Percentile-based Approach Research Articles

Defining Echocardiographic Degrees of Right Heart Size and Function in Pulmonary Vascular Disease From the PVDOMICS Study

BACKGROUND: Defining qualitative grades of echocardiographic metrics of right heart chamber size and function is critical for screening, clinical assessment, and measurement of therapeutic response in individuals with pulmonary vascular disease (PVD). In a population enriched for PVD, we sought to establish qualitative grades and prognostic value of right heart chamber size and function. METHODS: We investigated 1053 study participants in PVDOMICS (Redefining Pulmonary Hypertension Through the PVD Phenomics Program) to determine clinical and echocardiographic differences associated with increasing pulmonary vascular resistance severity. Right heart chamber size and function were qualitatively assessed using a percentile-based approach above the median values to create a clinical grading system for right heart adaptation. The relationship between echocardiographic categories and all-cause mortality was examined using survival analyses adjusted for potential confounders. RESULTS: A stepwise increase in adverse right heart remodeling was observed with a concomitant decrease in functional parameters by pulmonary vascular resistance strata ( P <0.001 for all). Mild, moderate, and severe categories of right heart chamber size and dysfunction were defined using a percentile-based approach across the spectrum of PVD. During a median follow-up of 2.07 years (interquartile range, 1.23–3.01 years), 130 participants died (11.4%). Progressive pulmonary vascular resistance increase and 2DE evidence of right heart dysfunction inclusive of fractional area change, and right ventricular global longitudinal strain were independently associated with increased all-cause mortality risk in multivariate analysis adjusted for age, disease duration, and male sex. CONCLUSIONS: In this well-characterized sample of adults with diverse etiologies and varying PVD severity, we define categories of abnormal right heart chamber size and function. Further, we demonstrate a stepwise relationship between these categories of abnormal morphology and function and all-cause mortality. Defining grades of right ventricular dysfunction in individuals with known PVD has important clinical implications for monitoring disease progression and response to therapies.

DSC-PWI presurgical differentiation of grade 4 astrocytoma and glioblastoma in young adults: rCBV percentile analysis across enhancing and non-enhancing regions

PurposeThe presurgical discrimination of IDH-mutant astrocytoma grade 4 from IDH-wildtype glioblastoma is crucial for patient management, especially in younger adults, aiding in prognostic assessment, guiding molecular diagnostics and surgical planning, and identifying candidates for IDH-targeted trials. Despite its potential, the full capabilities of DSC-PWI remain underexplored. This research evaluates the differentiation ability of relative-cerebral-blood-volume (rCBV) percentile values for the enhancing and non-enhancing tumor regions compared to the more commonly used mean or maximum preselected rCBV values.MethodsThis retrospective study, spanning 2016–2023, included patients under 55 years (age threshold based on World Health Organization recommendations) with grade 4 astrocytic tumors and known IDH status, who underwent presurgical MR with DSC-PWI. Enhancing and non-enhancing regions were 3D-segmented to calculate voxel-level rCBV, deriving mean, maximum, and percentile values. Statistical analyses were conducted using the Mann-Whitney U test and AUC-ROC.ResultsThe cohort consisted of 59 patients (mean age 46; 34 male): 11 astrocytoma-4 and 48 glioblastoma. While glioblastoma showed higher rCBV in enhancing regions, the differences were not significant. However, non-enhancing astrocytoma-4 regions displayed notably higher rCBV, particularly in lower percentiles. The 30th rCBV percentile for non-enhancing regions was 0.705 in astrocytoma-4, compared to 0.458 in glioblastoma (p = 0.001, AUC-ROC = 0.811), outperforming standard mean and maximum values.ConclusionEmploying an automated percentile-based approach for rCBV selection enhances differentiation capabilities, with non-enhancing regions providing more insightful data. Elevated rCBV in lower percentiles of non-enhancing astrocytoma-4 is the most distinguishable characteristic and may indicate lowly vascularized infiltrated edema, contrasting with glioblastoma’s pure edema.

