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1.
Bioengineering (Basel) ; 10(11)2023 Nov 16.
Article in English | MEDLINE | ID: mdl-38002444

ABSTRACT

Type 2 diabetes mellitus (T2D) poses a significant global health challenge and demands effective self-management strategies, including continuous blood glucose monitoring (CGM) and lifestyle adaptations. While CGM offers real-time glucose level assessment, the quest for minimizing trauma and enhancing convenience has spurred the need to explore non-invasive alternatives for monitoring vital signs in patients with T2D. Objective: This systematic review is the first that explores the current literature and critically evaluates the use and reporting of non-invasive wearable devices for monitoring vital signs in patients with T2D. Methods: Employing the PRISMA and PICOS guidelines, we conducted a comprehensive search to incorporate evidence from relevant studies, focusing on randomized controlled trials (RCTs), systematic reviews, and meta-analyses published since 2017. Of the 437 publications identified, seven were selected based on predetermined criteria. Results: The seven studies included in this review used various sensing technologies, such as heart rate monitors, accelerometers, and other wearable devices. Primary health outcomes included blood pressure measurements, heart rate, body fat percentage, and cardiorespiratory endurance. Non-invasive wearable devices demonstrated potential for aiding T2D management, albeit with variations in efficacy across studies. Conclusions: Based on the low number of studies with higher evidence levels (i.e., RCTs) that we were able to find and the significant differences in design between these studies, we conclude that further evidence is required to validate the application, efficacy, and real-world impact of these wearable devices. Emphasizing transparency in bias reporting and conducting in-depth research is crucial for fully understanding the implications and benefits of wearable devices in T2D management.

2.
Cell Death Dis ; 12(12): 1162, 2021 12 15.
Article in English | MEDLINE | ID: mdl-34911941

ABSTRACT

Resistance against radio(chemo)therapy-induced cell death is a major determinant of oncological treatment failure and remains a perpetual clinical challenge. The underlying mechanisms are manifold and demand for comprehensive, cancer entity- and subtype-specific examination. In the present study, resistance against radiotherapy was systematically assessed in a panel of human head-and-neck squamous cell carcinoma (HNSCC) cell lines and xenotransplants derived thereof with the overarching aim to extract master regulators and potential candidates for mechanism-based pharmacological targeting. Clonogenic survival data were integrated with molecular and functional data on DNA damage repair and different cell fate decisions. A positive correlation between radioresistance and early induction of HNSCC cell senescence accompanied by NF-κB-dependent production of distinct senescence-associated cytokines, particularly ligands of the CXCR2 chemokine receptor, was identified. Time-lapse microscopy and medium transfer experiments disclosed the non-cell autonomous, paracrine nature of these mechanisms, and pharmacological interference with senescence-associated cytokine production by the NF-κB inhibitor metformin significantly improved radiotherapeutic performance in vitro and in vivo. With regard to clinical relevance, retrospective analyses of TCGA HNSCC data and an in-house HNSCC cohort revealed that elevated expression of CXCR2 and/or its ligands are associated with impaired treatment outcome. Collectively, our study identifies radiation-induced tumor cell senescence and the NF-κB-dependent production of distinct senescence-associated cytokines as critical drivers of radioresistance in HNSCC whose therapeutic targeting in the context of multi-modality treatment approaches should be further examined and may be of particular interest for the subgroup of patients with elevated expression of the CXCR2/ligand axis.


Subject(s)
Cellular Senescence , Head and Neck Neoplasms , Radiation Tolerance , Receptors, Interleukin-8B , Squamous Cell Carcinoma of Head and Neck , Cell Line, Tumor , Cytokines , Gene Expression Regulation, Neoplastic , Head and Neck Neoplasms/radiotherapy , Humans , Ligands , NF-kappa B , Receptors, Interleukin-8B/metabolism , Retrospective Studies , Squamous Cell Carcinoma of Head and Neck/radiotherapy
3.
Age Ageing ; 50(6): 2123-2132, 2021 11 10.
Article in English | MEDLINE | ID: mdl-34473822

