Thomas R Fleming

University of Washington Seattle, Seattle, Washington, United States

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Publications (60)578.52 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Background In pulmonary arterial hypertension (PAH), adding oral sildenafil to intravenous (IV) epoprostenol improved 6-minute walk distance (6MWD) and haemodynamics and delayed time to clinical worsening in a 16-week randomised, placebo-controlled trial (PACES-1). Methods Patients completing PACES-1 could receive sildenafil (titrated to 80 mg TID as tolerated) in an open-label extension study (PACES-2) for ≥3 years; additional therapy was added per investigator judgment. Survival and changes from PACES-1 baseline in World Health Organization functional class (FC) and 6MWD were captured. Results In an open-label setting, an effort-dependent outcome measure, 6MWD, was known to have improved or to have been maintained in 59%, 44%, and 33% of patients at 1, 2, and 3 years, respectively; FC was known to have improved or to have been maintained in 73%, 59%, and 46%. At 3 years, 66% of patients were known to be alive, 24% were known to have died, and 10% were lost to follow-up. Patients with PACES-1 baseline 6MWD <325 m without 6MWD improvement during the first 20 weeks of sildenafil treatment subsequently had poorer survival. Conclusion While reliable assessments of safety and efficacy require a long-term randomised trial, addition of sildenafil to background IV epoprostenol therapy appeared generally to be well tolerated in PAH patients.
    The Journal of heart and lung transplantation: the official publication of the International Society for Heart Transplantation 07/2014; · 5.61 Impact Factor
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    ABSTRACT: Abstract Background: Data Monitoring Committees (DMCs) have important roles in safeguarding patient interests and enhancing trial integrity and credibility. To effectively fulfill their responsibilities, DMCs should be independent of study sponsors, study investigators and caregivers managing study participants. Unfortunately, in real world settings where DMCs are in place, there are some practices that threaten to diminish the level of independence of these committees. Purpose: Our goal is to inform those who have responsibilities in implementing the DMC process, or who are relying upon or participating as members, about some evolving issues that can meaningfully impact the DMC's ability to remain sufficiently independent to be able to effectively address its mission. Methods: We identified specific issues that are likely to be very important, both now and in the near future, with regard to the actual level of independence of DMCs. We provide insights into how these issues have emerged and to their importance, and provide recommendations for approaches to effectively address them. Results: Among the recommendations: a DMC Charter should outline the roles and responsibilities of the DMC without appearing to be a legal contract; the meetings of the DMC should be led by its chair, ideally with a meeting format that ensures independence from the investigators and sponsor; the DMC and those having leadership roles in the monitoring process should have adequate training and experience; procedures should be in place to enable the DMC to have access to interim safety and efficacy data that are accurate, current and comprehensive; these data should be presented to the DMC unblinded by treatment group, while being kept confidential from all others; DMC recommendations should be developed through consensus development rather than by casting votes; creative approaches are needed for the engagement of DMC members to increase the transparency that they are neither employees of, nor consultants to, the sponsor of the trial; meaningful conflicts of interest should be identified and addressed; finally, members of DMCs should have adequate indemnification that provides effective protection. Conclusions: The independence of DMCs is of integral importance to their ability to effectively carry out their responsibilities. We need wider recognition of the influence of some practices that could diminish the independence of DMCs, and a commitment to identify and implement approaches to enhance their independence.
    Journal of Biopharmaceutical Statistics 06/2014; · 0.72 Impact Factor
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    ABSTRACT: A greater understanding of the epidemiology, pathogenesis, and pathophysiology of pulmonary artery hypertension (PAH) has led to significant advances, but the disease remains fatal. Treatment options are neither universally available nor always effective, underscoring the need for development of novel therapies and therapeutic strategies. Clinical trials to date have provided evidence of efficacy, but were limited in evaluating the scope and duration of treatment effects. Numerous potential targets in varied stages of drug development exist, in addition to novel uses of familiar therapies. The pursuit of gene and cell-based therapy continues, and device use to help acute deterioration and chronic management is emerging. This rapid surge of drug development has led to multicenter pivotal clinical trials and has resulted in novel ethical and global clinical trial concerns. This paper will provide an overview of the opportunities and challenges that await the development of novel treatments for PAH.
