O Gefeller

Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Bavaria, Germany

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Publications (227)729.93 Total impact

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    ABSTRACT: Background Cobalt contact sensitization in consecutively tested patients is common. The sources of exposure, and thus clinical relevance, are mostly unclear.Objective To examine (i) long-term time trends of sensitization, (ii) risk factors that may point to relevant exposures, and (iii) coupling with nickel sensitization.Methods Data of all patients patch tested with cobalt(II) chloride hexahydrate (1% pet.) between 1992 and 2012 (n = 185 050) in the Information Network of Departments of Dermatology (IVDK, www.ivkd.org) were subjected to descriptive stratified and Poisson regression analysis.ResultsThe overall prevalence of positive patch test reactions was 5.23% (95% confidence interal 5.13–5.33%). Regarding time trends, there were significant increases for males aged 18–44 years and for females aged ≥45 years, and a significant variation of co-reactivity with nickel over time. Female sex almost doubled the risk of sensitization; age ≥45 years was associated with a 30% decrease in the risk of positive patch test reactions to cobalt, and atopic eczema with an approximately 20% increase.Conclusions Notwithstanding some diagnostic difficulties with the test preparation, a persistent, notable proportion of cobalt sensitization, isolated or coupled with nickel allergy, can be observed. This warrants further in-depth research into causative exposures, both at the workplace and in consumers.
    Contact Dermatitis 09/2014; · 2.93 Impact Factor
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    ABSTRACT: A high number of melanocytic naevi is one of the major risk factors for cutaneous melanoma. Therefore, counting the number of acquired naevi could be a useful strategy to identify individuals at an increased risk for targeted skin cancer screening. The aim of this study was to assess agreement between naevus self-counts and counts of trained examiners as well as to analyse potential determinants of the magnitude of agreement. In a large cross-sectional survey (n=1772), university students counted their naevi on both arms and were additionally examined by specifically trained examiners in a mutually blinded manner. Further data on other melanoma risk factors such as skin phototype, hair colour or freckling were collected by a questionnaire. The relative difference between the two naevus counts and the ratio of the counts were calculated to quantify agreement. Regression modelling was performed to identify independent determinants of agreement. The overall agreement was moderate, with participants counting on average 14% more naevi than the examiners. In terms of the potential determinants associated with agreement, skin type and medical education showed a strong effect. The difference in naevus counts was significantly larger for individuals with lighter skin types compared with those with a dark skin (Fitzpatrick type IV), and medical students yielded a naevus count more similar to the examiner's count than nonmedical students. Naevus self-counts can only provide a rough estimate of the number of naevi, but may not be accurate enough to reliably identify a high-risk group for melanoma screening, especially in individuals with light skin types.
    Melanoma Research 07/2014; · 2.52 Impact Factor
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    ABSTRACT: Boosting algorithms to simultaneously estimate and select predictor effects in statistical models have gained substantial interest during the last decade. This review article aims to highlight recent methodological developments regarding boosting algorithms for statistical modelling especially focusing on topics relevant for biomedical research. We suggest a unified framework for gradient boosting and likelihood-based boosting (statistical boosting) which have been addressed strictly separated in the literature up to now. Statistical boosting algorithms have been adapted to carry out unbiased variable selection and automated model choice during the fitting process and can nowadays be applied in almost any possible type of regression setting in combination with a large amount of different types of predictor effects. The methodological developments on statistical boosting during the last ten years can be grouped into three different lines of research: (i) efforts to ensure variable selection leading to sparser models, (ii) developments regarding different types of predictor effects and their selection (model choice), (iii) approaches to extend the statistical boosting framework to new regression settings.
    Methods of information in medicine. 03/2014; 53(5).
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    ABSTRACT: The concept of boosting emerged from the field of machine learning. The basic idea is to boost the accuracy of a weak classifying tool by combining various instances into a more accurate prediction. This general concept was later adapted to the field of statistical modelling. This review article attempts to highlight this evolution of boosting algorithms from machine learning to statistical modelling. We describe the AdaBoost algorithm for classification as well as the two most prominent statistical boosting approaches, gradient boosting and likelihood-based boosting. Although both appraoches are typically treated separately in the literature, they share the same methodological roots and follow the same fundamental concepts. Compared to the initial machine learning algorithms, which must be seen as black-box prediction schemes, statistical boosting result in statistical models which offer a straight-forward interpretation. We highlight the methodological background and present the most common software implementations.
