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  1. Article ; Online: A Simple-to-Use R Package for Mimicking Study Data by Simulations.

    Koliopanos, Giorgos / Ojeda, Francisco / Ziegler, Andreas

    Methods of information in medicine

    2023  Volume 62, Issue 3-04, Page(s) 119–129

    Abstract: Background: Data protection policies might prohibit the transfer of existing study data to interested research groups. To overcome legal restrictions, simulated data can be transferred that mimic the structure but are different from the existing study ... ...

    Abstract Background: Data protection policies might prohibit the transfer of existing study data to interested research groups. To overcome legal restrictions, simulated data can be transferred that mimic the structure but are different from the existing study data.
    Objectives: The aim of this work is to introduce the simple-to-use R package Mock Data Generation (modgo) that may be used for simulating data from existing study data for continuous, ordinal categorical, and dichotomous variables.
    Methods: The core is to combine rank inverse normal transformation with the calculation of a correlation matrix for all variables. Data can then be simulated from a multivariate normal and transferred back to the original scale of the variables. Unique features of modgo are that it allows to change the correlation between variables, to perform perturbation analysis, to handle multicenter data, and to change inclusion/exclusion criteria by selecting specific values of one or a set of variables. Simulation studies on real data demonstrate the validity and flexibility of modgo.
    Results: modgo mimicked the structure of the original study data. Results of modgo were similar with those from two other existing packages in standard simulation scenarios. modgo's flexibility was demonstrated on several expansions.
    Conclusion: The R package modgo is useful when existing study data may not be shared. Its perturbation expansion permits to simulate truly anonymized subjects. The expansion to multicenter studies can be used for validating prediction models. Additional expansions can support the unraveling of associations even in large study data and can be useful in power calculations.
    MeSH term(s) Computer Simulation ; Computer Security
    Language English
    Publishing date 2023-03-07
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 3500-2
    ISSN 2511-705X ; 0026-1270
    ISSN (online) 2511-705X
    ISSN 0026-1270
    DOI 10.1055/a-2048-7692
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  2. Article ; Online: New race-free creatinine- and cystatin C-based equations for the estimation of glomerular filtration rate and association with cardiovascular mortality in the AtheroGene study.

    Ntaios, George / Brederecke, Jan / Ojeda, Francisco M / Zeller, Tanja / Blankenberg, Stefan / Schnabel, Renate B

    Internal and emergency medicine

    2024  Volume 19, Issue 3, Page(s) 697–703

    Abstract: Renal function is associated with cardiovascular outcomes and mortality. Among equations used to eGFR, CKD-EPI equations show more accurate association with cardiovascular risk and mortality than MDRD. Recently, new CKD-EPI equations were proposed which ... ...

    Abstract Renal function is associated with cardiovascular outcomes and mortality. Among equations used to eGFR, CKD-EPI equations show more accurate association with cardiovascular risk and mortality than MDRD. Recently, new CKD-EPI equations were proposed which do not include race and would be considered sufficiently accurate to estimate eGFR in clinical practice. It is unknown if these new race-free equations are comparably well associated with cardiovascular outcomes in high-risk individuals. The analysis was performed in the AtheroGene Study cohort including patients at high cardiovascular risk. eGFR was determined using the established as well as the recently developed formulas which are calculated without the otherwise existing coefficient for black race. The outcome was cardiovascular death. Analyses included Cox-proportional hazard regression and area-under-the-curve calculation. The analysis included 2089 patients followed up for a median of 3.8 years with a maximum of 6.9 years, corresponding to an overall period of 7701 patient-years. Cardiovascular death occurred in 93 (4.45%), corresponding to an annualized rate of 1.2/100 person-years. In all Cox regression analyses, the estimated adjusted GFR was an independent predictor of cardiovascular death. The equations which included cystatin C showed higher C-index compared to those which did not include cystatin C (0.75-0.76 vs. 0.71, respectively). The equations for the estimation of eGFR which include cystatin C are better associated with cardiovascular death compared to the race-free equations which include only creatinine. This finding adds on the related literature which supports the elimination of race in GFR-estimating equations, and promotion of the use of cystatin C.
    MeSH term(s) Humans ; Glomerular Filtration Rate ; Cystatin C/blood ; Male ; Female ; Aged ; Creatinine/blood ; Middle Aged ; Cardiovascular Diseases/mortality ; Proportional Hazards Models ; Biomarkers/blood
    Chemical Substances Cystatin C ; Creatinine (AYI8EX34EU) ; Biomarkers
    Language English
    Publishing date 2024-02-13
    Publishing country Italy
    Document type Journal Article
    ZDB-ID 2454173-4
    ISSN 1970-9366 ; 1828-0447
    ISSN (online) 1970-9366
    ISSN 1828-0447
    DOI 10.1007/s11739-023-03529-9
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  3. Article: A Simple-to-Use R Package for Mimicking Study Data by Simulations

