279 research outputs found
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No full textHenrik Toft SørensenDepartment of Clinical Epidemiology, Aarhus University Hospital, Aarhus N, DenmarkClinical Epidemiology has published more than 100 papers since its start in 2009, and the journal has been indexed in PubMed. This is an expression of the journal’s positive development. It emphasizes the need for a journal focusing on clinical epidemiology in a broad context, which is able to publish important papers quickly, following a thorough peer-review process. &nbsp
Pseudo-differential operators with isotropic symbols, Wick and anti-Wick operators, and hypoellipticity
Get PDFWe study the link between ilidos and Wick operators via the Bargmann transform. We deduce a formula for the symbol of the Wick operator in terms of the short-time Fourier transform of the Weyl symbol. This gives characterizations of Wick symbols of ilidos of Shubin type and of infinite order, and results on composition. We prove a series expansion of Wick operators in terms of anti-Wick operators which leads to a sharp Garding inequality and transition of hypoellipticity between Wick and Shubin symbols. Finally we show continuity results for anti-Wick operators, and estimates for the Wick symbols of anti-Wick operators.(c) 2022 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
The magnetoelectric effect in LiFePO4 - revisited
Get PDFWe study the magnetoelectric effect in LiFePO4 using the pyrocurrent method to determine the magnetic -field-induced electric polarization as a function of temperature for various applied magnetic field strengths. We discover a diagonal magnetoelectric tensor element not previously reported. This new coupling reflects the emergence of an electric polarization along a induced by a magnetic field along the same direction and is consistent with the symmetry-imposed requirements for the small canting components of the magnetic ground state reported for this compound. Our observation is thus further evidence for a ground state which is not supported by the space group Pnma as originally assigned to LiFePO4.This article is published as Fogh, Ellen, Bastian Klemke, Alexandre Pages, Jiying Li, David Vaknin, Henrik M. Rønnow, Niels B. Christensen, and Rasmus Toft-Petersen. "The magnetoelectric effect in LiFePO4–revisited." Physica B: Condensed Matter 648 (2023): 414380.
DOI: 10.1016/j.physb.2022.414380.
Copyright 2022 The Author(s).
Attribution 4.0 International (CC BY 4.0).
Posted with permission.
DOE Contract Number(s): AC02-07CH11358; 81045
Detection of colorectal cancer in symptomatic outpatients without visible rectal bleeding: Validity of the fecal occult blood test
No full textNiels Christian Bjerregaard1, Anders Tøttrup1, Henrik Toft Sørensen2, Søren Laurberg11Department of Surgery P, Aarhus Sygehus, Aarhus University Hospital, Tage-Hansens Gade 2, 8000 Aarhus C, Denmark; 2Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, 8200 Aarhus N, DenmarkBackground: In 2002, a new diagnostic strategy in symptomatic outpatients without known established colorectal cancer risk factors aged 40 years or older was implemented in Denmark. Fecal occult blood test (Hemoccult Sensa®) was a part of that strategy in patients without visible rectal bleeding.Aims: The aim was to assess the validity of the Hemoccult Sensa® test in detecting colorectal cancer in the above-mentioned outpatients.Patients: Symptomatic outpatients without known established colorectal cancer risk factors and without visible rectal bleeding.Methods: Hemoccult Sensa® was performed before endoscopic examination. Colorectal cancer was identified at histopathological examination. Patients completed a questionnaire about their symptoms before their first hospital appointment.Results: Eight of 256 patients were found to have colorectal cancer. Median patient age was 63 years. The positive predictive value, negative predictive value, sensitivity, and specificity of Hemoccult Sensa® for colorectal cancer were 10.5% (95% confidence interval [CI]: 6.8–14.3), 99.0% (95% CI: 97.8–100.0), 75.0% (95% CI: 69.7–80.3), and 79.4% (95% CI: 74.5–84.4).Conclusions: Hemoccult Sensa® as the initial examination in symptomatic outpatients without known established colorectal cancer risk factors presenting without rectal bleeding has to be used with caution. We did not find Hemoccult Sensa® test to be an acceptable alternative to flexible sigmoidoscopy.Keywords: colorectal neoplasms, occult blood, diagnostic tests, sensitivity, specificit
Positive predictive values of the International Classification of Disease, 10th edition diagnoses codes for diverticular disease in the Danish National Registry of Patients
No full textRune Erichsen1, Lisa Strate2, Henrik Toft Sørensen1, John A Baron31Department of Clinical Epidemiology, Aarhus University Hospital, Denmark; 2Division of Gastroenterology, University of Washington, Seattle, WA, USA; 3Departments of Medicine and of Community and Family Medicine, Dartmouth Medical School, NH, USAObjective: To investigate the accuracy of diagnostic coding for diverticular disease in the Danish National Registry of Patients (NRP).Study design and setting: At Aalborg Hospital, Denmark, with a catchment area of 640,000 inhabitants, we identified 100 patients recorded in the NRP with a diagnosis of diverticular disease (International Classification of Disease codes, 10th revision [ICD-10] K572–K579) during the 1999–2008 period. We assessed the positive predictive value (PPV) as a measure of the accuracy of discharge codes for diverticular disease using information from discharge abstracts and outpatient notes as the reference standard.Results: Of the 100 patients coded with diverticular disease, 49 had complicated diverticular disease, whereas 51 had uncomplicated diverticulosis. For the overall diagnosis of diverticular disease (K57), the PPV was 0.98 (95% confidence intervals [CIs]: 0.93, 0.99). For the more detailed subgroups of diagnosis indicating the presence or absence of complications (K573–K579) the PPVs ranged from 0.67 (95% CI: 0.09, 0.99) to 0.92 (95% CI: 0.52, 1.00). The diagnosis codes did not allow accurate identification of uncomplicated disease or any specific complication. However, the combined ICD-10 codes K572, K574, and K578 had a PPV of 0.91 (95% CI: 0.71, 0.99) for any complication.Conclusion: The diagnosis codes in the NRP can be used to identify patients with diverticular disease in general; however, they do not accurately discern patients with uncomplicated diverticulosis or with specific diverticular complications.Keywords: diverticulum, colon, diverticulitis, validation studie
