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251 Publications visible to you, out of a total of 251
The management of thyroid nodules: a retrospective analysis of health insurance data
Genetical Statistics and Systems Biology

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BACKGROUND\backslashr\backslashnIn Germany, about 59 000 thyroid operations are performed each year for uni- or multinodular goiter, most of them for diagnostic purposes. The rate of detection of thyroid … cancer in such operations is relatively low, at 1:15. Evidence suggests that the preoperative tests recommended in guidelines for estimating the risk of cancer are not being performed as often as they should. In the present study, we determined the measures that were actually taken to diagnose and treat thyroid nodules and compared the findings with the guideline recommendations.\backslashr\backslashnMETHOD\backslashr\backslashnWe retrospectively analyzed data from a single, large statutory healthinsurance carrier in Germany (AOK), determining the diagnostic and therapeutic measures that were reimbursed for 25 600 patients in whom a uni- or multinodular goiter was newly diagnosed in the second quarter of 2006 (none of these patients had carried such a diagnosis 1 year previously). We recorded the diagnostic measures performed in the preceding 9 months and all other tests and treatments, including surgery and radioactive iodine treatment, in the 2 years thereafter.\backslashr\backslashnRESULTS\backslashr\backslashnAmong patients who underwent surgery for uninodular goiter, the preoperative diagnostic studies included ultrasonography (in 100% of patients), scintigraphy (94%), measurement of thyroid-stimulating hormone (95%), measurement of calcitonin (9%), and fine-needle aspiration cytology (FNAC)(21%). An ultrasonographic examination was billed for only 28% of patients with uninodular goiter in the two years after the diagnosis was made. 13% of patients with uninodular goiter who were not operated on were given L-thyroxine, even though this is against guideline recommendations.\backslashr\backslashnCONCLUSION\backslashr\backslashnInadequate preoperative risk stratification of thyroid nodules may explain the large number of thyroid operations that are performed for diagnostic purposes, resulting in a low percentage of malignancies detected. Preoperative FNAC and calcitonin measurement should be used in the diagnostic evaluation of thyroid nodules far more often than this is now done. As a rule, follow-up ultrasonography should be performed for all thyroid nodules that are not operated on. Patients with non-operated thyroid nodules should not be given thyroxine. A limitation of this study is that diagnostic measures were only recorded if they were performed in the 9 months before surgery, with earlier diagnostic measures (if any) being missed.

Authors: Romy Wienhold, Markus Scholz, Jürgen-Bernhard Adler, Christian Günster, Ralf Paschke

Date Published: 2013

Publication Type: Journal article

Pharmacokinetic and -dynamic modelling of G-CSF derivatives in humans
Genetical Statistics and Systems Biology

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BACKGROUND\backslashr\backslashnThe human granulocyte colony-stimulating factor (G-CSF) is routinely applied to support recovery of granulopoiesis during the course of cytotoxic chemotherapies. However, … optimal use of the drug is largely unknown. We showed in the past that a biomathematical compartment model of human granulopoiesis can be used to make clinically relevant predictions regarding new, yet untested chemotherapy regimen. In the present paper, we aim to extend this model by a detailed pharmacokinetic and -dynamic modelling of two commonly used G-CSF derivatives Filgrastim and Pegfilgrastim.\backslashr\backslashnRESULTS\backslashr\backslashnModel equations are based on our physiological understanding of the drugs which are delayed absorption of G-CSF when applied to the subcutaneous tissue, dose-dependent bioavailability, unspecific first order elimination, specific elimination in dependence on granulocyte counts and reversible protein binding. Pharmacokinetic differences between Filgrastim and Pegfilgrastim were modelled as different parameter sets. Our former cell-kinetic model of granulopoiesis was essentially preserved, except for a few additional assumptions and simplifications. We assumed a delayed action of G-CSF on the bone marrow, a delayed action of chemotherapy and differences between Filgrastim and Pegfilgrastim with respect to stimulation potency of the bone marrow. Additionally, we incorporated a model of combined action of Pegfilgrastim and Filgrastim or endogenous G-CSF which interact via concurrent receptor binding. Unknown pharmacokinetic or cell-kinetic parameters were determined by fitting the predictions of the model to available datasets of G-CSF applications, chemotherapy applications or combinations of it. Data were either extracted from the literature or were received from cooperating clinical study groups. Model predictions fitted well to both, datasets used for parameter estimation and validation scenarios as well. A unique set of parameters was identified which is valid for all scenarios considered. Differences in pharmacokinetic parameter estimates between Filgrastim and Pegfilgrastim were biologically plausible throughout.\backslashr\backslashnCONCLUSION\backslashr\backslashnWe conclude that we established a comprehensive biomathematical model to explain the dynamics of granulopoiesis under chemotherapy and applications of two different G-CSF derivatives. We aim to apply the model to a large variety of chemotherapy regimen in the future in order to optimize corresponding G-CSF schedules or to individualize G-CSF treatment according to the granulotoxic risk of a patient.