    Journal of the American College of Cardiology 12/2013; 62(25 Suppl):D82-91. · 15.34 Impact Factor
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    ABSTRACT: Pulmonary hypertension (PH) is a rare disease in newborns, infants, and children that is associated with significant morbidity and mortality. In the majority of pediatric patients, PH is idiopathic or associated with congenital heart disease and rarely is associated with other conditions such as connective tissue or thromboembolic disease. Incidence data from the Netherlands has revealed an annual incidence and point prevalence of 0.7 and 4.4 for idiopathic pulmonary arterial hypertension and 2.2 and 15.6 for pulmonary arterial hypertension, respectively, associated with congenital heart disease (CHD) cases per million children. The updated Nice classification for PH has been enhanced to include a greater depth of CHD and emphasizes persistent PH of the newborn and developmental lung diseases, such as bronchopulmonary dysplasia and congenital diaphragmatic hernia. The management of pediatric PH remains challenging because treatment decisions continue to depend largely on results from evidence-based adult studies and the clinical experience of pediatric experts.
    Journal of the American College of Cardiology 12/2013; 62(25 Suppl):D117-26. · 15.34 Impact Factor
  • Katherine Odem-Davis, Thomas R Fleming
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    ABSTRACT: Evaluation of non-inferiority is based on ruling out a threshold for what would constitute unacceptable loss of efficacy of an experimental treatment relative to an active comparator "Standard". This threshold, the "non-inferiority margin", is often based on preservation of a percentage of Standard's effect. To obtain an estimate of this effect to be used in the development of the "non-inferiority margin", data are needed from earlier trials comparing Standard to placebo if the non-inferiority trial does not have a placebo arm. This approach often provides a biased over-estimate of Standard's true effect in the setting of the current non-inferiority study. We describe two commonly used non-inferiority margin methods that adjust for this bias, the two-confidence interval (95-95) and the Synthesis margins. However, the added 'variance inflation' adjustment made by 95-95 margin diminishes with increasing information from historical trial(s), and the Synthesis margin is based on a strong assumption that the relative bias is known. We introduce an alternative "Bias-adjusted" margin addressing vulnerabilities of each by attenuating the estimate and by accounting for uncertainty in the true level of bias. Examples and asymptotic estimates of non-inferiority hypothesis rejection rates in the proportional hazards setting are used to compare methods.
    Statistics in Biopharmaceutical Research 08/2013; 5(3). · 0.70 Impact Factor
  • John H Powers, Thomas R Fleming
    Clinical investigation. 03/2013; 3(3):215-218.
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    ABSTRACT: The HIV Prevention Trial Network (HPTN) 052 Study is a Phase III, two-arm, controlled, open-labeled, randomized clinical trial designed to determine whether early antiretroviral therapy (ART) can prevent the sexual transmission of human immunodeficiency virus type 1 (HIV-1). A total of 1763 couples in which one partner was HIV-1-positive and the other was HIV-1-negative were enrolled in four continents, nine countries and thirteen study sites. The HIV-1-positive partner was randomly assigned to either of the two arms: "immediate" (early) therapy with ART initiated upon enrollment plus HIV primary care, or "delayed" therapy with HIV primary care but ART initiated when the index case would have two consecutive measurements of a CD4+ cell count within or below the range of 200-250cells/mm(3), or develop an AIDS-defining illness. In this paper, we describe several key statistical considerations for the design of this landmark study. Despite that the observed event rates were lower than expected, which might have compromised the study power, an early release of the trial results in May 2011 showed an overwhelming 96% risk reduction for the immediate therapy in the prevention of genetically linked HIV-1 incident transmissions. Nevertheless, the durability of its long-term effectiveness is yet to be assessed. The HPTN 052 Study is still ongoing and will not complete till 2015.
