe anticipate that GPs who receive the intervention will have higher guideline concordance than GPs in the control group. We also anticipate that higher concordance will translate to better health and return-to-work outcomes for patients, as well as cost-savings to society.ConclusionsThe trial builds on a body of work defining the role of GPs in compensable injury, exploring their concerns, and developing evidence-based guidelines to address them. Implementation of these guidelines has the potential to deliver improvements in GP care, patient health, and return-to-work outcomes.Trial registrationACTRN12620001163998, November 2020

Comparison of swept-source versus spectral-domain optical coherence tomography angiography for detection of macular neovascularization

PurposeTo compare swept-source (SS) versus spectral-domain (SD) optical coherence tomography angiography (OCTA) for the detection of macular neovascularization (MNV).MethodsIn this prospective cohort study, 72 eyes of 54 patients with subretinal hyperreflective material (SHRM) and/or pigment epithelial detachment (PED) on OCT possibly corresponding to MNV in at least one eye were included. OCTA scans were acquired using two devices, the PLEX Elite 9000 SS-OCTA and the Spectralis SD-OCTA. Fluorescein angiography (FA) was used as reference. Two graders independently evaluated en face OCTA images using a preset slab as well as a manually modified slab, followed by a combination of en face and cross-sectional OCTA.ResultsSensitivity (specificity) for the automated slabs was 51.7% (93.0%) for SS-OCTA versus 58.6% (95.3%) for SD-OCTA. Manual modification of segmentation increased sensitivity to 79.3% for SS-OCTA but not for SD-OCTA (58.6%). The combination of en face OCTA with cross-sectional OCTA reached highest sensitivity values (SS-OCTA: 82.8%, SD-OCTA: 86.2%), and lowest number of cases with discrepancies between SS-OCTA and SD-OCTA (4.2%). Fleiss kappa as measure of concordance between FA, SS-OCTA, and SD-OCTA was 0.56 for the automated slabs, 0.60 for the manual slabs, and 0.73 (good agreement) for the combination of en face OCTA with cross-sectional OCTA. Concordance to FA was moderate for the automated slabs and good for manual slabs and combination with cross-sectional OCTA of both devices.ConclusionBoth devices reached comparable results regarding the detection of MNV on OCTA. Sensitivity for MNV detection and agreement between devices was best when evaluating a combination of en face and cross-sectional OCTA.

Comparison of the effectiveness of Martin\u2019s equation, Friedewald\u2019s equation, and a Novel equation in low-density lipoprotein cholesterol estimation

Low-density-lipoprotein cholesterol (LDL-C) is the main target in atherosclerotic cardiovascular disease (ASCVD). We aimed to validate and compare a new LDL-C estimation equation with other well-known equations. 177,111 samples were analysed from two contemporary population-based cohorts comprising asymptomatic Korean adults who underwent medical examinations. Performances of the Friedewald (FLDL), Martin (MLDL), and Sampson (SLDL) equations in estimating direct LDL-C by homogenous assay were assessed by measures of concordance (R2, RMSE, and mean absolute difference). Analyses were performed according to various triglyceride (TG) and/or LDL-C strata. Secondary analyses were conducted within dyslipidaemia populations of each database. MLDL was superior or at least similar to other equations regardless of TG/LDL-C, in both the general and dyslipidaemia populations (RMSE = 11.45/9.20 mg/dL; R2 = 0.88/0.91; vs FLDL: RMSE = 13.66/10.42 mg/dL; R2 = 0.82/0.89; vs SLDL: RMSE = 12.36/9.39 mg/dL; R2 = 0.85/0.91, per Gangnam Severance Hospital Check-up/Korea Initiatives on Coronary Artery Calcification data). MLDL had a slight advantage over SLDL with the lowest MADs across the full spectrum of TG levels, whether divided into severe hyper/non-hyper to moderate hypertriglyceridaemia samples or stratified by 100-mg/dL TG intervals, even up to TG values of 500–600 mg/dL. MLDL may be a readily adoptable and cost-effective alternative to direct LDL-C measurement, irrespective of dyslipidaemia status. In populations with relatively high prevalence of mild-to-moderate hypertriglyceridaemia, Martin’s equation may be optimal for LDL-C and ASCVD risk estimation.

Diagnostic Ability of Peguero-Lo Presti Electrocardiographic Left Ventricular Hypertrophy Criterion in Severe Aortic Stenosis.