ABSTRACT

OBJECTIVES: To reduce infections with Clostridioides difficile (CDI) in geriatric patients by interventions easily implementable in standard clinical care. METHODS: Prevalence and incidence of CDI between January 2015 and February 2020 were analysed (n = 25,311 patients). Pre-intervention status was assessed from April 2016 to March 2017 (n = 4,922). Between May 2017 and August 2019, a monocentric interventional crossover study (n = 4,655) was conducted including standard care and three interventions: (A) sporicidal cleaning of hospital wards, (B) probiotics and (C) improvement in personal hygiene for CDI patients. This was followed by a multicentric comparison of the interventional bundle (A + B + C) between September 2019 and February 2020 (n = 2,593) with the pre-intervention phase. In 98 CDI cases and matched controls individual risk factors for the development of CDI were compared. RESULTS: Time series analyses of CDI cases revealed a reduction in the prevalence of CDI in all three participating centres prior to the multicentric intervention phase. In the monocentric phase, no effect of individual interventions on CDI prevalence was identified. However, an aggregated analysis of CDI cases comparing the pre-intervention and the multicentric phase revealed a significant reduction in CDI prevalence. Risk factors for the development of CDI included use of antibiotics, anticoagulants, previous stay in long-term care facilities, prior hospital admissions, cardiac and renal failure, malnutrition and anaemia. CONCLUSIONS: The observed reduction in CDI may be attributed to heightened awareness of the study objectives and specific staff training. Individual interventions did not appear to reduce CDI prevalence. A further randomised trial would be necessary to confirm whether the bundle of interventions is truly effective.


Subject(s)
Clostridioides difficile , Clostridium Infections , Cross Infection , Aged , Clostridioides , Clostridium Infections/diagnosis , Clostridium Infections/epidemiology , Cross Infection/diagnosis , Cross Infection/epidemiology , Cross Infection/prevention & control , Cross-Over Studies , Humans , Quality Improvement
4.
Emerg Infect Dis ; 26(8)2020 08.
Article in English | MEDLINE | ID: mdl-32687038

ABSTRACT

We investigated sporadic Creutzfeldt-Jakob disease (sCJD) among physicians in Germany by analyzing occupational information of patients with sCJD recorded by the German CJD Surveillance Unit (1993-2005; 1,250 patients, of whom 4 [0.32%] were physicians) and the National Reference Center for Human Spongiform Encephalopathies (2006-2016; 1,491 patients, of whom 13 [0.87%] were physicians). Among the physicians, we did not identify any neurologists, neurosurgeons, psychiatrists, or pathologists. A cumulative sum test showed an increase in reported physicians over time. Data for 2017-2018 indicated an increased rate of physicians among all notified sCJD cases (5/239 [2.1%]) when we used the total population of Germany as control group. Our data suggest the possibility of an increased risk for sCJD among physicians in Germany. However, we can only speculate about the reasons, and larger multinational studies are needed to replicate the finding and to clarify whether this finding is a general or a country-specific phenomenon.


Subject(s)
Creutzfeldt-Jakob Syndrome , Physicians , Prion Diseases , Creutzfeldt-Jakob Syndrome/epidemiology , Germany/epidemiology , Humans
5.
Pharm Stat ; 18(2): 166-183, 2019 03.
Article in English | MEDLINE | ID: mdl-30458579

ABSTRACT

The analysis of adverse events (AEs) is a key component in the assessment of a drug's safety profile. Inappropriate analysis methods may result in misleading conclusions about a therapy's safety and consequently its benefit-risk ratio. The statistical analysis of AEs is complicated by the fact that the follow-up times can vary between the patients included in a clinical trial. This paper takes as its focus the analysis of AE data in the presence of varying follow-up times within the benefit assessment of therapeutic interventions. Instead of approaching this issue directly and solely from an analysis point of view, we first discuss what should be estimated in the context of safety data, leading to the concept of estimands. Although the current discussion on estimands is mainly related to efficacy evaluation, the concept is applicable to safety endpoints as well. Within the framework of estimands, we present statistical methods for analysing AEs with the focus being on the time to the occurrence of the first AE of a specific type. We give recommendations which estimators should be used for the estimands described. Furthermore, we state practical implications of the analysis of AEs in clinical trials and give an overview of examples across different indications. We also provide a review of current practices of health technology assessment (HTA) agencies with respect to the evaluation of safety data. Finally, we describe problems with meta-analyses of AE data and sketch possible solutions.


