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7 Publications visible to you, out of a total of 7
The reliability of a restraint sensor system for the computer-supported detection of spinal stabilizing muscle deficiencies.
Genetical Statistics and Systems Biology

Abstract (Expand)

BACKGROUND: The presence of muscular deficiency seems to be a major cause of back pain that requires counteractions. Considering that the autochthonous back muscles, responsible for straightening and … stabilizing the spine, cannot be activated voluntarily, they can be strengthened only through specific training. The computer-supported test and training system (CTT) Centaur (BfMC GmbH, Leipzig, SN, Germany) seems well suited for this purpose. To show its potential as a reliable diagnostic and training tool, this study aimed to evaluate the test-retest reliability of this 3D spatial rotation device. METHODS: A prospective pilot study was conducted in 20 healthy volunteers of both sexes. For test-retest reliability analysis, three measurements were performed with a two-day interval between each measurement. Each measurement consisted of a one-minute endurance test performed in eight different positions (transverse plane). During the test, the subject was tilted by 90 degrees in the sagittal plane from a neutral, upright position. Meanwhile, the subject's level of upper body stabilization along the body axis was assessed. All trunk movements (momentum values) were quantified by a multicomponent force sensor and standardized relative to the subject's upper body mass. The range of motion was assessed by 95% confidence ellipse analysis. Here, all position-specific confidence ellipses for each measurement were merged to a summarized quantity. Finally, ICC analysis using a single-rating, absolute agreement, two-way mixed-effects model and a Bland-Altman plot was performed to determine the reliability. RESULTS: Considering all measurements (t1, t2, t3), the ICC for reliability evaluation was 0.805, and the corresponding 95% confidence interval (CI) was [0.643, 0.910]. Moreover, the Bland-Altman plots for all three pairs of time points did not show significant differences. CONCLUSION: This study concludes that the CTT Centaur shows good test-retest reliability, indicating it can be used in clinical practice in the future.

Authors: C. Pfeifle, M. Edel, S. Schleifenbaum, A. Kuhnapfel, C. E. Heyde

Date Published: 7th Sep 2020

Publication Type: Journal article

Genetic association study of eight steroid hormones and implications for sexual dimorphism of coronary artery disease
LIFE Adult, Genetical Statistics and Systems Biology, LIFE Heart

Abstract (Expand)

CONTEXT: Steroid hormones are important regulators of physiological processes in humans and are under genetic control. A link to coronary artery disease (CAD) is supposed. OBJECTIVE: Our main objective …e was to identify genetic loci influencing steroid hormone levels. As secondary aim, we searched for causal effects of steroid hormones on CAD. DESIGN: We conducted genome-wide meta-association studies for eight steroid hormones: cortisol, DHEA-S, estradiol and testosterone in two independent cohorts (LIFE-Adult, LIFE-Heart, max. n=7667), and progesterone, 17-hydroxyprogesterone, androstenedione and aldosterone in LIFE-Heart only (max. n=2070). All genome-wide significant loci were tested for sex interactions. Further, we tested if previously reported CAD SNPs were associated with our steroid hormone panel and investigated causal links between hormone levels and CAD status using Mendelian Randomization (MR) approaches. RESULTS: We discovered 15 novel associated loci for 17-hydroxyprogesterone, progesterone, DHEA-S, cortisol, androstenedione, and estradiol. Five of these loci relate to genes directly involved in steroid metabolism: CYP21A1, CYP11B1, CYP17A1, STS, and HSD17B12, almost completing the set of steroidogenic enzymes with genetic associations. Sexual dimorphisms were found for seven of the novel loci. Other loci correspond, e.g., to the WNT4/β-catenin pathway. MR revealed that cortisol, androstenedione, 17-hydroxyprogesterone and DHEA-S had causal effects on CAD. We also observed enrichment of cortisol and testosterone associations among known CAD hits. CONCLUSION: Our study greatly improves insight into genetic regulation of steroid hormones and their dependency on sex. These results could serve as a basis for analyzing sex-dimorphisms in other complex diseases.

Authors: J. Pott, YJ. Bae, K. Horn, A. Teren, Andreas Kühnapfel, H. Kirsten, U. Ceglarek, Markus Löffler, J. Thiery, J. Kratzsch, Markus Scholz

Date Published: 6th Jun 2019

Publication Type: Not specified

Human Diseases: coronary artery disease

Validity and reliability of three-dimensional scanning compared with conventional anthropometry for children and adolescents-response to the rebuttal by Sabour
Genetical Statistics and Systems Biology

Abstract

Pediatric Research accepted article preview online, 29 March 2017. doi:10.1038/pr.2017.76.

