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Search Results: 1 - 10 of 2487 matches for " Marcel Wolbers "
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Considerations in the Design of Clinical Trials to Test Novel Entomological Approaches to Dengue Control
Marcel Wolbers,Immo Kleinschmidt,Cameron P. Simmons ,Christl A. Donnelly
PLOS Neglected Tropical Diseases , 2012, DOI: 10.1371/journal.pntd.0001937
Appropriateness of antibiotic treatment in intravenous drug users, a retrospective analysis
Dominik Mertz, Nina Viktorin, Marcel Wolbers, Gerd Laifer, Bernd Leimenstoll, Ursula Fluckiger, Manuel Battegay
BMC Infectious Diseases , 2008, DOI: 10.1186/1471-2334-8-42
Abstract: Retrospective study of all intravenous drug users hospitalized for treatment of infectious diseases and seen by infectious diseases specialists 1/2001–12/2006 at a university hospital. Treatment was administered according to guidelines when possible or to alternative treatment program in case of patients for whom adherence to standard protocols was not possible. Outcomes were defined with respect to appropriateness of treatment, hospital readmission, relapse and mortality rates. For statistical analysis adjustment for multiple hospitalizations of individual patients was made by using a generalized estimating equation.The total number of hospitalizations for infectious diseases was 344 among 216 intravenous drug users. Skin and soft tissue infections (n = 129, 37.5% of hospitalizations), pneumonia (n = 75, 21.8%) and endocarditis (n = 54, 15.7%) were most prevalent. Multiple infections were present in 25%. Treatment was according to standard guidelines for 78.5%, according to an alternative recommended program for 11.3%, and not according to guidelines or by the infectious diseases specialist advice for 10.2% of hospitalizations. Psychiatric disorders had a significant negative impact on compliance (compliance problems in 19.8% of hospitalizations) in multiple logistic regression analysis (OR = 2.4, CI 1.1–5.1, p = 0.03). The overall readmission rate and relapse rate within 30 days was 13.7% and 3.8%, respectively. Both non-compliant patient behavior (OR = 3.7, CI 1.3–10.8, p = 0.02) and non-adherence to treatment guidelines (OR = 3.3, CI 1.1–9.7, p = 0.03) were associated with a significant increase in the relapse rate in univariate analysis. In 590 person-years of follow-up, 24.6% of the patients died: 6.4% died during hospitalization (1.2% infection-related) and 13.6% of patients died after discharge.Appropriate antibiotic therapy according to standard guidelines in hospitalized intravenous drug users is generally practicable and successful. In a minority alternat
Sample size requirements for separating out the effects of combination treatments: Randomised controlled trials of combination therapy vs. standard treatment compared to factorial designs for patients with tuberculous meningitis
Marcel Wolbers, Dorothee Heemskerk, Tran Chau, Nguyen Yen, Maxine Caws, Jeremy Farrar, Jeremy Day
Trials , 2011, DOI: 10.1186/1745-6215-12-26
Abstract: We compared the two approaches using the design of a new trial in tuberculous meningitis as an example. In that trial the combination of 2 drugs added to standard treatment is assumed to reduce the hazard of death by 30% and the sample size of the combination trial to achieve 80% power is 750 patients. We calculated the power of corresponding factorial designs with one- to sixteen-fold the sample size of the combination trial depending on the contribution of each individual drug to the combination treatment effect and the strength of an interaction between the two.In the absence of an interaction, an eight-fold increase in sample size for the factorial design as compared to the combination trial is required to get 80% power to jointly detect effects of both drugs if the contribution of the less potent treatment to the total effect is at least 35%. An eight-fold sample size increase also provides a power of 76% to detect a qualitative interaction at the one-sided 10% significance level if the individual effects of both drugs are equal. Factorial designs with a lower sample size have a high chance to be underpowered, to show significance of only one drug even if both are equally effective, and to miss important interactions.Pragmatic combination trials of multiple interventions versus standard therapy are valuable in diseases with a limited patient pool if all interventions test the same treatment concept, it is considered likely that either both or none of the individual interventions are effective, and only moderate drug interactions are suspected. An adequately powered 2 × 2 factorial design to detect effects of individual drugs would require at least 8-fold the sample size of the combination trial.Current Controlled Trials ISRCTN61649292Tuberculous meningitis (TBM) is the most severe form of M. tuberculosis infection, and kills or disables more than half of those affected [1]. Effective new intervention strategies are thus urgently needed. The study hypothesis of
Intensity Frontier Computing at Fermilab
Stephen Wolbers
Physics , 2013,
Abstract: The Intensity Frontier (IF) experiments at Fermilab require computing, software, data handling, and infrastructure development for detector and beamline design and to extract maximum scientific output from the data. The emphasis of computing at Fermilab for many years has been on the Tevatron collider Run 2 experiments and CMS. Using the knowledge and experience gained from those experiments as well as new computing developments, preparations for computing for IF experiments are ramping up. There are many challenges in IF computing. These include event generators and detector simulation, beamline simulation, detector design and optimization, data acquisition, data handling, data analysis, and all of the associated services required. In this presentation the computing challenges and requirements will be described and the approaches being taken to address them will be shown.