Subject(s)
Clinical Trials as Topic/methods , Data Interpretation, Statistical , Drug-Related Side Effects and Adverse Reactions/diagnosis , Clinical Trials as Topic/statistics & numerical data , Endpoint Determination , Follow-Up Studies , Humans , Research Design , Technology Assessment, Biomedical/methods , Time Factors
6.
Oncoimmunology ; 8(1): e1523097, 2019.
Article in English | MEDLINE | ID: mdl-30546963

ABSTRACT

The major goal of radiotherapy is the induction of tumor cell death. Additionally, radiotherapy can function as in situ cancer vaccination by exposing tumor antigens and providing adjuvants for anti-tumor immune priming. In this regard, the mode of tumor cell death and the repertoire of released damage-associated molecular patterns (DAMPs) are crucial. However, optimal dosing and fractionation of radiotherapy remain controversial. Here, we examined the initial steps of anti-tumor immune priming by different radiation regimens (20 Gy, 4 × 2 Gy, 2 Gy, 0 Gy) with cell lines of triple-negative breast cancer in vitro and in vivo. Previously, we have shown that especially high single doses (20 Gy) induce a delayed type of primary necrosis with characteristics of mitotic catastrophe and plasma membrane disintegration. Now, we provide evidence that protein DAMPs released by these dying cells stimulate sequential recruitment of neutrophils and monocytes in vivo. Key players in this regard appear to be endothelial cells revealing a distinct state of activation upon exposure to supernatants of irradiated tumor cells as characterized by high surface expression of adhesion molecules and production of a discrete cytokine/chemokine pattern. Furthermore, irradiated tumor cell-derived protein DAMPs enforced differentiation and maturation of dendritic cells as hallmarked by upregulation of co-stimulatory molecules and improved T cell-priming. Consistently, a recurring pattern was observed: The strongest effects were detected with 20 Gy-irradiated cells. Obviously, the initial steps of radiotherapy-induced anti-tumor immune priming are preferentially triggered by high single doses - at least in models of triple-negative breast cancer.

7.
Orphanet J Rare Dis ; 13(1): 186, 2018 10 25.
Article in English | MEDLINE | ID: mdl-30359266

ABSTRACT

Where there are a limited number of patients, such as in a rare disease, clinical trials in these small populations present several challenges, including statistical issues. This led to an EU FP7 call for proposals in 2013. One of the three projects funded was the Innovative Methodology for Small Populations Research (InSPiRe) project. This paper summarizes the main results of the project, which was completed in 2017.The InSPiRe project has led to development of novel statistical methodology for clinical trials in small populations in four areas. We have explored new decision-making methods for small population clinical trials using a Bayesian decision-theoretic framework to compare costs with potential benefits, developed approaches for targeted treatment trials, enabling simultaneous identification of subgroups and confirmation of treatment effect for these patients, worked on early phase clinical trial design and on extrapolation from adult to pediatric studies, developing methods to enable use of pharmacokinetics and pharmacodynamics data, and also developed improved robust meta-analysis methods for a small number of trials to support the planning, analysis and interpretation of a trial as well as enabling extrapolation between patient groups. In addition to scientific publications, we have contributed to regulatory guidance and produced free software in order to facilitate implementation of the novel methods.


