Detecting differential item functioning in 2PL multistage assessments

The detection of differential item functioning is crucial for the psychometric evaluation of multistage tests. This paper discusses five approaches presented in the literature: logistic regression, SIBTEST, analytical score-based tests, bootstrap score-based tests, and permutation score-based tests. First, using an simulation study inspired by a real-life large-scale educational assessment, we compare the five approaches with respect to their type I error rate and their statistical power. Then, we present an application to an empirical data set. We find that all approaches show type I error rates close to the nominal alpha level. Furthermore, all approaches are shown to be sensitive to uniform and non-uniform DIF effects, with the score-based tests showing the highest power

High-density lipoprotein cholesterol, coronary artery disease, and cardiovascular mortality

Aims High-density lipoprotein (HDL) cholesterol is a strong predictor of cardiovascular mortality. This work aimed to investigate whether the presence of coronary artery disease (CAD) impacts on its predictive value. Methods and results We studied 3141 participants (2191 males, 950 females) of the LUdwigshafen RIsk and Cardiovascular health (LURIC) study. They had a mean ± standard deviation age of 62.6 ± 10.6 years, body mass index of 27.5 ± 4.1 kg/m², and HDL cholesterol of 38.9 ± 10.8 mg/dL. The cohort consisted of 699 people without CAD, 1515 patients with stable CAD, and 927 patients with unstable CAD. The participants were prospectively followed for cardiovascular mortality over a median (inter-quartile range) period of 9.9 (8.7-10.7) years. A total of 590 participants died from cardiovascular diseases. High-density lipoprotein cholesterol by tertiles was inversely related to cardiovascular mortality in the entire cohort (P = 0.009). There was significant interaction between HDL cholesterol and CAD in predicting the outcome (P = 0.007). In stratified analyses, HDL cholesterol was strongly associated with cardiovascular mortality in people without CAD [3rd vs. 1st tertile: HR (95% CI) = 0.37 (0.18-0.74), P = 0.005], but not in patients with stable [3rd vs. 1st tertile: HR (95% CI) = 0.81 (0.61-1.09), P = 0.159] and unstable [3rd vs. 1st tertile: HR (95% CI) = 0.91 (0.59-1.41), P = 0.675] CAD. These results were replicated by analyses in 3413 participants of the AtheroGene cohort and 5738 participants of the ESTHER cohort, and by a meta-analysis comprising all three cohorts. Conclusion The inverse relationship of HDL cholesterol with cardiovascular mortality is weakened in patients with CAD. The usefulness of considering HDL cholesterol for cardiovascular risk stratification seems limited in such patient

The role of magnetic anisotropy in the Kondo effect

In the Kondo effect, a localized magnetic moment is screened by forming a correlated electron system with the surrounding conduction electrons of a non-magnetic host. Spin S=1/2 Kondo systems have been investigated extensively in theory and experiments, but magnetic atoms often have a larger spin. Larger spins are subject to the influence of magnetocrystalline anisotropy, which describes the dependence of the magnetic moment's energy on the orientation of the spin relative to its surrounding atomic environment. Here we demonstrate the decisive role of magnetic anisotropy in the physics of Kondo screening. A scanning tunnelling microscope is used to simultaneously determine the magnitude of the spin, the magnetic anisotropy and the Kondo properties of individual magnetic atoms on a surface. We find that a Kondo resonance emerges for large-spin atoms only when the magnetic anisotropy creates degenerate ground-state levels that are connected by the spin flip of a screening electron. The magnetic anisotropy also determines how the Kondo resonance evolves in a magnetic field: the resonance peak splits at rates that are strongly direction dependent. These rates are well described by the energies of the underlying unscreened spin states.Comment: 14 pages, 4 figures, published in Nature Physic

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Detecting Differential Item Functioning in 2PL Multistage Assessments