Using registries to identify type 2 diabetes patients
No full textReimar W Thomsen, Henrik Toft Sørensen Department of Clinical Epidemiology, Aarhus University Hospital, DenmarkValidation studies of health care registries are considered boring by some. An epidemiologist recently conducted a validation study based on the Danish National Registry of Patients and received the following unflattering comment from a reviewer: “A good example of a paper of limited scope that probably would only be published electronically where space is unlimited”. We do not subscribe to this point of view. See Original Research articl
Antipsychotics and risk of venous thromboembolism: A population-based case-control study
No full textAnna K Jönsson1, Erzsebet Horváth-Puhó2, Staffan Hägg3, Lars Pedersen4, Henrik Toft Sørensen41Nordic School of Public Health, Gothenburg, Sweden; 2Centre for Registry Research, Aarhus C, Denmark; 3Division of Clinical Pharmacology, Linköping University, Linköping, Sweden; 4Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus C, DenmarkAbstract: During the last decade, the risk of venous thromboembolism (VTE) has been reported in users of antipsychotic drugs. However, the reports have been inconclusive. This study aimed to determine the relative risk of VTE in antipsychotic drug users. Using data from medical databases in North Jutland and Aarhus Counties, Denmark, and the Danish Civil Registration System, we identified 5,999 cases with a first-time diagnosis of VTE and, based on risk set sampling, 59,990 sex- and age-matched population controls during 1997–2005. Users of antipsychotic drugs were identified from population-based prescription databases and categorized based on filled prescriptions prior to admission date for VTE or index date for controls as current (at least one prescription within 90 days), recent (at least one prescription within 91–180 days), former (at least one prescription within 181–365 days) or nonusers (no recorded prescription within 365 days). Compared with nonusers, current users of any antipsychotic drugs had an increased risk of VTE (adjusted relative risk [ARR]: 1.99, 95% confidence interval [CI]: 1.69–2.34). Former users of any antipsychotic drugs had a nonsignificant elevated risk of VTE compared with nonusers (ARR: 1.54, 95% CI: 0.99–2.40, p-value: 0.056). In conclusion, users of antipsychotic drugs have an increased risk of VTE, compared with nonusers, which might be due to the treatment itself, to lifestyle factors, to the underlying disease, or to residual confounding. Keywords: antipsychotic agents, venous thromboembolism, adverse effects, case-control stud
Obituary – Anders Ekbom
No full textJonas F Ludvigsson,1 Johan Askling,1 Sven Cnattingius,1 Per Hall,1 Lars Klareskog,1 Olof Nyren,1 John A Baron,2 Henrik Toft Sørensen3 1Karolinska Institutet, Solna, Sweden; 2University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; 3Aarhus University, Aarhus, DenmarkCorrespondence: Jonas F Ludvigsson, Email [email protected]
Structured approach to design of diagnostic test evaluation studies for chronic progressive infections in animals
No full textDiagnostic test evaluations (DTEs) for chronic infections are challenging because a protracted incubation period has to be considered in the design of the DTE, and the adverse effects of infection may be widespread and progressive over an animal's entire life. Frequently, the specific purpose of the test is not formally considered when a test is evaluated. Therefore, the result is often a DTE where test sensitivity and specificity estimates are biased, either because of problems with establishing the true infection status or because the test detects another aspect of the infection (and analyte) than originally intended. The objective of this paper is to outline a structured approach to the design and conduct of a DTE for diagnostic tests used for chronic infections in animals, and intended for different purposes. We describe the process from reflections about test purpose and the underlying target condition through considerations of the pathogenesis, and specification of a practical case definition, which can subsequently be used in the DTE for the specific purpose. The process is illustrated by two examples of Mycobacterium avium subsp. paratuberculosis (MAP) infections in cattle. MAP infections are chronic and can result in different adverse effects at different time points during the incubation period. The description provides input on the process and deductive reasoning which are integral parts to develop a high-quality design of a DTE for chronic infectious diseases.ID: S0378113511000381; M3: Article; Accession Number: S0378113511000381; Author: Søren Saxmose Nielsen (a, b, ⁎); Author: Nils Toft (a, b); Author: Ian Andrew Gardner (a, b); Affiliation: Department of Large Animal Sciences, Faculty of Life Sciences, University of Copenhagen, Grønnegårdsvej 8, DK-1870 Frederiksberg C, Denmark; Affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; Keyword: Chronic infectious diseases; Keyword: Design strategy; Keyword: Diagnostic test evaluation; Keyword: Paratuberculosis; Number of Pages: 11; Language: English
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