Subject(s)
Rare Diseases , Research Design/statistics & numerical data , Humans
8.
Drugs Aging ; 35(9): 859-869, 2018 09.
Article in English | MEDLINE | ID: mdl-30066299

ABSTRACT

BACKGROUND: The benefit of anticoagulative treatment to prevent thromboembolism has been established in patients with atrial fibrillation and flutter of all age groups. Traditionally, anticoagulation was underused in geriatric patients with atrial fibrillation and flutter. OBJECTIVE: The aim of this study was to assess whether the broad introduction of non-vitamin K antagonist oral anticoagulants into clinical medicine has changed the rate of older patients treated with anticoagulants for atrial fibrillation and flutter. METHODS: Hospitalized geriatric patients treated in 2015 were retrospectively studied for the presence of atrial fibrillation and flutter and the use or non-use of anticoagulation. The risk of stroke and the indication for permanent anticoagulation were assessed using the CHA2DS2-VASc score. RESULTS: Five hundred and twelve of 1320 patients showed a clear indication for therapeutic anticoagulation (38.8%). Of these, 431 patients (84.2%) had long-standing persistent (> 1 year)/permanent atrial fibrillation and flutter or paroxysmal/persistent (> 7 days) atrial fibrillation and flutter as well as CHA2DS2-VASc scores of ≥ 2 in men and ≥ 3 in women. In this group, 378 patients (87.7%) received anticoagulative treatment. Of all patients anticoagulated for atrial fibrillation and flutter, 221 received non-vitamin K antagonist oral anticoagulants (58.5%), 176 received apixaban (46.6%), 32 received rivaroxaban (8.5%), and 13 received dabigatran (3.4%). One hundred and seven patients received the vitamin K antagonist phenprocoumon (28.3%) and 50 patients received high-dose low-molecular-weight heparins (13.2%). In 21 patients (5.6% of all anticoagulated patients with atrial fibrillation and flutter), hemorrhagic complications were documented. Eleven complications (52.4; 5.0% of all patients treated with non-vitamin K antagonist oral anticoagulants) occurred during treatment with non-vitamin K antagonist oral anticoagulants, four (19.0%) during anticoagulation with phenprocoumon and six (28.6%) during treatment with low-molecular-weight heparins. No intracranial hemorrhages and no fatal bleeding events occurred. CONCLUSION: The introduction of non-vitamin K antagonist oral anticoagulants and an increased awareness of their benefits led to an increased use of anticoagulation from 52.8% (2011) to 87.7% (2015) in geriatric patients with atrial fibrillation and flutter at our institution.


Subject(s)
Anticoagulants/therapeutic use , Atrial Fibrillation/drug therapy , Geriatrics , Hospitalization , Administration, Oral , Aged , Anticoagulants/administration & dosage , Atrial Fibrillation/complications , Female , Humans , Male , Middle Aged , Retrospective Studies , Stroke/complications , Thromboembolism/complications , Thromboembolism/prevention & control
9.
Orphanet J Rare Dis ; 11: 16, 2016 Feb 20.
Article in English | MEDLINE | ID: mdl-26897367

ABSTRACT

BACKGROUND: Randomized controlled trials (RCTs) are the gold standard design of clinical research to assess interventions. However, RCTs cannot always be applied for practical or ethical reasons. To investigate the current practices in rare diseases, we review evaluations of therapeutic interventions in paediatric multiple sclerosis (MS) and Creutzfeldt-Jakob disease (CJD). In particular, we shed light on the endpoints used, the study designs implemented and the statistical methodologies applied. METHODS: We conducted literature searches to identify relevant primary studies. Data on study design, objectives, endpoints, patient characteristics, randomization and masking, type of intervention, control, withdrawals and statistical methodology were extracted from the selected studies. The risk of bias and the quality of the studies were assessed. RESULTS: Twelve (seven) primary studies on paediatric MS (CJD) were included in the qualitative synthesis. No double-blind, randomized placebo-controlled trial for evaluating interventions in paediatric MS has been published yet. Evidence from one open-label RCT is available. The observational studies are before-after studies or controlled studies. Three of the seven selected studies on CJD are RCTs, of which two received the maximum mark on the Oxford Quality Scale. Four trials are controlled observational studies. CONCLUSIONS: Evidence from double-blind RCTs on the efficacy of treatments appears to be variable between rare diseases. With regard to paediatric conditions it remains to be seen what impact regulators will have through e.g., paediatric investigation plans. Overall, there is space for improvement by using innovative trial designs and data analysis techniques.