    Koliopanos, Giorgos / Ojeda, Francisco / Ziegler, Andreas

    Methods of Information in Medicine

    2023  Volume 62, Issue 03/04, Page(s) 119–129

    Abstract: Background: Data protection policies might prohibit the transfer of existing study data to interested research groups. To overcome legal restrictions, simulated data can be transferred that mimic the structure but are different from the existing study ... ...

    Abstract Background: Data protection policies might prohibit the transfer of existing study data to interested research groups. To overcome legal restrictions, simulated data can be transferred that mimic the structure but are different from the existing study data.
    Objectives: The aim of this work is to introduce the simple-to-use R package Mock Data Generation (modgo) that may be used for simulating data from existing study data for continuous, ordinal categorical, and dichotomous variables.
    Methods: The core is to combine rank inverse normal transformation with the calculation of a correlation matrix for all variables. Data can then be simulated from a multivariate normal and transferred back to the original scale of the variables. Unique features of modgo are that it allows to change the correlation between variables, to perform perturbation analysis, to handle multicenter data, and to change inclusion/exclusion criteria by selecting specific values of one or a set of variables. Simulation studies on real data demonstrate the validity and flexibility of modgo.
    Results: modgo mimicked the structure of the original study data. Results of modgo were similar with those from two other existing packages in standard simulation scenarios. modgo's flexibility was demonstrated on several expansions.
    Conclusion: The R package modgo is useful when existing study data may not be shared. Its perturbation expansion permits to simulate truly anonymized subjects. The expansion to multicenter studies can be used for validating prediction models. Additional expansions can support the unraveling of associations even in large study data and can be useful in power calculations.
    Keywords data privacy ; perturbation analysis ; statistical disclosure control ; synthetic data ; validation study
    Language English
    Publishing date 2023-03-07
    Publisher Georg Thieme Verlag KG
    Publishing place Stuttgart ; New York
    Document type Article
    ZDB-ID 3500-2
    ISSN 2511-705X ; 0026-1270
    ISSN (online) 2511-705X
    ISSN 0026-1270
    DOI 10.1055/a-2048-7692
    Database Thieme publisher's database

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  4. Article ; Online: Transcatheter Aortic Valve Implantation in a Patient With Degenerated Aortic Homograft and Anomalous Right Coronary Artery Originating From Left Aortic Sinus.

    Muñoz-Rodríguez, Rebeca / Bosa-Ojeda, Francisco / Yanes-Bowden, Geoffrey / Lacalzada-Almeida, Juan

    CASE (Philadelphia, Pa.)

    2023  Volume 7, Issue 10, Page(s) 405–408

    Language English
    Publishing date 2023-05-17
    Publishing country United States
    Document type Case Reports
    ISSN 2468-6441
    ISSN (online) 2468-6441
    DOI 10.1016/j.case.2023.04.002
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: SCORE2 models allow consideration of sex-specific cardiovascular disease risks by region.