    Contemporary clinical trials 07/2012; 33(6):1280-6. · 1.51 Impact Factor
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    ABSTRACT: Efficacy endpoints for previous registrational trials of antimicrobials for acute bacterial skin and skin structure infections (ABSSSIs) and community-acquired bacterial pneumonia (CABP) were based on nonstandardized, clinician-based observations and decisions, as well as on patient reports. More quantifiable, reproducible, and externally verifiable endpoints could improve the design of future noninferiority trials. At the request of the Food and Drug Administration, the Foundation for the National Institutes of Health convened a broadly representative scientific project team to evaluate potential endpoints for such registrational trials. Review of historical and modern data led to the conclusion that antimicrobial treatment effects are most apparent early in therapy; later outcomes provide important supportive information. Although evidence is incomplete, early response endpoints can anchor noninferiority hypotheses in ABSSSI and CABP registrational trials, thereby allowing evidence-based drug development to continue. Further research is underway to establish which short- and long-term outcomes are well-defined, reliable, and reflective of how patients feel, function, or survive.
    Clinical Infectious Diseases 06/2012; 55(8):1114-1121. · 9.42 Impact Factor
  • Thomas R Fleming, John H Powers
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    ABSTRACT: One of the most important considerations in designing clinical trials is the choice of outcome measures. These outcome measures could be clinically meaningful endpoints that are direct measures of how patients feel, function, and survive. Alternatively, indirect measures, such as biomarkers that include physical signs of disease, laboratory measures, and radiological tests, often are considered as replacement endpoints or 'surrogates' for clinically meaningful endpoints. We discuss the definitions of clinically meaningful endpoints and surrogate endpoints, and provide examples from recent clinical trials. We provide insight into why indirect measures such as biomarkers may fail to provide reliable evidence about the benefit-to-risk profile of interventions. We also discuss the nature of evidence that is important in assessing whether treatment effects on a biomarker reliably predict effects on a clinically meaningful endpoint, and provide insights into why this reliability is specific to the context of use of the biomarker. Copyright © 2012 John Wiley & Sons, Ltd.
    Statistics in Medicine 06/2012; 31(25):2973-84. · 2.04 Impact Factor
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    ABSTRACT: Definitive evidence of clinical efficacy in a Phase 3 trial is best shown by a beneficial impact on a clinically meaningful endpoint-that is, an endpoint that directly measures how a patient feels (symptoms), functions (the ability to perform activities in daily life), or survives. In idiopathic pulmonary fibrosis (IPF), we believe the endpoints that best meet these criteria are all-cause mortality and all-cause nonelective hospitalization. There are no validated measures of symptoms or broader constructs such as health status or functional status in IPF. A surrogate endpoint is defined as an indirect measure that is intended to substitute for a clinically meaningful endpoint. Surrogate endpoints can be appropriate outcome measures if validated. However, validation requires substantial evidence that the effect of an intervention on a clinically meaningful endpoint is reliably predicted by the effect of an intervention on the surrogate endpoint. For patients with IPF, there are currently no validated surrogate endpoints.
    American Journal of Respiratory and Critical Care Medicine 04/2012; 185(10):1044-8. · 11.04 Impact Factor
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    Mark D Rothmann, Jenny J Zhang, Laura Lu, Thomas R Fleming
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    ABSTRACT: In many settings, testing has been proposed to assess the effect of an experimental regimen within a biomarker-positive subgroup where it is biologically plausible that benefit is stronger in such patients, and in the overall population that also includes biomarker-negative subjects less likely to benefit from that regimen. A statistically favorable result in the biomarker-positive subgroup would lead to a claim for that subgroup, whereas a statistically favorable result for the overall population would lead to a claim that includes both biomarker subgroups. The latter setting is problematic when biomarker-negative patients truly do not benefit from the experimental regimen. When it is prespecified that biomarker-negative patients should not be included in the primary analysis of treatment effect in biomarker-positive patients because of the likelihood that treatment effects would differ between the 2 subgroups, it is logically inconsistent to include biomarker-positive patients in the primary analysis of treatment effect in biomarker-negative patients.