Therapeutics for Dengue: Recommendations for Design and Conduct of Early-Phase Clinical Trials
Cameron P. Simmons ,Marcel Wolbers,Minh Nguyet Nguyen,Jamie Whitehorn,Pei Yong Shi,Paul Young,Rosemary Petric,Van Vinh Chau Nguyen,Jeremy Farrar,Bridget Wills
PLOS Neglected Tropical Diseases , 2012, DOI: 10.1371/journal.pntd.0001752
Pretreatment CD4 Cell Slope and Progression to AIDS or Death in HIV-Infected Patients Initiating Antiretroviral Therapy—The CASCADE Collaboration: A Collaboration of 23 Cohort Studies
Marcel Wolbers ,Abdel Babiker,Caroline Sabin,Jim Young,Maria Dorrucci,Geneviève Chêne,Cristina Mussini,Kholoud Porter,Heiner C. Bucher,on behalf of the CASCADE Collaboration
PLOS Medicine , 2010, DOI: 10.1371/journal.pmed.1000239
Abstract: Background CD4 cell count is a strong predictor of the subsequent risk of AIDS or death in HIV-infected patients initiating combination antiretroviral therapy (cART). It is not known whether the rate of CD4 cell decline prior to therapy is related to prognosis and should, therefore, influence the decision on when to initiate cART. Methods and Findings We carried out survival analyses of patients from the 23 cohorts of the CASCADE (Concerted Action on SeroConversion to AIDS and Death in Europe) collaboration with a known date of HIV seroconversion and with at least two CD4 measurements prior to initiating cART. For each patient, a pre-cART CD4 slope was estimated using a linear mixed effects model. Our primary outcome was time from initiating cART to a first new AIDS event or death. We included 2,820 treatment-na?ve patients initiating cART with a median (interquartile range) pre-cART CD4 cell decline of 61 (46–81) cells/μl per year; 255 patients subsequently experienced a new AIDS event or death and 125 patients died. In an analysis adjusted for established risk factors, the hazard ratio for AIDS or death was 1.01 (95% confidence interval 0.97–1.04) for each 10 cells/μl per year reduction in pre-cART CD4 cell decline. There was also no association between pre-cART CD4 cell slope and survival. Alternative estimates of CD4 cell slope gave similar results. In 1,731 AIDS-free patients with >350 CD4 cells/μl from the pre-cART era, the rate of CD4 cell decline was also not significantly associated with progression to AIDS or death (hazard ratio 0.99, 95% confidence interval 0.94–1.03, for each 10 cells/μl per year reduction in CD4 cell decline). Conclusions The CD4 cell slope does not improve the prediction of clinical outcome in patients with a CD4 cell count above 350 cells/μl. Knowledge of the current CD4 cell count is sufficient when deciding whether to initiate cART in asymptomatic patients. Please see later in the article for the Editors' Summary
Intensified treatment with high dose Rifampicin and Levofloxacin compared to standard treatment for adult patients with Tuberculous Meningitis (TBM-IT): protocol for a randomized controlled trial
Dorothee Heemskerk, Jeremy Day, Tran Chau, Nguyen Dung, Nguyen Yen, Nguyen Bang, Laura Merson, Piero Olliaro, Thomas Pouplin, Maxine Caws, Marcel Wolbers, Jeremy Farrar
Trials , 2011, DOI: 10.1186/1745-6215-12-25
Abstract: A randomized, double blind, placebo-controlled trial with two parallel arms, comparing standard Vietnamese national guideline treatment for tuberculous meningitis with standard treatment plus an increased dose of rifampicin (to 15 mg/kg/day total) and additional levofloxacin. The study will include 750 patients (375 per treatment group) including a minimum of 350 HIV-positive patients. The calculation assumes an overall mortality of 40% vs. 30% in the two arms, respectively (corresponding to a target hazard ratio of 0.7), a power of 80% and a two-sided significance level of 5%. Randomization ratio is 1:1. The primary endpoint is overall survival, i.e. time from randomization to death during a follow-up period of 9 months. Secondary endpoints are: neurological disability at 9 months, time to new neurological event or death, time to new or recurrent AIDS-defining illness or death (in HIV-positive patients only), severe adverse events, and rate of treatment interruption for adverse events.Currently very few options are available for the treatment of TBM and the mortality rate remains unacceptably high with severe disabilities seen in many of the survivors. This trial is based on the hypothesis that current anti-mycobacterial treatment schedules for TBM are not potent enough and that outcomes will be improved by increasing the CSF penetrating power of this regimen by optimising dosage and using additional drugs with better CSF penetration.International Standard Randomised Controlled Trial Number ISRCTN61649292Driven in part by the HIV epidemic, tuberculosis (TB) is a major global health problem. Of all the syndromes caused by Mycobacterium tuberculosis (Mtb), tuberculous meningitis (TBM) is the most severe. Almost all patients with untreated TBM die. Since the introduction of antibiotic treatment with streptomycin for TB in the 1950's the death rate has declined [1]. However morbidity and mortality overall are still high. In Vietnam the death rate in HIV negative patien
Assessment of Microalbuminuria for Early Diagnosis and Risk Prediction in Dengue Infections
Nguyen Thi Hanh Tien, Phung Khanh Lam, Huynh Thi Le Duyen, Tran Van Ngoc, Phan Thi Thanh Ha, Nguyen Tan Thanh Kieu, Cameron Simmons, Marcel Wolbers, Bridget Wills
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0054538