Authors: Markus Scholz, Sibylle Schirm, Marcus Wetzler, Christoph Engel, Markus Loeffler

Date Published: 1st Dec 2012

Publication Type: Journal article

Impact of age on the efficacy of bone marrow mononuclear cell transplantation in experimental stroke
Genetical Statistics and Systems Biology

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Bone marrow-derived mononuclear cells (BM MNC) have been effectively used to treat experimental stroke. Most of the preclinical trials have been performed in young and healthy laboratory animals, even … though age and hypertension are major risk factors for stroke. To determine the influence of age on the properties of BM MNCs after cerebral ischemia, we compared the efficacy of aged and young BM MNC in an in vitro model of cerebral hypoxia and in an adapted in vivo model of stroke. Human BM MNCs were obtained from healthy young or aged donors and either co-cultured with rat hippocampal slices exposed to oxygen glucose deprivation (OGD), or transplanted intravenously 24 h after permanent middle cerebral artery occlusion in aged (18 months) spontaneously hypertensive rats (SHR). Efficacy was examined by quantification of hippocampal cell death, or respectively, by neurofunctional tests and MR investigations. Co-cultivation with young, but not with aged BM MNCs significantly reduced the hippocampal cell death after OGD. Transplantation of both young and old BM MNCs did not reduce functional deficits or ischemic lesion volume after stroke in aged SHR. These results suggest a significant impact of age on the therapeutic efficacy of BM MNCs after cerebral ischemia.

Authors: Daniel-Christoph Wagner, Mitja Bojko, Myriam Peters, Marlene Lorenz, Cornelia Voigt, Alexander Kaminski, Dirk Hasenclever, Markus Scholz, Alexander Kranz, Gesa Weise, Johannes Boltze

Date Published: 1st Dec 2012

Publication Type: Journal article

Automated photoplethysmography-based determination of ankle-brachial index: a validation study against Doppler sonography
Genetical Statistics and Systems Biology

Abstract (Expand)