    Methods of information in medicine. 03/2014; 53(5).
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    ABSTRACT: Background Cosmetics for bleaching, waving/relaxing and dyeing hair contain well-known allergens, leading to a substantial number of cases of allergic contact dermatitis.Objective To compare the frequency of important contact allergens (i) between two distinct groups of exposed patients, and (ii) with previous surveillance data.Methods On the basis of data collected by the Information Network of Departments of Dermatology (IVDK; www.ivkd.org) between 2007 and 2012 in 824 female hairdressers and 2067 female clients, the current spectrum of contact sensitization to ingredients of hair cosmetics, as contained in different pertinent series, is described.ResultsA similar burden of sensitization as in previous analyses was observed, but with some increase in sensitization to oxidative hair dye components in clients. Some allergens mainly affected hairdressers, such as ammonium persulfate (18.7% positive) and glyceryl monothioglycolate (GMTG; still 4.7% positive, with a few cases also in young hairdressers, despite removal from the German market).Conclusions Hair dyes remain important contact allergens, despite various attempts by the cosmetic industry to introduce hair dyes with lower allergenic potential. The re-emergence of GMTG as an occupational allergen should be considered as a warning signal (‘sentinel event’) prompting close monitoring.
    Contact Dermatitis 03/2014; · 2.93 Impact Factor
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    ABSTRACT: Public health campaigns have improved knowledge on UVR-associated skin cancer risk and increased sun protection awareness. However, tanned skin is still a common beauty ideal. The relationship between knowledge, attitudes and protective behavior is not fully understood yet. A population-based survey was thus performed in the district of Erlangen involving 2,619 parents of 3- to 6-year old children. By means of a self-administered standardized questionnaire parental knowledge about risk factors for skin cancer, their attitudes towards tanning and details of protective measures taken for their children were assessed. The study analyzed specifically the impact of parental tanning attitudes on sun-protective measures for their children while controlling for parental knowledge about skin cancer risk factors. While parental knowledge was significantly (inversely) associated with agreement to the statement "Tanned skin is healthy skin", this was not the case for "Tanning makes me look better". Overall, tanning affirmative attitudes were inversely associated with protective measures taken for the children, whereas parental knowledge had a positive impact on sun protection at the beach only. Multivariable analyses provided evidence for an effect of parental attitude on protective behavior independent of parental knowledge. Tanning attitudes and tanned skin as the misguided ideal of beauty need to be addressed in future public health campaigns to enhance the effectiveness of preventive activities in changing sun protective behavior.
    International Journal of Environmental Research and Public Health 01/2014; 11(5):4768-81. · 2.00 Impact Factor
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    ABSTRACT: Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC) is a synthetic fragrance chemical and an important contact allergen, at least in Europe. Despite this importance, little is known about risk factors associated with this allergen. To examine factors from the history and clinical presentation of patch tested patients associated with HICC sensitization. Contact allergy surveillance data of 95 637 patients collected by the Information Network of Departments of Dermatology (IVDK, www.ivkd.org) in 2002-2011 were analysed. Point and interval estimates of the relative risk were derived from multifactorial logistic regression modelling. The overall prevalence of HICC sensitization was 2.24%. The strongest risk factors were polysensitization and dermatitis of the axillae, followed by dermatitis at other sites. No consistent and significant time trend was observed in this analysis. As compared with the youngest patients, the odds of HICC sensitization increased approximately three-fold in the 52-67-year age group, and strongly declined with further increasing age. The risk pattern with regard to age and affected anatomical site differed from that observed with other fragrance screening allergens. Cosmetic exposure, as broadly defined here, was a stronger and more prevalent individual risk factor than occupational exposure.
    Contact Dermatitis 08/2013; 69(2):72-7. · 2.93 Impact Factor
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    ABSTRACT: No observed event is a special, but not uncommon, result in patch test studies. The interpretation of such findings depends critically on the sample size (n) of the investigation, and is statistically addressed by the use of confidence intervals (CIs). To define the statistically correct method of calculating a CI with a confidence level of 1 - α, where α denotes the tolerated statistical error probability, for an observed prevalence of 0%. A literature survey and evaluation of the statistical methods was conducted. The popular statistical software packages spss™ and sas™ were examined with regard to the methods implemented, and the results obtained, for estimating such CIs in this special case. The evaluation identified [0; 1 - α(1/n) ], which is well approximated by [0; 3/n] for α = 0.05, as an appropriate method to compute a CI with a confidence level of 1 - α. The resulting CI is an exact one, and more efficient than standard solutions. Popular statistical software such as spss™ and sas™ offers only various inefficient or even invalid procedures, but does not include this method. It is easy to calculate a CI for an observed prevalence of 0% obtained in some studies. Such a CI facilitates the interpretation of such a finding, as it puts the observed zero result into adequate statistical perspective.