    Hageman, Steven / Pennells, Lisa / Ojeda, Francisco / Kaptoge, Stephen / Dorresteijn, Jannick / Di Angelantonio, Emanuele

    European heart journal

    2022  Volume 43, Issue 3, Page(s) 241–242

    MeSH term(s) Cardiovascular Diseases/epidemiology ; Female ; Humans ; Male ; Tomography, Optical Coherence
    Language English
    Publishing date 2022-01-25
    Publishing country England
    Document type Journal Article ; Comment
    ZDB-ID 603098-1
    ISSN 1522-9645 ; 0195-668X
    ISSN (online) 1522-9645
    ISSN 0195-668X
    DOI 10.1093/eurheartj/ehab761
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  6. Article ; Online: Calibrating machine learning approaches for probability estimation: A comprehensive comparison.

    Ojeda, Francisco M / Jansen, Max L / Thiéry, Alexandre / Blankenberg, Stefan / Weimar, Christian / Schmid, Matthias / Ziegler, Andreas

    Statistics in medicine

    2023  Volume 42, Issue 29, Page(s) 5451–5478

    Abstract: Statistical prediction models have gained popularity in applied research. One challenge is the transfer of the prediction model to a different population which may be structurally different from the model for which it has been developed. An adaptation to ...

    Abstract Statistical prediction models have gained popularity in applied research. One challenge is the transfer of the prediction model to a different population which may be structurally different from the model for which it has been developed. An adaptation to the new population can be achieved by calibrating the model to the characteristics of the target population, for which numerous calibration techniques exist. In view of this diversity, we performed a systematic evaluation of various popular calibration approaches used by the statistical and the machine learning communities for estimating two-class probabilities. In this work, we first provide a review of the literature and, second, present the results of a comprehensive simulation study. The calibration approaches are compared with respect to their empirical properties and relationships, their ability to generalize precise probability estimates to external populations and their availability in terms of easy-to-use software implementations. Third, we provide code from real data analysis allowing its application by researchers. Logistic calibration and beta calibration, which estimate an intercept plus one and two slope parameters, respectively, consistently showed the best results in the simulation studies. Calibration on logit transformed probability estimates generally outperformed calibration methods on nontransformed estimates. In case of structural differences between training and validation data, re-estimation of the entire prediction model should be outweighted against sample size of the validation data. We recommend regression-based calibration approaches using transformed probability estimates, where at least one slope is estimated in addition to an intercept for updating probability estimates in validation studies.
    MeSH term(s) Humans ; Logistic Models ; Machine Learning ; Models, Statistical ; Software ; Probability
    Language English
    Publishing date 2023-10-17
    Publishing country England
    Document type Review ; Journal Article
    ZDB-ID 843037-8
    ISSN 1097-0258 ; 0277-6715
    ISSN (online) 1097-0258
    ISSN 0277-6715
    DOI 10.1002/sim.9921
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  7. Article ; Online: Caracterización epidemiológica de infección por SARS-CoV-2 del personal de salud de un hospital universitario en Santiago de Chile.

    Saint-Pierre-Contreras, Gustavo / Silva-Ojeda, Francisco / Conei-Valencia, Daniel / Cifuentes-Díaz, Marcela

    Revista chilena de infectologia : organo oficial de la Sociedad Chilena de Infectologia

    2021  Volume 38, Issue 2, Page(s) 144–151

    Abstract: Background: The SARS-CoV-2 outbreak originated in the Hubei province in China spread rapidly throughout the world during the first months of 2020. On March 3, the first case was reported in Chile; at 17 days the first case of COVID-19 healthcare worker ( ...