    Drug information journal 03/2012; 46(2):175-179. · 0.49 Impact Factor
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    ABSTRACT: One of the most important considerations in designing clinical trials is the choice of outcome measures. These outcome measures could be clinically meaningful endpoints that are direct measures of how patients feel, function, and survive. Alternatively, indirect measures, such as biomarkers that include physical signs of disease, laboratory measures, and radiological tests, often are considered as replacement endpoints or ‘surrogates’ for clinically meaningful endpoints. We discuss the definitions of clinically meaningful endpoints and surrogate endpoints, and provide examples from recent clinical trials. We provide insight into why indirect measures such as biomarkers may fail to provide reliable evidence about the benefit‐to‐risk profile of interventions. We also discuss the nature of evidence that is important in assessing whether treatment effects on a biomarker reliably predict effects on a clinically meaningful endpoint, and provide insights into why this reliability is specific to the context of use of the biomarker. Copyright © 2012 John Wiley & Sons, Ltd.
    Statistics in Medicine 01/2012; 31(25). · 2.04 Impact Factor
  • Thomas R Fleming, Scott S Emerson
    New England Journal of Medicine 10/2011; 365(17):1557-9. · 54.42 Impact Factor
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    ABSTRACT: Antiretroviral therapy that reduces viral replication could limit the transmission of human immunodeficiency virus type 1 (HIV-1) in serodiscordant couples. In nine countries, we enrolled 1763 couples in which one partner was HIV-1-positive and the other was HIV-1-negative; 54% of the subjects were from Africa, and 50% of infected partners were men. HIV-1-infected subjects with CD4 counts between 350 and 550 cells per cubic millimeter were randomly assigned in a 1:1 ratio to receive antiretroviral therapy either immediately (early therapy) or after a decline in the CD4 count or the onset of HIV-1-related symptoms (delayed therapy). The primary prevention end point was linked HIV-1 transmission in HIV-1-negative partners. The primary clinical end point was the earliest occurrence of pulmonary tuberculosis, severe bacterial infection, a World Health Organization stage 4 event, or death. As of February 21, 2011, a total of 39 HIV-1 transmissions were observed (incidence rate, 1.2 per 100 person-years; 95% confidence interval [CI], 0.9 to 1.7); of these, 28 were virologically linked to the infected partner (incidence rate, 0.9 per 100 person-years, 95% CI, 0.6 to 1.3). Of the 28 linked transmissions, only 1 occurred in the early-therapy group (hazard ratio, 0.04; 95% CI, 0.01 to 0.27; P<0.001). Subjects receiving early therapy had fewer treatment end points (hazard ratio, 0.59; 95% CI, 0.40 to 0.88; P=0.01). The early initiation of antiretroviral therapy reduced rates of sexual transmission of HIV-1 and clinical events, indicating both personal and public health benefits from such therapy. (Funded by the National Institute of Allergy and Infectious Diseases and others; HPTN 052 ClinicalTrials.gov number, NCT00074581.).
    New England Journal of Medicine 08/2011; 365(6):493-505. · 54.42 Impact Factor
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    ABSTRACT: Suppose a standard therapy (Standard) has been established to provide a clinically important reduction in risk of irreversible morbidity or mortality. In that setting, the safety and efficacy of an experimental intervention likely would be assessed in a clinical trial providing a comparison with Standard rather than a placebo arm. Such a trial often is designed to assess whether the efficacy of the experimental intervention is not unacceptably worse than that of Standard, and is called a non-inferiority trial. Formally, the non-inferiority trial usually is designed to rule out a non-inferiority margin, defined as the minimum threshold for what would constitute an unacceptable loss of efficacy. Even though the literature has many important articles identifying various approaches to the design and conduct of non-inferiority trials, confusion remains especially regarding key considerations for selecting the non-inferiority margin. The purpose of this article is to provide improved clarity regarding these considerations. We present scientific insights into many factors that should be addressed in the design and conduct of non-inferiority trials to enhance their integrity and reliability, and provide motivation for key considerations that guide the selection of non-inferiority margins. We also provide illustrations and insights from recent experiences. Two considerations are essential, and should be addressed in separate steps, in the formulation of the non-inferiority margin. First, the margin should be formulated using adjustments to account for bias or lack of reliability in the estimate of the effect of Standard in the non-inferiority trial setting. Second, the non-inferiority margin should be formulated to achieve preservation of an appropriate percentage of the effect of Standard. The considerations, in particular regarding the importance of preservation of effect, might not apply to settings where it would be ethical as well as clinically relevant to include both Standard and placebo arms in the trial for direct comparisons with the experimental intervention arm. Non-inferiority trials with non-rigorous margins allow substantial risk for accepting inadequately effective experimental regimens, leading to the risk of erosion in quality of health care. The design and conduct of non-inferiority trials, including selection of non-inferiority margins, should account for many factors that can induce bias in the estimated effect of Standard in the non-inferiority trial and thus lead to bias in the estimated effect of the experimental treatment, for the need to ensure the experimental treatment preserves a clinically acceptable fraction of Standard's effect, and for the particular vulnerability of the integrity of a non-inferiority trial to the irregularities in trial conduct. Due to the inherent uncertainties in non-inferiority trials, alternative designs should be pursued whenever possible.