Pitfalls in diagnosing temperature extremes

Worsening temperature extremes are among the most severe impacts of human-induced climate change. These extremes are often defined as rare events that exceed a specific percentile threshold within the distribution of daily maximum temperature. The percentile-based approach is chosen to follow regional and seasonal temperature variations so that extremes can occur globally and in all seasons, and frequently uses a running seasonal window to increase the sample size for the threshold calculation. Here, we show that running seasonal windows as used in many studies in recent years introduce a time-, region-, and dataset-depended bias that can lead to a striking underestimation of the expected extreme frequency. We reveal that this bias arises from artificially mixing the mean seasonal cycle into the extreme threshold and propose a simple solution that essentially eliminates it. We then use the corrected extreme frequency as reference to show that the bias also leads to an overestimation of future heatwave changes by as much as 30% in some regions. Based on these results we stress that running seasonal windows should not be used without correction for estimating extremes and their impacts.

Still no Dunning-Kruger effect: A reply to Hiller

The primary criticism raised by Hiller (2023) pertained to the transformation of the self-assessed intelligence (SAI) scores applied by Gignac and Zajenkowski (2020), an investigation that suggested the Dunning-Kruger effect (DKE) may be primarily a statistical artefact. Hiller recommended an alternative transformation. Our re-analysis of Gignac and Zajenkowski's data with Hiller's recommended transformation failed to find evidence in favour of the DK hypothesis. Hiller also recommended SAI measurement with a percentile-based approach. Based on a review of the literature, one investigation has employed a percentile-based approach to SAI measurement, and it largely failed to support the DK hypothesis, when analysed with the non-linear regression approach recommended by Gignac and Zajenkowski. We conclude by encouraging researchers to continue to derive novel approaches to testing the DK hypothesis, especially approaches that overcome known methodological challenges.

Exponentially weighted moving average Lepage-type schemes based on the lower-order percentile of the run-length metrics and their use in monitoring time-occupancy in Google applications

ABSTRACT Many existing monitoring schemes in the literature are based on the in-control (IC) average or median run-length. Several Phase-II schemes frequently fail to protect against the high rate of early false alarms. The problem may worsen when the average run-length metric is used, and the scheme is based on unknown and estimated parameters. Early false alarms can be avoided using monitoring schemes based on the lower-order percentiles of the IC run-length distribution. The exponentially weighted moving average (EWMA)-Lepage scheme is presented in this paper. The new design is based on a percentile-based approach that can effectively reduce and control the rate of early false alarms. The run-length properties of the EWMA scheme with the lower-order percentile-based design were investigated and compared with the double EWMA-Lepage and homogeneously weighted moving average-Lepage schemes. Detailed simulation studies show no clear winner among the three schemes for given sample sizes for the unknown shift. Instead, the size of the Phase-I and Phase-II samples heavily influences the choice of a potentially beneficial scheme. A case study on monitoring the time occupation of users on the Google application is presented to demonstrate the design and implementation of lower-percentile-based techniques. Some future research directions are offered.

THE BALTIMORE LONGITUDINAL STUDY OF AGING: READY TO SHARE

Abstract Beginning January 2023, the new National Institutes of Health (NIH) Data Sharing Policy for NIH-funded and conducted research is scheduled to go into effect. In anticipation of this requirement, scientists and staff of the Baltimore Longitudinal Study of Aging (BLSA) launched a comprehensive effort to create a user friendly well-documented accessible database scheduled for a “soft” release just in time for GSA. The BLSA, established in 1958 to study normative aging, continues to advance knowledge and understanding of aging mechanisms and their impact on and response to disease processes. During a 3-day clinic visit, the 1200+ BLSA participants undergo comprehensive evaluation covering the full range of physical functional and cognitive performance capacity as well as extensive imaging studies, biological sample collection and clinical examination. In this symposium, Dr. Griswold will introduce the data sharing platform and demonstrate its facility. Dr. Simonsick will elaborate on development of a fitness percentile-based approach to define exceptional aging and the factors associated with maintaining exceptional status. Dr. Moore will provide findings on life-course physical activity and CT derived muscle parameters and homeostatic regulation in later life. Dr. Tian will share her ongoing work aimed at identifying metabolomic signatures of brain atrophy and Alzheimer’s disease risk. Dr. Tanaka will report on her work analyzing the metabolomic profile of different dietary patterns and their association with frailty. Our Discussant, Dr. Ferrucci will briefly share future directions for the BLSA and then invite attendees to comment on the BLSA data sharing platform and scientific priorities.