Abstract: Background Dengue is the most important arboviral infection of humans. Following an initial febrile period, a small proportion of infected patients develop a vasculopathy, with children at particular risk for severe vascular leakage and shock. Differentiation between dengue and other common childhood illnesses is difficult during the early febrile phase, and risk prediction for development of shock is poor. The presence of microalbuminuria is recognized as a useful early predictor for subsequent complications in a number of other disorders with vascular involvement. Significant proteinuria occurs in association with dengue shock syndrome and it is possible that early-phase microalbuminuria may be helpful both for diagnosis of dengue and for identification of patients likely to develop severe disease. Methodology/Principal Findings We measured formal urine albumin to creatinine ratios (UACRs) in daily samples obtained from a large cohort of children with suspected dengue recruited at two outpatient clinics in Ho Chi Minh City, Vietnam. Although UACRs were increased in the 465 confirmed dengue patients, with a significant time trend showing peak values around the critical period for dengue-associated plasma leakage, urine albumin excretion was also increased in the comparison group of 391 patients with other febrile illnesses (OFI). The dengue patients generally had higher UACRs than the OFI patients, but microalbuminuria, using the conventional cutoff of 30 mg albumin/g creatinine discriminated poorly between the two diagnostic groups in the early febrile phase. Secondly UACRs did not prove useful in predicting either development of warning signs for severe dengue or need for hospitalization. Conclusion/Significance Low-level albuminuria is common, even in relatively mild dengue infections, but is also present in many OFIs. Simple point-of-care UACR tests are unlikely to be useful for early diagnosis or risk prediction in dengue endemic areas.
L1 Educational Studies in Language and Literature , 2010,
Abstract: This study investigated the use of ASL and print-based sign in the development of English writing fluencyand writing independence among deaf, middle school students. ASL was the primary languagethrough which students engaged in higher-level thinking, problem solving and meaning making. Printbasedsign was used for rereading the collaboratively constructed English text. Mixed method approacheswere utilized. First, a pretest-posttest control group design investigated whether students receiving theinstruction made significantly greater gains compared to non-receivers with length of text—one indicatorof writing fluency. There were a total of 33 students, 16 in the treatment group and 17 in the comparisongroup. The intervention lasted a total of 8 weeks, during which the treatment teacher guided the collaborativeconstruction of two English report papers. The comparison group continued with its usual writinginstruction and had equal instructional time. The analysis of variance (ANOVA) for length was statisticallysignificant with a large effect size (d=1.53). Additionally, qualitative data demonstrated ways inwhich three very different classes in the treatment group gained greater English competency and fluency.Further development of ASL as L1 was deemed a necessary component for students with language delays.All students exhibited progressively more independence with writing over time.
Clinical Features of Dengue in a Large Vietnamese Cohort: Intrinsically Lower Platelet Counts and Greater Risk for Bleeding in Adults than Children
Trung Dinh The ,Thao Le Thi Thu,Dung Nguyen Minh,Ngoc Tran Van,Hien Tran Tinh,Chau Nguyen Van Vinh,Marcel Wolbers,Tam Dong Thi Hoai,Jeremy Farrar,Cameron Simmons,Bridget Wills
PLOS Neglected Tropical Diseases , 2012, DOI: 10.1371/journal.pntd.0001679
Abstract: Background As dengue spreads to new geographical regions and the force of infection changes in existing endemic areas, a greater breadth of clinical presentations is being recognised. Clinical experience suggests that adults manifest a pattern of complications different from those observed in children, but few reports have described the age-related spectrum of disease in contemporaneous groups of patients recruited at the same geographical location. Methodology/Principal Findings Using detailed prospectively collected information from ongoing studies that encompass the full spectrum of hospitalised dengue cases admitted to a single hospital in southern Vietnam, we compared clinical and laboratory features, management, and outcome for 647 adults and 881 children with confirmed dengue. Signs of vascular leakage and shock were more frequent and more severe in children than adults, while bleeding manifestations and organ involvement were more common in adults. Additionally, adults experienced significantly more severe thrombocytopenia. Secondary infection but not serotype was independently associated with greater thrombocytopenia, although with a smaller effect than age-group. The effect of age-group on platelet count was also apparent in the values obtained several weeks after recovery, indicating that healthy adults have intrinsically lower counts compared to children. Conclusions/Significance There are clear distinctions between adults and children in the pattern of complications seen in association with dengue infection, and these depend partly on intrinsic age-dependent physiological differences. Knowledge of such differences is important to inform research on disease pathogenesis, as well as to encourage development of management guidelines that are appropriate to the age-groups at risk.
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