Authors: Fabian Glock, Markus Scholz, Andreas Kuehnapfel, Wieland Kiess

Date Published: 1st Aug 2017

Publication Type: Journal article

Validity and intraobserver reliability of three-dimensional scanning compared with conventional anthropometry for children and adolescents from a population-based cohort study
Genetical Statistics and Systems Biology

Abstract (Expand)

BACKGROUND Conventional anthropometric measurements are time consuming and require well trained medical staff. To use three-dimensional whole body laser scanning in daily clinical work, validity, and …d reliability have to be confirmed. METHODS We compared a whole body laser scanner with conventional anthropometry in a group of 473 children and adolescents from the Leipzig Research Centre for Civilization Diseases (LIFE-Child). Concordance correlation coefficients (CCC) were calculated separately for sex, weight, and age to assess validity. Overall CCC (OCCC) was used to analyze intraobserver reliability. RESULTS Body height and the circumferences of waist, hip, upper arm, and calf had an \textquotedblexcellent\textquotedbl (CCC ≥0.9); neck and thigh circumference, a \textquotedblgood\textquotedbl (CCC ≥0.7); and head circumference, a \textquotedbllow\textquotedbl (CCC \textless 0.5) degree of concordance over the complete study population. We observed dependencies of validity on sex, weight, and age. Intraobserver reliability of both techniques is \textquotedblexcellent\textquotedbl (OCCC ≥0.9). CONCLUSION Scanning is faster, requires less intensive staff training and provides more information. It can be used in an epidemiologic setting with children and adolescents but some measurements should be considered with caution due to reduced agreement with conventional anthropometry.

Authors: Fabian Glock, Mandy Vogel, Stephanie Naumann, Andreas Kuehnapfel, Markus Scholz, Andreas Hiemisch, Toralf Kirsten, Kristin Rieger, Antje Koerner, Markus Loeffler, Wieland Kiess

Date Published: 1st May 2017

Publication Type: Journal article

On the Conditional Power in Survival Time Analysis Considering Cure Fractions.
Genetical Statistics and Systems Biology

Abstract (Expand)

Conditional power of survival endpoints at interim analyses can support decisions on continuing a trial or stopping it for futility. When a cure fraction becomes apparent, conditional power cannot be … calculated accurately using simple survival models, e.g. the exponential model. Non-mixture models consider such cure fractions. In this paper, we derive conditional power functions for non-mixture models, namely the non-mixture exponential, the non-mixture Weibull, and the non-mixture Gamma models. Formulae were implemented in the R package CP. For an example data set of a clinical trial, we calculated conditional power under the non-mixture models and compared results with those under the simple exponential model.

Authors: A. Kuehnapfel, F. Schwarzenberger, M. Scholz

Date Published: 17th Mar 2017

Publication Type: Journal article

Body surface assessment with 3D laser-based anthropometry: reliability, validation, and improvement of empirical surface formulae.
Genetical Statistics and Systems Biology

Abstract (Expand)

PURPOSE Body surface area is a physiological quantity relevant for many medical applications. In clinical practice, it is determined by empirical formulae. 3D laser-based anthropometry provides an easy …y and effective way to measure body surface area but is not ubiquitously available. We used data from laser-based anthropometry from a population-based study to assess validity of published and commonly used empirical formulae. METHODS We performed a large population-based study on adults collecting classical anthropometric measurements and 3D body surface assessments (N = 1435). We determined reliability of the 3D body surface assessment and validity of 18 different empirical formulae proposed in the literature. The performance of these formulae is studied in subsets of sex and BMI. Finally, improvements of parameter settings of formulae and adjustments for sex and BMI were considered. RESULTS 3D body surface measurements show excellent intra- and inter-rater reliability of 0.998 (overall concordance correlation coefficient, OCCC was used as measure of agreement). Empirical formulae of Fujimoto and Watanabe, Shuter and Aslani and Sendroy and Cecchini performed best with excellent concordance with OCCC \textgreater 0.949 even in subgroups of sex and BMI. Re-parametrization of formulae and adjustment for sex and BMI slightly improved results. CONCLUSION In adults, 3D laser-based body surface assessment is a reliable alternative to estimation by empirical formulae. However, there are empirical formulae showing excellent results even in subgroups of sex and BMI with only little room for improvement.

Authors: Andreas Kuehnapfel, Peter Ahnert, Markus Loeffler, Markus Scholz

Date Published: 27th Jan 2017

Publication Type: Journal article

Reliability of 3D laser-based anthropometry and comparison with classical anthropometry
Genetical Statistics and Systems Biology

Abstract (Expand)

Anthropometric quantities are widely used in epidemiologic research as possible confounders, risk factors, or outcomes. 3D laser-based body scans (BS) allow evaluation of dozens of quantities in short … time with minimal physical contact between observers and probands. The aim of this study was to compare BS with classical manual anthropometric (CA) assessments with respect to feasibility, reliability, and validity. We performed a study on 108 individuals with multiple measurements of BS and CA to estimate intra- and inter-rater reliabilities for both. We suggested BS equivalents of CA measurements and determined validity of BS considering CA the gold standard. Throughout the study, the overall concordance correlation coefficient (OCCC) was chosen as indicator of agreement. BS was slightly more time consuming but better accepted than CA. For CA, OCCCs for intra- and inter-rater reliability were greater than 0.8 for all nine quantities studied. For BS, 9 of 154 quantities showed reliabilities below 0.7. BS proxies for CA measurements showed good agreement (minimum OCCC \textgreater 0.77) after offset correction. Thigh length showed higher reliability in BS while upper arm length showed higher reliability in CA. Except for these issues, reliabilities of CA measurements and their BS equivalents were comparable.

Authors: Andreas Kuehnapfel, Peter Ahnert, Markus Loeffler, Anja Broda, Markus Scholz

Date Published: 1st May 2016

Publication Type: Journal article

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