ЗАСТОСУВАННЯ СТАТИСТИЧНИХ ПРИЙОМІВ У ПРАКТИЦІ ПОБУДОВИ ШКАЛИ ЙМОВІРНОСТІ ДЕФОЛТУ

Анотація. Обґрунтовано основні характерні властивості кривої PD (Probabilityofdefault), що сформувалися у практиці моделювання. Доведено, що основними характеристиками кривої PD є те, що вона ґрунтуватися на даних про фактичну відносну частоту дефолтів у кожному з ризик-класів за обраний період часу і має форму, що апроксимує або збігається з експонеційнійною функцією. Показано, що важливим аспектом, який впливає на калібрування, є кількість рейтингових класів і способи їх побудови. Визначено, що нахил кривої демонструє класифікаційну ефективність моделі. Для моделей із високими дискримінаторними властивостями характерна форма кривої, що має повільне зростання в рейтингових класах верхньої частини шкали і значне пришвидшення зростання в останніх класах ризику. Проаналізовано два основних підходи до визначення кількості класів ризику: підхід на основі процентіліві підхід на основі рівних діапазонів балів. Показано, що при формуванні класів варто враховувати загальний обсяг вибіркових спостережень, пропорцію «хороших» і «поганих» та обирати кількість класів таким чином, щоб воно було не надто велике і не надто мале. Доведено, що на практики калібрування впливають дані, мета та обмеження дослідження. На практичних прикладах розглянуто застосування методу найменших квадратів і методу екстраполяції. Метод найменших квадратів, і зокрема похідний метод екстраполяції, дозволяють будувати калібраційну криву на основі даних про відносну частоту дефолтів. Визначено, що математичний апарат сімейства нелінійних кривих дозволяє моделювати процес експоненційного зростання з різним рівнем інтенсивності. Експоненційна крива і споріднені з нею функції можуть бути корисними при моделюванні більш консервативних оцінок PD або для моделей з високими дискримінаційними властивостями, у той час як функція Вейбулла, S-крива і степенева функція можуть краще пристосовуватися до процесів помірного зростання. Застосування практичних прийомів побудови шкали PD є важливим для багатьох вітчизняних банківських спеціалістів, хто займається внутрішніми моделями кредитного ризику. Ключові слова:калібрування, дефолт, імовірність, криві, калібрація кривої ймовірності дефолту, метод найменших квадратів, метод екстраполяції. Формул: 21; рис.: 1; табл.: 7; бібл.: 10.

Relationship between rock physical properties and spectral mineralogy applied to exploration for an unconformity-related uranium deposit (Saskatchewan, Canada)

Infrared (IR) spectroscopy has been used to characterize clay and clay-sized minerals present in drill cores that are associated with unconformity-related uranium deposits. Physical properties have been measured on samples to gain empirical data about the rock types and associated relationships with geophysical survey data. These data can be used to build three-dimensional geological models and constrain geophysical inversions. The objective of this study is to verify whether a relationship exists between rock physical properties and IR spectral mineralogy. Physical properties were measured on 427 core samples collected from the Martin Lake project, which is located in the southeastern Athabasca Basin (Saskatchewan, Canada). Results indicate that resistivity, density, and porosity are correlated to each other, especially within basement units. A comparison of their distribution with the IR spectral mineralogy demonstrates a relationship for each altered and unaltered samples. The samples with low resistivity and density, and high porosity are characterized by the presence of a di-trioctahedral (Al–Mg) chlorite (sudoite) due to the hydrothermal alteration processes. The unaltered samples with higher resistivity and density, and low porosity contain a tri-octahedral (Fe–Mg) chlorite as a result of metamorphic processes. Eleven mineralogical classes can be established based on IR spectroscopy. A percentile-based approach has been proposed and tested to define physical property ranges for each of the classes to predict resistivity and density values downhole.