INTRODUCTION\backslashr\backslashnDetermination of ankle-brachial-index (ABI) by manual Doppler is well established to screen for lower extremity arterial disease (LEAD) and to predict cardiovascular … risk. A new generation of digital-controlled devices promises automated ABI determination. The aim of this study was to determine comparability of automated photoplethysmography (PPG)-derived ABI calculation with the Doppler-ABI algorithm commonly used in cohort studies.\backslashr\backslashnMETHODS\backslashr\backslashnAutomated PPG-based ABI measurements [Vascular Explorer (VE) and Vicorder (VI)] were recorded from 112 limbs of healthy subjects and 22 limbs of patients with confirmed LEAD. Validity was evaluated on the basis of receiver-operating characteristic (ROC) analysis of clinical status and concordance with Doppler-ABI. Differences between cuff inflation [inf]- and deflation [def]-based method were studied in VE.\backslashr\backslashnRESULTS\backslashr\backslashnPPG-based ABI values were higher compared to Doppler-ABI (VI +0.06, VEinf +0.15, VEdef +0.09, p \textless 0.001, respectively). The difference was pronounced in pathological (\textless0.9), borderline (0.9-0.99) and low normal (1.0-1.09) ABI, but less in ABI \geq1.1. However, ROC analysis revealed excellent diagnostic value for LEAD (sensitivity/specificity) and comparable area under the curve at method-adapted ABI thresholds for all methods: Doppler (95/90 %, 0.95), VI (75/96 %, 0.91), VEinf (85/89 %, 0.93) and VEdef (80/98 %, 0.94).\backslashr\backslashnCONCLUSIONS\backslashr\backslashnDigital-controlled PPG-based ABI determination is a useful diagnostic application for LEAD. However, the systematic higher ABI in PPG-based measurement compared to Doppler and remarkable differences between the deflationary and inflationary method are critical for the interpretation of borderline and low normal ABI values where precise reading is essential to detect mild LEAD and subclinical disease and to predict cardiovascular risk. INTRODUCTION Determination of ankle-brachial-index (ABI) by manual Doppler is well established to screen for lower extremity arterial disease (LEAD) and to predict cardiovascular risk. A new generation of digital-controlled devices promises automated ABI determination. The aim of this study was to determine comparability of automated photoplethysmography (PPG)-derived ABI calculation with the Doppler-ABI algorithm commonly used in cohort studies. METHODS Automated PPG-based ABI measurements [Vascular Explorer (VE) and Vicorder (VI)] were recorded from 112 limbs of healthy subjects and 22 limbs of patients with confirmed LEAD. Validity was evaluated on the basis of receiver-operating characteristic (ROC) analysis of clinical status and concordance with Doppler-ABI. Differences between cuff inflation [inf]- and deflation [def]-based method were studied in VE. RESULTS PPG-based ABI values were higher compared to Doppler-ABI (VI +0.06, VEinf +0.15, VEdef +0.09, p \textless 0.001, respectively). The difference was pronounced in pathological (\textless0.9), borderline (0.9-0.99) and low normal (1.0-1.09) ABI, but less in ABI \geq1.1. However, ROC analysis revealed excellent diagnostic value for LEAD (sensitivity/specificity) and comparable area under the curve at method-adapted ABI thresholds for all methods: Doppler (95/90 %, 0.95), VI (75/96 %, 0.91), VEinf (85/89 %, 0.93) and VEdef (80/98 %, 0.94). CONCLUSIONS Digital-controlled PPG-based ABI determination is a useful diagnostic application for LEAD. However, the systematic higher ABI in PPG-based measurement compared to Doppler and remarkable differences between the deflationary and inflationary method are critical for the interpretation of borderline and low normal ABI values where precise reading is essential to detect mild LEAD and subclinical disease and to predict cardiovascular risk.

Authors: Frank Beutner, Andrej Teren, Stephan Gielen, Gerhard Schuler, Kerstin Wirkner, Daniel Tiller, Markus Loeffler, Markus Scholz

Date Published: 1st Nov 2012

Publication Type: Journal article

"Real-time-3-dimensional-full-volume"-datensatz: Nutzen in der problemfokussierten intraoperativen transösophagealen echokardiographie
Genetical Statistics and Systems Biology

Abstract (Expand)

BACKGROUND\backslashr\backslashnComprehensive intraoperative transesophageal echcardiography (TEE) includes various measurements for quantification of cardiac chambers and valves based on multiple two … dimensional (2D) standard views. Due to shortness of time during cardiac surgery most centres in Germany only carry out problem focussed intraoperative examinations which does not allow the complete repertoire of measurements to be exhausted. The aim of this study was to investigate which measurements for cardiac chamber and valve quantification can be performed with the acquisition of a real-time 3D full volume (RT-3D-FV) data set and to compare these measurements with those based on standard 2D views.\backslashr\backslashnMATERIALS AND METHODS\backslashr\backslashnIn patients undergoing elective surgical mitral valve repair a comprehensive 2D TEE examination according to the guidelines of the American Society of Echocardiography (ASE) and the Society of Cardiovascular Anesthesiologists (SCA) was performed after induction of anesthesia. Additionally, a RT-3D-FV TEE data set based on the midesophageal four chamber view was recorded (iE 33, Philips, Netherlands). All measurements of the 2D TEE and the RT-3D-FV dataset (Qlab) were performed offline by two independent examiners.\backslashr\backslashnRESULTS\backslashr\backslashnAfter approval by the local ethic committee and obtaining written informed consent 50 patients (31 male and 19 female) with a mean age of 59.4 \pm 11.5 years were enrolled in this study. All measurements recommended for chamber and valve quantification could be performed on the basis of the RT-3D-FV data set except for measurements of the sinus of Valsalva and the sinotubular junction. There was good correlation between the results of the two methods.\backslashr\backslashnCONCLUSIONS\backslashr\backslashnFor intraoperative problem focussed TEE examinations the acquisition of an additional RT-3D-FV TEE data set allows accurate measurement of most of the recommended chamber and valve quantification parameters.