    Clinical Trials 08/2011; 8(4):432-9. · 1.94 Impact Factor
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    ABSTRACT: BACKGROUND: Antiretroviral therapy that reduces viral replication could limit the transmission of human immunodeficiency virus type 1 (HIV-1) in serodiscordant couples. METHODS: In nine countries, we enrolled 1763 couples in which one partner was HIV-1-positive and the other was HIV-1-negative; 54% of the subjects were from Africa, and 50% of infected partners were men. HIV-1-infected subjects with CD4 counts between 350 and 550 cells per cubic millimeter were randomly assigned in a 1:1 ratio to receive antiretroviral therapy either immediately (early therapy) or after a decline in the CD4 count or the onset of HIV-1-related symptoms (delayed therapy). The primary prevention end point was linked HIV-1 transmission in HIV-1-negative partners. The primary clinical end point was the earliest occurrence of pulmonary tuberculosis, severe bacterial infection, a World Health Organization stage 4 event, or death. RESULTS: As of February 21, 2011, a total of 39 HIV-1 transmissions were observed (incidence rate, 1.2 per 100 person-years; 95% confidence interval [CI], 0.9 to 1.7); of these, 28 were virologically linked to the infected partner (incidence rate, 0.9 per 100 person-years, 95% CI, 0.6 to 1.3). Of the 28 linked transmissions, only 1 occurred in the early-therapy group (hazard ratio, 0.04; 95% CI, 0.01 to 0.27; P<0.001). Subjects receiving early therapy had fewer treatment end points (hazard ratio, 0.59; 95% CI, 0.40 to 0.88; P=0.01). CONCLUSIONS: The early initiation of antiretroviral therapy reduced rates of sexual transmission of HIV-1 and clinical events, indicating both personal and public health benefits from such therapy. (Funded by the National Institute of Allergy and Infectious Diseases and others; HPTN 052 ClinicalTrials.gov number, NCT00074581.). Comment in [In Process Citation]. [Rev Clin Esp. 2012] ACP Journal Club. Early antiretroviral therapy reduced HIV-1 transmission in serodiscordant couples. [Ann Intern Med. 2011] Prevention of HIV-1 infection with antiretroviral therapy. [N Engl J Med. 2011] Antiretroviral treatment as prevention. [N Engl J Med. 2011] Does early initiation of antiretroviral therapy prevent HIV transmission in serodiscordant couples? [Natl Med J India. 2012] Antiretroviral combination therapy markedly reduces risk of heterosexual HIV-1 transmission. [Evid Based Med. 2012] Prevention of HIV-1 infection with antiretroviral therapy. [N Engl J Med. 2011]
    08/2011;
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    ABSTRACT: Background—Antiretroviral therapy that reduces viral replication could limit the transmission of human immunodeficiency virus type 1 (HIV-1) in serodiscordant couples.