Subject(s)
Creutzfeldt-Jakob Syndrome/diagnosis , Creutzfeldt-Jakob Syndrome/drug therapy , Multiple Sclerosis/diagnosis , Multiple Sclerosis/drug therapy , Humans , Randomized Controlled Trials as Topic
10.
Radiat Oncol ; 11: 11, 2016 Jan 28.
Article in English | MEDLINE | ID: mdl-26822015

ABSTRACT

BACKGROUND: The most frequently used method to quantitatively describe the response to ionizing irradiation in terms of clonogenic survival is the linear-quadratic (LQ) model. In the LQ model, the logarithm of the surviving fraction is regressed linearly on the radiation dose by means of a second-degree polynomial. The ratio of the estimated parameters for the linear and quadratic term, respectively, represents the dose at which both terms have the same weight in the abrogation of clonogenic survival. This ratio is known as the α/ß ratio. However, there are plausible scenarios in which the α/ß ratio fails to sufficiently reflect differences between dose-response curves, for example when curves with similar α/ß ratio but different overall steepness are being compared. In such situations, the interpretation of the LQ model is severely limited. METHODS: Colony formation assays were performed in order to measure the clonogenic survival of nine human pancreatic cancer cell lines and immortalized human pancreatic ductal epithelial cells upon irradiation at 0-10 Gy. The resulting dataset was subjected to LQ regression and non-linear log-logistic regression. Dimensionality reduction of the data was performed by cluster analysis and principal component analysis. RESULTS: Both the LQ model and the non-linear log-logistic regression model resulted in accurate approximations of the observed dose-response relationships in the dataset of clonogenic survival. However, in contrast to the LQ model the non-linear regression model allowed the discrimination of curves with different overall steepness but similar α/ß ratio and revealed an improved goodness-of-fit. Additionally, the estimated parameters in the non-linear model exhibit a more direct interpretation than the α/ß ratio. Dimensionality reduction of clonogenic survival data by means of cluster analysis was shown to be a useful tool for classifying radioresistant and sensitive cell lines. More quantitatively, principal component analysis allowed the extraction of scores of radioresistance, which displayed significant correlations with the estimated parameters of the regression models. CONCLUSIONS: Undoubtedly, LQ regression is a robust method for the analysis of clonogenic survival data. Nevertheless, alternative approaches including non-linear regression and multivariate techniques such as cluster analysis and principal component analysis represent versatile tools for the extraction of parameters and/or scores of the cellular response towards ionizing irradiation with a more intuitive biological interpretation. The latter are highly informative for correlation analyses with other types of data, including functional genomics data that are increasingly being generated.


Subject(s)
Radiotherapy/methods , Cell Line, Tumor , Cell Survival/radiation effects , Cluster Analysis , Computer Simulation , Dose Fractionation, Radiation , Dose-Response Relationship, Radiation , Humans , Linear Models , Nonlinear Dynamics , Pancreatic Neoplasms/radiotherapy , Principal Component Analysis , Radiation Tolerance/physiology , Regression Analysis , Software , Statistics as Topic
11.
Cancer Lett ; 365(2): 211-22, 2015 Sep 01.
Article in English | MEDLINE | ID: mdl-26044951

ABSTRACT

Radiotherapy is an essential part of multi-modal treatment for soft tissue sarcomas. Treatment failure is commonly attributed to radioresistance, but comprehensive analyses of radiosensitivity are not available, and suitable biomarkers or candidates for targeted radiosensitization are scarce. Here, we systematically analyzed the intrinsic radioresistance of a panel of soft tissue sarcoma cell lines, and extracted scores of radioresistance by principal component analysis (PCA). To identify molecular markers of radioresistance, transcriptomic profiling of DNA damage response regulators was performed. The expression levels of HSP90 and its clients ATR, ATM, and NBS1 revealed strong, positive correlations with the PCA-derived radioresistance scores. Their functional involvement was addressed by HSP90 inhibition, which preferentially sensitized radioresistant sarcoma cells and was accompanied by delayed γ-H2AX foci clearance and HSP90 client protein degradation. The induction of apoptosis and necrosis was not significantly enhanced, but increased levels of basal and irradiation-induced senescence upon HSP90 inhibition were detected. Finally, evaluation of our findings in the TCGA soft tissue sarcoma cohort revealed elevated expression levels of HSP90, ATR, ATM, and NBS1 in a relevant subset of cases with particularly poor prognosis, which might preferentially benefit from HSP90 inhibition in combination with radiotherapy in the future.