    Contact Dermatitis 07/2013; · 2.93 Impact Factor
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    J Schwitulla, O Gefeller, A Schnuch, W Uter
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    ABSTRACT: BACKGROUND: "Polysensitisation" (PS) is usually defined as contact sensitisation to 3 or more unrelated haptens of the baseline patch test series. Despite PS being an important clinical phenotype indicating increased susceptibility to contact allergy, statistical approaches to analyse PS have hitherto been preliminary. OBJECTIVES: To apply an appropriate regression model for count data, namely, negative binomial hurdle regression, to a large set of clinical patch test data with the aim of estimating PS risk in more detail than previously achieved. METHODS: The detailed information provided by the hurdle model includes a separate estimation of an 'increment factor' quantifying the likelihood of further positive reactions, i.e. PS. Clinical data of 126878 patients patch tested by departments comprising the IVDK network (www.ivdk.org) between 1995 and 2010 were included. RESULTS: Regarding anatomical sites as exposure (surrogate), the axillae and the feet were found to be strong PS risk factors. Moreover, age was a strong PS risk factor, and less so, female sex. In comparison, atopic eczema and occupational dermatitis were less important risk factors. Single allergens contributed to PS to a varying extent. CONCLUSION: The data presented point to some, very likely exposure-related, risk factors which need to be considered in future PS research, e.g., addressing the genetic basis for PS. This article is protected by copyright. All rights reserved.
    British Journal of Dermatology 05/2013; · 3.76 Impact Factor
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    ABSTRACT: Ultraviolet radiation is an established skin carcinogen. By analysing the seasonality of melanoma diagnoses, the effect of this risk factor can be examined indirectly. However, previous studies yielded conflicting results, because of vastly differing analytical methods and diverse study designs. Therefore, to validate the findings by Chaillol and colleagues based on 3868 melanoma diagnoses from Northern Ireland, we used an identical methodology to examine the seasonal effects on monthly incidences of 11 901 cutaneous malignant melanoma cases registered from 2003 until 2008 in Bavaria, Germany. Multivariable regression models for count data were used to estimate the effect of seasons while taking into account sex, age, year of diagnosis, Breslow thickness and anatomical site. Point and interval estimates of the adjusted relative risks associated with seasons were compared with the findings of the Irish study. Both analyses demonstrated a promoting effect of intermittent ultraviolet radiation on cutaneous melanoma of a thickness of 2 mm or less evolving on the extremities, whereas no seasonality for melanomas on the trunk was evident. Differences were identified with regard to thick melanomas. In the present analysis, only melanomas with a Breslow thickness of more than 2 mm were also found to be associated with season, in particular, the melanomas on the limbs. Hence, in contrast to the data of, and to the interpretation by, Chaillol and colleagues, an effect of ultraviolet radiation on melanoma progression from thin to thick cannot be excluded.
    Melanoma research 04/2013; · 2.06 Impact Factor
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    ABSTRACT: Aim: The Material Values Scale is an instrument to assess beliefs about the importance to own material things. This instrument originally consists of the three subscales: 'centrality', 'success', and 'happiness'. The present study investigated the psychometric properties of the German version of the MVS (G-MVS). Method: A population-based sample of 2,295 adult Germans completed the questionnaire in order to investigate the factorial structure. To test construct validity, additional samples were gathered among patients with compulsive buying (N=52) and medical students (N=347) who also answered the Compulsive Buying Scale (CBS) and the Patient Health Questionnaire depression scale (PHQ-8). Results: In the German population-based sample we could not confirm the 3-factor model but rather suggest a 2-factor solution with a first collapsed factor 'centrality/success', and the second factor 'happiness'. Patients with compulsive buying showed the highest scores on the G-MVS. While G-MVS scores among compulsive buyers and medical students were significantly related to compulsive buying scores, the correlation between the G-MVS and the depression measure appeared substantially lower. We did not find any gender differences regarding materialism, neither in the population-based sample nor in the students' or compulsive buyers' samples. However, age was negatively related to G-MVS scores. Conclusion: Confirmatory factor analyses suggest a 2-factor model of the G-MVS. Overall, the results indicate the use of the G-MVS as a brief, psychometrically sound, and potentially valid measure for the assessment of material values.