Background Variation and Threshold Values for Cadmium Concentration in Terra Rossa Soil from Dalmatia, Croatia

The objectives of this study were to (i) establish the background variation and determine a threshold values for aqua regia soluble cadmium (Cd) in Terra Rossa soil at the local scale (Dalmatia, Croatia), (ii) check for possible soil Cd enrichment comparing its concentration at two different depths, and (iii) compare the threshold values for Cd calculated applying different statistical techniques with soil guideline values (SGV) as defined in Croatia and other national systems in Europe. The four statistical methods (the mean ± 2 standard deviations [mean ± 2SD], the median ± 2 median absolute deviations [median ± 2MAD], the (upper) Tukey inner fence (TIF), and the percentile-based approach) were used to establish the threshold values for Cd and identify samples with high Cd concentrations deviating from the background variation in a studied dataset. Overall, 74 samples from the A horizon of Terra Rossa soil were analyzed for aqua regia soluble Cd concentration (CdA); major soil properties—pH, CaCO3, soil organic carbon (SOC) content, P2O5, K2O, and particle-size distribution—were also determined in these samples. The underlying cambic B horizon was analyzed only for Cd concentration (CdB) The median CdA and CdB values of 1.84 and 1.70 mg kg–1, respectively as well as the maximum value of 8.53 mg kg–1 in the A horizon and 7.56 mg kg–1 in the B horizon obtained in this study attested to anomalously high Cd concentrations. The median CdA/CdB ratio was close to unity (1.07) indicating very low Cd enrichment in the A horizon. The [median ± 2MAD] method achieved the lowest threshold Cd value of 4.68 mg kg–1 and, consequently, a maximum number of outliers; it was followed by the classical [mean ± 2SD] method (5.01 mg kg–1), the Q95th percentile (5.29 mg kg–1), the Q98th percentile (5.64 mg kg–1), and the TIF method with the highest threshold value of 6.93 mg kg–1. All specified threshold values for Cd concentration repeatedly exceeded the maximum admissible concentrations (MACv) for agricultural land as defined in soil guideline values developed in Croatia and in several countries of the European Union. These findings indicate that more attention should be paid to the unusually high Cd concentrations in Terra Rossa soils originating from the natural sources; a more detailed geochemical survey of these soils should be performed in the future.

The human cost of global warming: Deadly landslides and their triggers (1995–2014)

Worldwide, landslides incur catastrophic and significant economic and human losses. Previous studies have characterized the patterns in landslides' fatalities, from all kinds of triggering causes, at a continental or global scale, but they were based on data from periods of <10 years. The research herein presented hypothesizes that climate change associated with extreme rainfall and population distribution is contributing to a higher number of deadly landslides worldwide. This study maps and identified deadly landslides in 128 countries and it encompasses their role, for a 20 years' period from January/1995 to December/2014, considered representative for establishing a relationship between landslides and their meteorological triggers. A database of georeferenced landslides, their date, and casualties' information, duly validated, was implemented. A hot spot analysis for the daily record of landslide locations was performed, as well as a percentile-based approach to evaluate the trend of extreme rainfall events for each occurrence. The relationship between casualty, population distribution, and rainfall was also evaluated. For 20 years, 3876 landslides caused a total of 163,658 deaths and 11,689 injuries globally. They occurred most frequently between June and December in the Northern Hemisphere, and between December and February in the Southern Hemisphere. A significant global rise in the number of deadly landslides and hotspots across the studied period was observed. Analysis of daily rainfall confirmed that more than half of the events were in areas exposed to the risk of extreme rainfall. The relationships established between extreme rainfall, population distribution, seasonality, and landslides provide a useful basis for efforts to model the adverse impacts of extreme rainfall due to climate change and human activities and thus contribute towards a more resilient society.

Technological research in the EU is less efficient than the world average. EU research policy risks Europeans’ future

We have studied the efficiency of research in the EU by a percentile-based citation approach that analyzes the distribution of country papers among the world papers. Going up in the citation scale, the frequency of papers from efficient countries increases while the frequency from inefficient countries decreases. In the percentile-based approach, this trend, which is uniform at any citation level, is measured by the e(p) index that equals the P-top 1%/P-top 10% ratio. By using the ep index we demonstrate that EU research on fast-evolving technological topics is less efficient than the world average and that the EU is far from being able to compete with the most advanced countries. The ep index also shows that the USA is well ahead of the EU in both fast- and slow-evolving technologies, which suggests that the advantage of the USA over the EU in innovation is due to low research efficiency in the EU. In accord with some previous studies, our results show that the European Commission's ongoing claims about the excellence of EU research are based on a wrong diagnosis. The EU must focus its research policy on the improvement of its inefficient research. Otherwise, the future of Europeans is at risk. (C) 2018 Elsevier Ltd. All rights reserved.