Traditional electrocardiographic (ECG) criteria for left ventricular hypertrophy (LVH), introduced in the pre-echocardiographic era of diagnosis, have a relatively low sensitivity (usually not exceeding 25–40%) in detecting LVH. A novel Peguero-Lo Presti ECG-LVH criterion was recently shown to exhibit a higher sensitivity than the traditional ECG-LVH criteria in hypertension. Our aim was to test the diagnostic ability of the novel Peguero-Lo Presti ECG-LVH criterion in severe aortic stenosis. We retrospectively analyzed 12-lead ECG tracings and echocardiographic records from the index hospitalization of 50 patients with isolated severe aortic stenosis (mean age: 77 ± 10 years; 30 women and 20 men). Exclusion criteria included QRS > 120 ms, bundle branch blocks or left anterior fascicular block, a history of myocardial infarction, more than mild aortic or mitral regurgitation, and significant LV dysfunction by echocardiography. We compared the agreement of the novel Peguero-Lo Presti criterion and traditional ECG-LVH criteria with echocardiographic LVH (LV mass index > 95 g/m2 in women and >115 g/m2 in men). Echocardiographic LVH was found in 32 out of 50 study patients. The sensitivity of the Peguero-Lo Presti criterion in detecting LVH was improved (55% vs. 9–34%) at lower specificity (72% vs. 78–100%) in comparison to 8 single traditional ECG-LVH criteria. Additionally, the positive predictive value (77% vs. 72%), positive likelihood ratio (2.0 vs. 1.5), and odds ratio (3.2 vs. 2.4) were higher for the Peguero-Lo Presti criterion versus the presence of any of these 8 traditional ECG-LVH criteria. Cohen’s Kappa, a measure of concordance between ECG and echocardiography with regard to LVH, was 0.24 for the Peguero-Lo Presti criterion, −0.01–0.13 for single traditional criteria, and 0.20 for any traditional criterion. However, by the receiver operating characteristics (ROC) curve analysis, the overall ability to discriminate between patients with and without LVH was insignificantly lower for the Peguero-Lo Presti versus Cornell voltage as a continuous variable (area under the ROC curve: 0.65 (95% CI, 0.48–0.81) vs. 0.71 (0.55–0.86), p = 0.5). In conclusion, our preliminary results suggest a slightly better, albeit still low, agreement of the novel Peguero-Lo Presti ECG criterion compared to the traditional ECG-LVH criteria with echocardiographic LVH in severe aortic stenosis.

Concordance measures and time-dependent ROC methods

The receiver operating characteristic (ROC) curve displays sensitivity versus 1-specificity over a set of thresholds. The area under the ROC curve (AUC) is a global scalar summary of this curve. In the context of time-dependent ROC methods, we are interested in global scalar measures that summarize sequences of time-dependent AUCs over time. The concordance probability is a candidate for such purposes. The concordance probability can provide a global assessment of the discrimination ability of a test for an event that occurs at random times and may be right censored. If the test adequately differentiates between subjects who survive longer times and those who survive shorter times, this will assist clinical decisions. In this context, the concordance probability may support the assessment of precision medicine tools based on prognostic biomarkers models for overall survival. Definitions of time-dependent sensitivity and specificity are reviewed. Some connections between such definitions and concordance measures are also reviewed and we establish new connections via new measures of global concordance. We explore the relationship between such measures and their corresponding time-dependent AUC. To illustrate these concepts, an application in the context of Alzheimer's disease is presented.

Interictal spike networks predict surgical outcome in patients with drug-resistant focal epilepsy.

ObjectiveTo determine if properties of epileptic networks could be delineated using interictal spike propagation seen on stereo‐electroencephalography (SEEG) and if these properties could predict surgical outcome in patients with drug‐resistant epilepsy.MethodsWe studied the SEEG of 45 consecutive drug‐resistant epilepsy patients who underwent subsequent epilepsy surgery: 18 patients with good post‐surgical outcome (Engel I) and 27 with poor outcome (Engel II–IV). Epileptic networks were derived from interictal spike propagation; these networks described the generation and propagation of interictal epileptic activity. We compared the regions in which spikes were frequent and the regions responsible for generating spikes to the area of resection and post‐surgical outcome. We developed a measure termed source spike concordance, which integrates information about both spike rate and region of spike generation.ResultsInclusion in the resection of regions with high spike rate is associated with good post‐surgical outcome (sensitivity = 0.82, specificity = 0.73). Inclusion in the resection of the regions responsible for generating interictal epileptic activity independently of rate is also associated with good post‐surgical outcome (sensitivity = 0.88, specificity = 0.82). Finally, when integrating the spike rate and the generators, we find that the source spike concordance measure has strong predictability (sensitivity = 0.91, specificity = 0.94).InterpretationsEpileptic networks derived from interictal spikes can determine the generators of epileptic activity. Inclusion of the most active generators in the resection is strongly associated with good post‐surgical outcome. These epileptic networks may aid clinicians in determining the area of resection during pre‐surgical evaluation.