Subject(s)
HSP90 Heat-Shock Proteins/antagonists & inhibitors , Radiation Tolerance/genetics , Sarcoma/radiotherapy , Soft Tissue Neoplasms/radiotherapy , Apoptosis/radiation effects , Ataxia Telangiectasia Mutated Proteins/biosynthesis , Cell Cycle Proteins/biosynthesis , Cell Line, Tumor , Cell Survival/radiation effects , Cellular Senescence/genetics , Combined Modality Therapy , DNA Damage/genetics , DNA Repair/genetics , HSP90 Heat-Shock Proteins/biosynthesis , HSP90 Heat-Shock Proteins/metabolism , Histones/metabolism , Humans , Nuclear Proteins/biosynthesis , Principal Component Analysis
12.
J Am Acad Audiol ; 26(1): 68-79, 2015 Jan.
Article in English | MEDLINE | ID: mdl-25597462

ABSTRACT

BACKGROUND: In-situ audiometry is a hearing aid feature that enables the measurement of hearing threshold levels through the hearing instrument using the built-in sound generator and the hearing aid receiver. This feature can be used in hearing aid fittings instead of conventional pure-tone audiometry (PTA), particularly in places where no standard audiometric equipment is available. Differences between conventional and in-situ thresholds are described and discussed for some particular hearing aids. No previous investigation has measured and compared these differences for a number of current hearing aid models by various manufacturers across a wide range of hearing losses. PURPOSE: The purpose of this study was to perform a model-based comparison of conventionally and in-situ measured hearing thresholds. Data were collected for a range of hearing aid devices to study and generalize the effects that may occur under clinical conditions. RESEARCH DESIGN: Research design was an experimental and regression study. STUDY SAMPLE: A total of 30 adults with sensorineural hearing loss served as test persons. They were assigned to three subgroups of 10 subjects with mild (M), moderate to severe (MS), and severe (S) sensorineural hearing loss. INTERVENTION: All 30 test persons underwent both conventional PTA and in-situ audiometry with four hearing aid models by various manufacturers. DATA COLLECTION AND ANALYSIS: The differences between conventionally and in-situ measured hearing threshold levels were calculated and evaluated by an exploratory data analysis followed by a sophisticated statistical modeling process. RESULTS: At 500 and 1500 Hz, almost all threshold differences (conventional PTA minus in-situ data) were negative, i.e., in the low to mid frequencies, hearing loss was overestimated by most devices relative to PTA. At 4000 Hz, the majority of differences (7 of 12) were positive, i.e., in the frequency range above 1500 Hz, hearing loss was frequently underestimated. As hearing loss increased (M→MS→S), the effect of the underestimation decreased. At 500 and 1500 Hz, Resound devices showed the smallest threshold deviations, followed by Phonak, Starkey, and Oticon instruments. At 4000 Hz, this observed pattern partly disappeared and Starkey and Oticon devices showed a reversed effect with increasing hearing loss (M→MS→S). Because of high standard errors for the estimates, only a few explicit rankings of the devices could be established based on significant threshold differences (5% level). CONCLUSIONS: Differences between conventional PTA and in-situ threshold levels may be attributed to (1) frequency, (2) device/hearing loss, and (3) calibration/manufacturer effects. Frequency effects primarily resulting in an overestimation of hearing loss by in-situ audiometry in the low and mid frequencies are mainly due to sound drain-off through vents and leaks. Device/hearing loss effects may be due to leakage as well as boundary effects because in-situ audiometry is confined to a limited measurement range. Finally, different calibration approaches may result in different offset levels between PTA and in-situ audiometry calibration. In some cases, the observed threshold differences of up to 10-15 dB may translate to varied hearing aid fittings for the same user depending on how hearing threshold levels were measured.