Using subject-specific three-dimensional (3D) anthropometry data in digital human modelling: case study in hand motion simulation

Digital human modelling enables ergonomists and designers to consider ergonomic concerns and design alternatives in a timely and cost-efficient manner in the early stages of design. However, the reliability of the simulation could be limited due to the percentile-based approach used in constructing the digital human model. To enhance the accuracy of the size and shape of the models, we proposed a framework to generate digital human models using three-dimensional (3D) anthropometric data. The 3D scan data from specific subjects’ hands were segmented based on the estimated centres of rotation. The segments were then driven in forward kinematics to perform several functional postures. The constructed hand models were then verified, thereby validating the feasibility of the framework. The proposed framework helps generate accurate subject-specific digital human models, which can be utilised to guide product design and workspace arrangement.Practitioner Summary: Subject-specific digital human models can be constructed under the proposed framework based on three-dimensional (3D) anthropometry. This approach enables more reliable digital human simulation to guide product design and workspace arrangement.

Ranking institutions within a university based on their scientific performance: A percentile-based approach

Over the recent years, the subject of university rankings has attracted a significant amount of attention and sparked a scientific debate. However, few studies on this topic focus on elaborating the scientific performance of universities’ institutions, such as institutes, schools, and faculties. For this reason, the aim of this study is to design an appropriate framework for evaluating and ranking institutions within a university. The devised methodology ranks institutions based on the number of published papers, mean normalized citation score (MNCS), and four percentile-based indicators using the I-distance method. We applied the proposed framework and scrutinized the University of Belgrade (UB) as the biggest and the best-ranked university in Serbia. Thus, 31 faculties and 11 institutes were compared. Namely, an in-depth percentile-based analysis of the UB papers indexed in the Science Citation Index Expanded (SCIe) and the Social Science Citation Index (SSCI) for the period 2008-2011 is provided. The results clearly show considerable discrepancies in two occasions: first, when it comes to the question of leading author, and second, when it comes to analyzing the percentile rank classes (PRs) of groups of faculties.

Alert thresholds for monitoring environmental variables: A new approach applied to seagrass beds diversity in New Caledonia

Monitoring ecological variables is mandatory to detect abnormal changes in ecosystems. When the studied variables exceed predefined alert thresholds, management actions may be required. In the past, alert thresholds have been typically defined by expert judgments and descriptive statistics. Recently, approaches based on statistical power were also used. In New Caledonia, seagrass monitoring is a priority given their vulnerability to natural and anthropic disturbances. To define a suitable monitoring strategy and alert thresholds, we compared a Percentile Based Approach (PBA) and a sensitivity analysis of power (SAP). Both methods defined statistically relevant alert thresholds, but the SAP approach was more robust to spatial and temporal variability of seagrass cover. Moreover, this method characterized the sensitivity of threshold values to sampling efforts, a useful knowledge for managers.

Which percentile-based approach should be preferred for calculating normalized citation impact values? An empirical comparison of five approaches including a newly developed citation-rank approach (P100)

For comparisons of citation impacts across fields and over time, bibliometricians normalize the observed citation counts with reference to an expected citation value. Percentile-based approaches have been proposed as a non-parametric alternative to parametric central-tendency statistics. Percentiles are based on an ordered set of citation counts in a reference set, whereby the fraction of papers at or below the citation counts of a focal paper is used as an indicator for its relative citation impact in the set. In this study, we pursue two related objectives: (1) although different percentile-based approaches have been developed, an approach is hitherto missing that satisfies a number of criteria such as scaling of the percentile ranks from zero (all other papers perform better) to 100 (all other papers perform worse), and solving the problem with tied citation ranks unambiguously. We introduce a new citation-rank approach having these properties, namely P100; (2) we compare the reliability of P100 empirically with other percentile-based approaches, such as the approaches developed by the SCImago group, the Centre for Science and Technology Studies (CWTS), and Thomson Reuters (InCites), using all papers published in 1980 in Thomson Reuters Web of Science (WoS). How accurately can the different approaches predict the long-term citation impact in 2010 (in year 31) using citation impact measured in previous time windows (years 1–30)? The comparison of the approaches shows that the method used by InCites overestimates citation impact (because of using the highest percentile rank when papers are assigned to more than a single subject category) whereas the SCImago indicator shows higher power in predicting the long-term citation impact on the basis of citation rates in early years. Since the results show a disadvantage in this predictive ability for P100 against the other approaches, there is still room for further improvements.