    Title translation Epidemiological characterization of infection by SARS-CoV-2 of the healthcare workers of a university hospital in Santiago de Chile.
    Abstract Background: The SARS-CoV-2 outbreak originated in the Hubei province in China spread rapidly throughout the world during the first months of 2020. On March 3, the first case was reported in Chile; at 17 days the first case of COVID-19 healthcare worker (HCW) was notified in our institution.
    Aim: To describe the demographic characteristics and the incidence of SARS-CoV-2 infection in the HCW of a university hospital in Chile.
    Material and method: Retrospective study of SARS-CoV-2 infection on HCW in a university hospital between March 1 and May 31, 2020.
    Results: There were 273 positive cases. In the period under study, we had an incidence of 5.8%. When we separated the cases into clinical and non-clinical personnel, it was observed that their incidences were practically identical (5.8 vs. 5.7% p = 0.9430). 88% of the officials were oligosymptomatic or asymptomatic at the beginning of the clinical presentation and only 12% had a fever before the medical consultation.
    Conclusion: The incidence reported in the study was around 5 times that reported in Wuhan. If we apply the current definition of cases, we would lose 4 out of 5 cases. 88% of HPW did not present criteria to be considered suspicious, so it would be advisable in HCW to eliminate fever as a criterion to improve the research and trace their contacts on time.
    MeSH term(s) COVID-19 ; Chile/epidemiology ; Health Personnel ; Hospitals, University ; Humans ; Retrospective Studies ; SARS-CoV-2
    Language Spanish
    Publishing date 2021-06-28
    Publishing country Chile
    Document type Journal Article
    ZDB-ID 2048815-4
    ISSN 0717-6341 ; 0716-1018
    ISSN (online) 0717-6341
    ISSN 0716-1018
    DOI 10.4067/S0716-10182021000200144
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Retraso de crecimiento y desarrollo puberal en el síndrome de Gitelman.

    García García, Emilio / Jiménez Moreno, Marta / de la Cerda Ojeda, Francisco

    Medicina clinica

    2021  Volume 157, Issue 12, Page(s) 588–589

    Title translation Delayed growth and puberty in Gitelman syndrome.
    MeSH term(s) Gitelman Syndrome/diagnosis ; Gitelman Syndrome/genetics ; Humans ; Hypokalemia ; Puberty
    Language Spanish
    Publishing date 2021-05-24
    Publishing country Spain
    Document type Case Reports
    ZDB-ID 411607-0
    ISSN 1578-8989 ; 0025-7753
    ISSN (online) 1578-8989
    ISSN 0025-7753
    DOI 10.1016/j.medcli.2021.01.025
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  9. Article ; Online: Previous Catheter Ablation Predicts In-Hospital Restoration of Sinus Rhythm in Patients Presenting with Recent-Onset Atrial Fibrillation-The Retrospective HAMBURG-AF Study.

    Schulte-Steinberg, Benedict / Aydin, Muhammet Ali / Moser, Ana Theresa / Ojeda, Francisco / Karakas, Mahir

    Medicina (Kaunas, Lithuania)

    2021  Volume 57, Issue 8

    Abstract: Background and Objectives: ...

    Abstract Background and Objectives:
    MeSH term(s) Atrial Fibrillation/epidemiology ; Atrial Fibrillation/surgery ; Catheter Ablation ; Hospitals ; Humans ; Recurrence ; Retrospective Studies ; Treatment Outcome
    Language English
    Publishing date 2021-07-30
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2188113-3
    ISSN 1648-9144 ; 1010-660X
    ISSN (online) 1648-9144
    ISSN 1010-660X
    DOI 10.3390/medicina57080776
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Response by Magnussen et al to Letter Regarding Article, "Sex Differences and Similarities in Atrial Fibrillation Epidemiology, Risk Factors, and Mortality in Community Cohorts: Results From the BiomarCaRE Consortium (Biomarker for Cardiovascular Risk Assessment in Europe)".

    Magnussen, Christina / Ojeda, Francisco M / Schnabel, Renate B

    Circulation

    2018  Volume 137, Issue 19, Page(s) 2087–2088

    MeSH term(s) Atrial Fibrillation ; Biomarkers ; Cardiovascular Diseases ; Europe ; Female ; Humans ; Male ; Risk Assessment ; Risk Factors
    Chemical Substances Biomarkers
    Language English
    Publishing date 2018-04-18
    Publishing country United States
    Document type Letter ; Comment
    ZDB-ID 80099-5
    ISSN 1524-4539 ; 0009-7322 ; 0069-4193 ; 0065-8499
    ISSN (online) 1524-4539
    ISSN 0009-7322 ; 0069-4193 ; 0065-8499
    DOI 10.1161/CIRCULATIONAHA.118.033968
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