Subject(s)
Audiometry, Pure-Tone/methods , Auditory Threshold/physiology , Hearing Aids , Hearing Loss, Sensorineural/rehabilitation , Speech Perception/physiology , Adult , Female , Hearing Loss, Sensorineural/physiopathology , Humans , Male
13.
Am J Epidemiol ; 177(5): 474-86, 2013 Mar 01.
Article in English | MEDLINE | ID: mdl-23403987

ABSTRACT

In this paper, we propose new methods for investigating the extent of heterogeneity in effective contact rates relevant to the transmission of infections. These methods exploit the correlations between ages at infection for different infections within individuals. The methods are developed for serological surveys, which provide accessible individual data on several infections, and are applied to a wide range of infections. We find that childhood infections are often highly correlated within individuals in early childhood, with the correlations persisting into adulthood only for infections sharing a transmission route. We discuss 2 applications of the methods: 1) to making inferences about routes of transmission when these are unknown or uncertain and 2) to estimating epidemiologic parameters such as the basic reproduction number and the critical immunization threshold. Two examples of such applications are presented: elucidating the transmission route of polyomaviruses BK and JC and estimating the basic reproduction number and critical immunization coverage of varicella-zoster infection in Belgium, Italy, Poland, and England and Wales. We speculate that childhood correlations stem from confounding of different transmission routes and represent heterogeneity in childhood circumstances, notably nursery-school attendance. In contrast, it is suggested that correlations in adulthood are route-specific.


Subject(s)
Disease Transmission, Infectious , Epidemiologic Methods , Vaccination/statistics & numerical data , Basic Reproduction Number , Humans , Models, Biological , Seroepidemiologic Studies , Serologic Tests , Statistics as Topic
14.
Biostatistics ; 14(3): 528-40, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23266419

ABSTRACT

The basic reproduction number of an infection in a given population, R0, is inflated by individual heterogeneity in contact rates. Recently, new methods for estimating R0 using social contact data and serological survey data have been proposed. These methods, like most of their predecessors, ignore individual heterogeneity, and are sensitive to perturbation of the contact function. Using a frailty framework, we derive expressions for R0 in the presence of age-varying heterogeneity. In this case, R0 is the spectral radius of a population version of the next generation operator, which involves the variance function of the age-dependent frailty. This variance can be estimated within a shared frailty framework from paired data on two infections transmitted by the same route. We propose two estimators of R0 for infections in endemic equilibrium. We investigate their performance by simulation, and find that one is generally less efficient but more robust than the other to perturbation of the effective contact function. These methods are applied to data on varicella zoster virus infection from two European countries.


Subject(s)
Basic Reproduction Number/statistics & numerical data , Communicable Diseases/transmission , Models, Statistical , Adolescent , Biostatistics , Chickenpox/epidemiology , Chickenpox/transmission , Child , Child, Preschool , Communicable Diseases/epidemiology , Disease Outbreaks , Europe/epidemiology , Humans , Infant , Young Adult
15.
Biostatistics ; 13(4): 665-79, 2012 Sep.
Article in English | MEDLINE | ID: mdl-22529251

ABSTRACT

In this paper, a new measure for assessing the temporal variation in the strength of association in bivariate current status data is proposed. This novel measure is relevant for shared frailty models. We show that this measure is particularly convenient, owing to its connection with the relative frailty variance and its interpretability in suggesting appropriate frailty models. We introduce a method of estimation and standard errors for this measure. We discuss its properties and compare it to an existing measure of association applicable to current status data. Small sample performance of the measure in realistic scenarios is investigated using simulations. The methods are illustrated with bivariate serological survey data on a pair of infections, where the time-varying association is likely to represent heterogeneities in activity levels and/or susceptibility to infection.


Subject(s)
Data Interpretation, Statistical , Models, Statistical , Survival Analysis , Computer Simulation , Helicobacter Infections/blood , Helicobacter Infections/immunology , Helicobacter Infections/microbiology , Helicobacter pylori/immunology , Humans , Toxoplasma/immunology , Toxoplasmosis/blood , Toxoplasmosis/immunology , Toxoplasmosis/parasitology
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