The Statistical Basis for Serial Monitoring in Audiology

Audiologists regularly use serial monitoring to evaluate changes in a patient's auditory function over time. Observed changes are compared with reference standards to determine whether further clinical action is necessary. Reference standards are established in a control sample of otherwise healthy subjects to identify the range of auditory shifts that one might reasonably expect to occur in the absence of any pathological insult. Statistical approaches to this seemingly mundane problem typically invoke 1 of 3 approaches: percentiles of the cumulative distribution, the variance of observed shifts, and the "standard error of measurement." In this article, the authors describe the statistical foundation for these approaches, along with a mixed model-based alternative, and identify several necessary, although typically unacknowledged assumptions. Regression to the mean, the phenomenon of an unusual measurement typically followed by a more common one, can seriously bias observed changes in auditory function and clinical expectations. An approach that adjusts for this important effect is also described. Distortion product otoacoustic emissions (DPOAEs) elicited at a single primary frequency, f2 of 3175 Hz, were collected from 32 healthy subjects at baseline and 19 to 29 days later. Ninety percent test-retest reference limits were computed from these data using each statistical approach. DPOAE shifts were also collected from a sample of 18 cisplatin patients tested after 120 to 200 mg of cisplatin. Reference limits established according to each of the statistical approaches in the healthy sample were used to identify clinically alarming DPOAE shifts in the cisplatin patient sample. Reference limits established with any of the parametric methods were similar. The percentile-based approach gave the widest and least precisely estimated intervals. The highest sensitivity for detecting clinically alarming DPOAE shifts was based on a mixed model approach that adjusts for regression to the mean. Parametric methods give similar serial monitoring criteria as long as certain critical assumptions are met by the data. The most flexible method for estimating test-retest limits is based on the linear mixed model. Clinical sensitivity may be further enhanced by adjusting for regression to the mean.

Comparison of Per Cent Predicted and Percentile Values for Pulmonary Function Test Interpretation

Pulmonary function tests (PFTs) are commonly interpreted as a fraction of predicted normal values, with an abnormal test often defined as less than 80% or greater than 120% of the predicted value. However, recommendations of the American Thoracic Society/European Respiratory Society suggest using a percentile-based approach to define an abnormal test (less than the fifth or greater than the 95th percentiles). To compare PFT values obtained by the per cent predicted method with the percentile-based method for lung function parameters. Full PFTs performed between January 2000 and July 2004, at the Health Sciences Centre (Winnipeg, Manitoba) were analyzed. Using the Crapo and Gutierrez equations, per cent predicted and percentile values were calculated. An abnormal test was defined as less than 80% or greater than 120% of predicted (per cent predicted method) or as less than the fifth or greater than the 95th percentiles (percentile method). Using the percentile method as reference standard, the diagnostic test characteristics of the per cent predicted method were calculated. The full PFTs of 2176 men and 1658 women were analyzed using the Crapo and Gutierrez equations. The mean (+/- SD) age of all subjects was 52+/-15 years. Per cent agreement between the two tests was more than 94% for all parameters except for reduced residual volume (88%). Per cent predicted methods had suboptimal sensitivity for abnormal total lung capacity (88% to 89%), increased residual volume (83% to 89%) and reduced diffusion capacity (89% with Crapo equations). Suboptimal specificity (83% to 86%) was observed for decreased residual volume. The results of the per cent predicted and percentile-based approaches for PFT interpretation were similar for the majority of lung function parameters. These two methods can be used interchangeably for spirometry. However, caution may be warranted in relying solely on per cent predicted methods for assessing lung volume or diffusion capacity.