    Psycho-social medicine. 01/2013; 10:Doc05.
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    ABSTRACT: This study evaluated the psychometric properties of the German version of the 21-item Exercise Dependence Scale (EDS-G), which was administered in a large representative German sample (N = 1,611). In order to examine convergent validity, we also asked participants to answer the Eating Disorder Examination-Questionnaire (EDE-Q). To investigate the discriminant validity, clients of fitness centers (N = 129), sport students (N = 85), and medical students (N = 129) filled out the EDS-G. In this German population-based sample, the seven-factor structure suggested by the original authors as well as a higher-order model (7 + 1 factor model) were supported. The total EDS-G scale showed an excellent internal reliability and was positively related to the EDE-Q total and subscale scores. The EDS-G scores differentiated between samples with varying degrees of exercise. In summary, the results indicate that the EDS-G is a psychometrically sound and potentially valid brief measure for the assessment of exercise dependence symptoms. (PsycINFO Database Record (c) 2013 APA, all rights reserved)
    European Journal of Psychological Assessment 01/2013; 29(3):213. · 2.53 Impact Factor
  • W Uter, M Benz, A Mayr, O Gefeller, A Pfahlberg
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    ABSTRACT: BACKGROUND/PURPOSE: Different devices are used for the non-invasive measurement of (constitutive) skin pigmentation in (epidemiological) studies. Reproducibility of measurements with the Chromameter (CM, model CR 300, Minolta, Osaka) and the Reflectometer (RM, Courage & Khazaka, Cologne) has not yet been examined in detail and was addressed in a set of four experiments and studies respectively. METHODS: Regarding the CM, the Y value of the Yxy CIE 1931 colour system was utilized, representing lightness in this colour space, while the RM measured reflectance at 660 nm with a small bandwidth of 20 nm. Both devices measure reflectance on a scale from 0 to 100%, however, in different wavelength ranges. Between 3 and 20 repetitions were performed on standard grey scales and different sets of human volunteers, including RM measurements in a large epidemiological field study. RESULTS: While the coefficient of variation (V) increases and the intraclass correlation coefficient decreases from controlled laboratory to field conditions, reproducibility remained in a range considered acceptable, if adequate study conditions were maintained. In a direct comparison on human skin, V of the RM was significantly smaller than that of the CM. CONCLUSION: Both devices can be used confidently in field studies; however, based on considerations of skin optics and in view of slightly lesser variability, the RM may be preferable.
    Skin Research and Technology 12/2012; · 1.41 Impact Factor
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    ABSTRACT: BACKGROUND: Binge eating disorder (BED) is a prevalent clinical eating disorder associated with increased psychopathology, psychiatric comorbidity, overweight and obesity, and increased health care costs. Since its inclusion in the DSM-IV, a few randomized controlled trials (RCTs) have suggested efficacy of book-based self-help interventions in the treatment of this disorder. However, evidence from larger RCTs is needed. Delivery of self-help through new technologies such as the internet should be investigated in particular, as these approaches have the potential to be more interactive and thus more attractive to patients than book-based approaches. This study will evaluate the efficacy of an internet-based guided self-help program (GSH-I) and cognitive-behavioral therapy (CBT), which has been proven in several studies to be the gold standard treatment for BED, in a prospective multicenter randomized trial. METHODS: The study assumes the noninferiority of GSH-I compared to CBT. Both treatments lasted 4 months, and maintenance of outcome will be assessed 6 and 18 months after the end of treatment. A total of 175 patients with BED and a body mass index between 27 and 40 kg/m2 were randomized at 7 centers in Germany and Switzerland. A 20% attrition rate was assumed. As in most BED treatment trials, the difference in the number of binge eating days over the past 28 days is the primary outcome variable. Secondary outcome measures include the specific eating disorder psychopathology, general psychopathology, body weight, quality of life, and self-esteem. Predictors and moderators of treatment outcome will be determined, and the cost-effectiveness of both treatment conditions will be evaluated. RESULTS: The methodology for the INTERBED study has been detailed. CONCLUSIONS: Although there is evidence that CBT is the first-line treatment for BED, it is not widely available. As BED is still a recent diagnostic category, many cases likely remain undiagnosed, and a large number of patients either receive delayed treatment or never get adequate treatment. A multicenter efficacy trial will give insight into the efficacy of a new internet-based guided self-help program and will allow a direct comparison to the evidence-based gold standard treatment of CBT in Germany.Trial RegistrationCurrent Controlled Trials ISRCTN40484777German Clinical Trial Register DRKS00000409.