Authors: A. Ender, S. Eibel, E. Hasheminejad, Markus Scholz, Udo X. Kaisers, Chirojit Mukherjee, Joerg Ender

Date Published: 1st Oct 2012

Publication Type: Journal article

A new evaluation and training system for micro-telemanipulation at the middle ear
Genetical Statistics and Systems Biology

Abstract (Expand)

In this article, a new surgical model for evaluating telemanipulators used in middle ear surgery is presented. The purpose of this work was to develop an evaluation and training system which imitates … a typical surgical task of middle ear surgery and which can easily be repeated in order to get significant result. The abstract task can be performed manually or by means of a microsurgical telemanipulator and guaranties stable experimental conditions between different subjects at any time. As a task the stapedotomy was chosen, due to the high demands in positioning and in applying forces to the delicate structures in the middle ear. The manual and telemanipulated performance of 15 ENT surgeons and 17 medical students was compared using this evaluation and training system. In this article, a new surgical model for evaluating telemanipulators used in middle ear surgery is presented. The purpose of this work was to develop an evaluation and training system which imitates a typical surgical task of middle ear surgery and which can easily be repeated in order to get significant result. The abstract task can be performed manually or by means of a microsurgical telemanipulator and guaranties stable experimental conditions between different subjects at any time. As a task the stapedotomy was chosen, due to the high demands in positioning and in applying forces to the delicate structures in the middle ear. The manual and telemanipulated performance of 15 ENT surgeons and 17 medical students was compared using this evaluation and training system.

Authors: Thomas Maier, Gero Strauss, Markus Scholz, Thomas Berger, Anne Kielhorn, Konrad Entsfellner, Christian Willim, Wolfgang Buscher, Andreas Dietz, Tim C. Lueth

Date Published: 1st Aug 2012

Publication Type: Journal article

KMWin--a convenient tool for graphical presentation of results from Kaplan-Meier survival time analysis.
GLA - German Lymphoma Alliance, Genetical Statistics and Systems Biology

Abstract (Expand)

BACKGROUND: Analysis of clinical studies often necessitates multiple graphical representations of the results. Many professional software packages are available for this purpose. Most packages are … either only commercially available or hard to use especially if one aims to generate or customize a huge number of similar graphical outputs. We developed a new, freely available software tool called KMWin (Kaplan-Meier for Windows) facilitating Kaplan-Meier survival time analysis. KMWin is based on the statistical software environment R and provides an easy to use graphical interface. Survival time data can be supplied as SPSS (sav), SAS export (xpt) or text file (dat), which is also a common export format of other applications such as Excel. Figures can directly be exported in any graphical file format supported by R. RESULTS: On the basis of a working example, we demonstrate how to use KMWin and present its main functions. We show how to control the interface, customize the graphical output, and analyse survival time data. A number of comparisons are performed between KMWin and SPSS regarding graphical output, statistical output, data management and development. Although the general functionality of SPSS is larger, KMWin comprises a number of features useful for survival time analysis in clinical trials and other applications. These are for example number of cases and number of cases under risk within the figure or provision of a queue system for repetitive analyses of updated data sets. Moreover, major adjustments of graphical settings can be performed easily on a single window. CONCLUSIONS: We conclude that our tool is well suited and convenient for repetitive analyses of survival time data. It can be used by non-statisticians and provides often used functions as well as functions which are not supplied by standard software packages. The software is routinely applied in several clinical study groups.

Authors: A. Gross, M. Ziepert, M. Scholz

Date Published: 23rd Jun 2012

Publication Type: Not specified

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