    New England Journal of Medicine 08/2011; 365(6):493-505. · 54.42 Impact Factor
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    ABSTRACT: The long-term safety and tolerability of sildenafil treatment of pulmonary arterial hypertension (PAH) were assessed. Two hundred fifty-nine of 277 randomized and treated patients completed a 12-week, double-blind, placebo-controlled trial (SUPER-1 [Sildenafil Use in Pulmonary Arterial Hypertension]) of oral sildenafil in treatment-naive patients with PAH (96% functional class II/III) and entered an open-label uncontrolled extension study (SUPER-2) that continued until the last patient completed 3 years of sildenafil treatment. Patients titrated to sildenafil 80 mg tid; one dose reduction for tolerability was allowed during the titration phase. The median duration of sildenafil treatment across SUPER-1 and SUPER-2 was 1,242 days (range, 1-1,523 days); 170 patients (61%) completed both studies, and 89 patients discontinued from SUPER-2. After 3 years, 87% of 183 patients on treatment were receiving sildenafil 80 mg tid. Of patients remaining under follow-up, 3%, 10%, and 18% were receiving a second approved PAH therapy at 1, 2, and 3 years, respectively. At 3 years post-SUPER-1 baseline, 127 patients had an increased 6-min walk distance (6MWD); 81 improved and 86 maintained functional class. Most adverse events were of mild or moderate severity. At 3 years, 53 patients had died (censored, n = 37). Three-year estimated survival rate was 79%; if all censored patients were assumed to have died, 3-year survival rate was 68%. No deaths were considered to be treatment related. Long-term treatment of PAH initiated as sildenafil monotherapy was generally well tolerated. After 3 years, the majority of patients (60%) who entered the SUPER-1 trial improved or maintained their functional status, and 46% maintained or improved 6MWD.
    Chest 05/2011; 140(5):1274-83. · 7.13 Impact Factor
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    ABSTRACT: Recurrent events are common in medical research for subjects who are followed for the duration of a study. For example, cardiovascular patients with an implantable cardioverter defibrillator (ICD) experience recurrent arrhythmic events that are terminated by shocks or antitachycardia pacing delivered by the device. In a published randomized clinical trial, a recurrent-event model was used to study the effect of a drug therapy in subjects with ICDs, who were experiencing recurrent symptomatic arrhythmic events. Under this model, one expects the robust variance for the estimated treatment effect to diminish when the duration of the trial is extended, due to the additional events observed. However, as shown in this article, that is not always the case. We investigate this phenomenon using large datasets from this arrhythmia trial and from a diabetes study, with some analytical results, as well as through simulations. Some insights are also provided on existing sample size formulae using our results.
    Biometrics 03/2011; 67(4):1564-72. · 1.52 Impact Factor
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    Thomas R Fleming
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    ABSTRACT: The reliability and interpretability of results from clinical trials can be substantially reduced by missing data. Frequently used approaches to address these concerns, such as upward adjustments in sample sizes or simplistic methods for handling missing data, including last-observation-carried-forward, complete-case, or worst-case analyses, are usually inadequate. Although rational imputation methods may be useful to treat missingness after it has occurred, these methods depend on untestable assumptions. Thus, the preferred and often only satisfactory approach to addressing missing data is to prevent it. Procedures should be in place to maximize the likelihood that outcome data will be obtained at scheduled times of evaluation for all surviving patients who have not withdrawn consent. To meaningfully reduce missing data, it is important to recognize and address many factors that commonly lead to higher levels of missingness.
    Annals of internal medicine 01/2011; 154(2):113-7. · 16.10 Impact Factor

Publication Stats

3k Citations
578.52 Total Impact Points

Institutions

  • 1993–2014
    • University of Washington Seattle
      • Department of Biostatistics
      Seattle, Washington, United States
  • 2010–2013
    • Fred Hutchinson Cancer Research Center
      • • Statistical Center for HIV/AIDS Research and Prevention
      • • Division of Vaccine and Infectious Disease
      Seattle, Washington, United States
  • 2006–2012
    • U.S. Food and Drug Administration
      • Office of Biostatistics
      Washington, D. C., DC, United States
  • 2011
    • University of North Carolina at Chapel Hill
      • Institute for Global Health and Infectious Diseases
      North Carolina, United States
  • 2009
    • National Institute of Allergy and Infectious Diseases
      Maryland, United States
  • 2004
    • Baylor College of Medicine
      • Winters Center for Heart Failure Research
      Houston, TX, United States
  • 2003
    • Nottingham Trent University
      Nottigham, England, United Kingdom
  • 1997–1999
    • University of Texas MD Anderson Cancer Center
      • Department of Biomathematics
      Houston, TX, United States