    Trials 11/2012; 13(1):220. · 2.21 Impact Factor
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    ABSTRACT: To assess and to evaluate possible effects arising from Web-based data collection on the results of a study. We analyzed participants of the German Weight Control Registry (GWCR) of whom 328 chose to use Web-based questionnaires and 139 preferred to participate via a traditional postal survey. Furthermore, we included data of 212 individuals sampled independently from the general population who fulfilled the study's inclusion criteria-giving us the chance to differentiate between response bias (concerning Web-based data collection) and general selection bias (concerning participation in the GWCR). In addition to selection bias (GWCR participants are overall better educated, more likely to live in a partnership, more often female, and older than the general population), we also found a substantial response bias: Participants using the Internet were younger, better educated, and more often male compared with participants preferring the paper-and-pencil version. However, after adjusting for these differences, we found no additional direct effect of Web-based data collection on any of the outcome variables. Web-based epidemiologic studies still do not attract the same participants as postal surveys, even in highly industrialized countries. However, after adjusting for this bias, the same results can be expected.
    Journal of clinical epidemiology 06/2012; 65(9):970-7. · 5.48 Impact Factor
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    ABSTRACT: Erythropoietin (EPO) improves cognitive performance in clinical studies and rodent experiments. We hypothesized that an intrinsic role of EPO for cognition exists, with particular relevance in situations of cognitive decline, which is reflected by associations of EPO and EPO receptor (EPOR) genotypes with cognitive functions. To prove this hypothesis, schizophrenic patients (N > 1000) were genotyped for 5' upstream-located gene variants, EPO SNP rs1617640 (T/G) and EPORSTR(GA)(n). Associations of these variants were obtained for cognitive processing speed, fine motor skills and short-term memory readouts, with one particular combination of genotypes superior to all others (p < 0.0001). In an independent healthy control sample (N > 800), these associations were confirmed. A matching preclinical study with mice demonstrated cognitive processing speed and memory enhanced upon transgenic expression of constitutively active EPOR in pyramidal neurons of cortex and hippocampus. We thus predicted that the human genotypes associated with better cognition would reflect gain-of-function effects. Indeed, reporter gene assays and quantitative transcriptional analysis of peripheral blood mononuclear cells showed genotype-dependent EPO/EPOR expression differences. Together, these findings reveal a role of endogenous EPO/EPOR for cognition, at least in schizophrenic patients.
    Molecular Medicine 06/2012; 18(9):1029-40. · 4.47 Impact Factor
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    ABSTRACT: The preservative methylchloroisothiazolinone (MCI)/methylisothiazo- linone (MI) is an important allergen, and has thus been subject to regulation in some areas of exposure, mainly in cosmetics. To examine whether a decline in sensitization prevalence and intensity of elicitation (by the patch test) can be observed, either overall, or in certain subgroups defined by causative exposures. On the basis of long-term contact allergy surveillance data collected by the Information Network of Departments of Dermatology (www.ivkd.org), 1992-2010, in the course of 171 883 consultations, the time trend of (different grades of) positive patch test reactions to MCI/MI (0.01% aqua) was examined in an age-stratified analysis. The overall frequency of positive patch test reactions was 2.33% (95% confidence interval 2.26-2.4%). No significant overall trend of positive reactions or of the distribution of +, ++ and + + + reactions (p > 0.05) was observed, similarly to what was found for patients in whom cosmetics were recorded as causative exposure (p = 0.55). In contrast, in patients with occupational contact dermatitis who were < 40 years of age, a significant increase in prevalence, by 0.87 percentage points per decade, was identified (p = 0.018). Both applications of MCI/MI, cosmetic and industrial, should be the target of further preventive efforts.