The detection of differential item functioning is crucial for the psychometric evaluation of multistage tests. This paper discusses five approaches presented in the literature: logistic regression, SIBTEST, analytical score-based tests, bootstrap score-based tests, and permutation score-based tests. First, using an simulation study inspired by a real-life large-scale educational assessment, we compare the five approaches with respect to their type I error rate and their statistical power. Then, we present an application to an empirical data set. We find that all approaches show type I error rates close to the nominal alpha level. Furthermore, all approaches are shown to be sensitive to uniform and non-uniform DIF effects, with the score-based tests showing the highest power

vMedical error analysis in dermatology according to the reports of the North Rhine Medical Association from 2004 to 2018

Zusammenfassung HintergrundDie von der Gutachterkommission fur arztliche Behandlungsfehler bei der Arztekammer Nordrhein begutachteten Behandlungsfehlervorwurfe ermoglichen die Identifikation von Qualitatssicherungsproblemen in der Patientenversorgung. Methodik333 dermatologische Begutachtungen (Gutachten) aus den Abschlussjahren 2004-2018 wurden analysiert. Um Veranderungen im zeitlichen Verlauf hinsichtlich der Gutachtenanzahl (kumulativ oder indikationsbezogen) abzubilden, erfolgte eine Zuordnung in drei Funf-Jahres-Intervalle. Weiterhin wurden die Gutachten im Hinblick auf die Versorgungsarten, definierte Diagnosekategorien und therapeutische Interventionen betrachtet. Die statistisch-deskriptive Analyse erfolgte mit SPSS 27. Einzelne relevante Gutachtenfalle werden kasuistisch naher erlautert. ErgebnisseDie Anzahl dermatologischer Gutachten ist von 119 im ersten auf 92 Gutachten im letzten Funf-Jahres-Intervall gesunken einhergehend mit rucklaufigen Behandlungsfehlerquoten (43 % und 29 %) trotz fachubergreifend steigender Verfahrensanzahl. 104 Gutachten bezogen sich auf (vermeintliche) Diagnostikfehler, 156 auf physikalische oder pharmakologische Therapien und 73 auf operative Therapien. Letztere wiesen eine niedrige Behandlungsfehlerquote auf (29 %). SchlussfolgerungenGemessen an der Zahl der dermatologischen Behandlungsfalle in Deutschland werden Patientenvorwurfe nur sehr selten erhoben und belegen moglicherweise eine gro ss ere Patientenzufriedenheit und/oder ein geringeres Risikopotenzial dermatologischer Behandlungen im Vergleich zu anderen Fachbereichen. Fehlerhafte Dosierungen oder Gerateeinstellungen stellen ebenso wie Aufklarungs- und Befunderhebungsfehler relevante Fehlerquellen dar. Die dargestellten Kasuistiken zeigen Fehlerquellen auf und sollen dazu beitragen zukunftige Behandlungsfehler zu vermeiden

Medical error analysis in dermatology according to the reports of the North Rhine Medical Association from 2004 to 2018

BackgroundAssessment of complaints addressed to the Expert Committee for Medical Malpractice Claims of the North Rhine Medical Association helps to identify quality assurance problems in dermatology. Methods333 dermatological reports (years 2004-2018) were allocated to three five-year intervals in order to show changes of total number of reports and with regard to indications, types of care, defined diagnosis categories, and therapeutic interventions. Statistical analysis was mainly descriptive (SPSS 27). Representative cases are explained in more detail. ResultsThe number of dermatological reports fell from 119 in the first to 92 reports in the last five-year interval, along with a decline in treatment error rates (43 % and 29 %) despite an increasing number of procedures across disciplines. 104 reports dealt with (supposed) diagnostic errors, 156 with physical or pharmacological therapies, and 73 reports with surgery. The latter had a low treatment error rate (29 %). ConclusionsIn comparison to the number of dermatological treatments in Germany, patient allegations are raised only rarely indicating greater patient satisfaction and/or a lower risk potential in dermatology. Incorrect dosages or device settings, diagnostic errors, and deficits in obtaining informed consent are relevant sources of error as underlined by the presented case reports