    Contact Dermatitis 05/2012; 67(3):125-9. · 2.93 Impact Factor
  • M Schmid, O Gefeller, T Hothorn
    Methods of Information in Medicine 03/2012; 51(2):150-1. · 1.08 Impact Factor
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    J Li, W Uter, A Pfahlberg, O Gefeller
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    ABSTRACT: Reducing exposure to ultraviolet (UV) radiation is the main effective measure for preventing skin cancer. Educational campaigns targeting sun protection have been focused either on behaviour on the beach during the summer holiday alone, or during everyday outdoor activities of the children. Little is known about the comparison between these different settings. To analyse whether parents apply similar protective measures to reduce UV exposure for their young children in different outdoor environments. Families (n = 2619) with children aged 3-6 years (response: 64·7%) were enrolled in a population-based survey in the German city of Erlangen and its surrounding rural county. Using a self-administered standardized questionnaire parents gave information about demographic and photosensitivity data of their children, their knowledge about risk factors for skin cancer and their typical instructions given to their children when these played outside on a summer day in different outdoor environments. Significant discrepancies regarding the four UV protective measures (clothes, shade, sunhat, sunscreen) for children between an everyday outdoor setting and a holiday setting on the beach were observed. A high level of parental risk factor knowledge was significantly associated with a better protection for children in all four measures only on the beach. Photosensitivity and demographic characteristics had some impact on protective behaviour, too. Measures of sun protection were reduced with children's increasing age. Skin cancer prevention campaigns should target the encouragement of sun protection for children also in outdoor activities of daily living, not only during a summer holiday on the beach.
    British Journal of Dermatology 01/2012; 166(4):803-10. · 3.76 Impact Factor
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    ABSTRACT: Chronic kidney disease (CKD) is increasingly recognized as a global health problem. The conditions leading to CKD, the health impact of CKD and the prognosis differ markedly between affected individuals. In particular, renal failure and cardiovascular mortality are competing risks for CKD patients. Opportunities for targeted intervention are very limited so far and require an improved understanding of the natural course of CKD, of the risk factors associated with various clinical end points and co-morbidities as well as of the underlying pathogenic mechanisms. The German Chronic Kidney Disease (GCKD) study is a prospective observational national cohort study. It aims to enrol a total of 5000 patients with CKD of various aetiologies, who are under nephrological care, and to follow them for up to 10 years. At the time of enrolment, male and female patients have an estimated glomerular filtration rate (eGFR) of 30-60 mL/min×1.73 m2 or overt proteinuria in the presence of an eGFR>60 mL/min×1.73 m2. Standardized collection of biomaterials, including DNA, serum, plasma and urine will allow identification and validation of biomarkers associated with CKD, CKD progression and related complications using hypothesis-driven and hypothesis-free approaches. Patient recruitment and follow-up is organized through a network of academic nephrology centres collaborating with practising nephrologists throughout the country. The GCKD study will establish one of the largest cohorts to date of CKD patients not requiring renal replacement therapy. Similarities in its design with other observational CKD studies, including cohorts that have already been established in the USA and Japan, will allow comparative and joint analyses to identify important ethnic and geographic differences and to enhance opportunities for identification of relevant risk factors and markers.
    Nephrology Dialysis Transplantation 08/2011; 27(4):1454-60. · 3.37 Impact Factor

Publication Stats

4k Citations
729.93 Total Impact Points


  • 1999–2014
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      • Department of Ophthalmology
      Erlangen, Bavaria, Germany
  • 2013
    • Hannover Medical School
      Hanover, Lower Saxony, Germany
  • 2000–2012
    • Universitätsklinikum Erlangen
      Erlangen, Bavaria, Germany
  • 2009
    • Klinikum Dortmund gGmbH
      Dortmund, North Rhine-Westphalia, Germany
  • 2008
    • Technische Universität Dortmund
      • Department of Business and Social Statistics
      Dortmund, North Rhine-Westphalia, Germany
  • 1991–2007
    • Georg-August-Universität Göttingen
      Göttingen, Lower Saxony, Germany
  • 2002–2005
    • Universität Heidelberg
      Heidelburg, Baden-Württemberg, Germany
  • 1991–2003
    • Universitätsmedizin Göttingen
      • • Division of Virology
      • • Department of Neurology
      • • Department of Medical Statistics
      Göttingen, Lower Saxony, Germany
  • 1997–2002
    • University of Hamburg
      • Institute for Occupational and Maritime Medicine
      Hamburg, Hamburg, Germany
  • 1995–2001
    • Universität Osnabrück
      Osnabrück, Lower Saxony, Germany
  • 1996–2000
    • Christian-Albrechts-Universität zu Kiel
      • Universitäts-Hautklinik Kiel
      Kiel, Schleswig-Holstein, Germany
  • 1994–1997
    • Universität Ulm
      Ulm, Baden-Württemberg, Germany