Modeling the durability of ZOSTAVAX® vaccine efficacy in people ≥60 years of age.

Since 2006, the vaccine, ZOSTAVAX(®), has been licensed to prevent herpes zoster. Only limited clinical follow-up data are available to evaluate duration of protection, an important consideration when developing HZ vaccination policy recommendations. Four Poisson regression models were developed based on an integrated analysis of data from the Shingles Prevention Study and its Short Term Persistence extension to estimate the effects of years-since-vaccination and chronological-age on vaccine efficacy among people ≥60 years old.

Factors associated with small abdominal aortic aneurysm expansion rate.

Importance: Because of the high mortality rate after rupture of small abdominal aortic aneurysms (AAAs), surveillance is recommended to detect aneurysm expansion; however, the effects of clinical risk factors on long-term patterns of AAA expansion are poorly characterized.

Objective: To identify significant clinical risk factors associated with the AAA expansion rate for both constant and accelerated expansion trajectories.

Design, Setting, And Participants: A multivariate mixed-effects model was established to identify clinical risk factors associated with the AAA expansion rate.

Establishing a data monitoring committee for clinical trials.

A data monitoring committee (DMC) is a group of clinicians and biostatisticians appointed by study sponsors who provide independent assessment of the safety, scientific validity and integrity of clinical trials. In the United States, the Food and Drug Administration requires the formation of DMC in all trials that assess new interventions. DMC are also strongly recommended in other clinical studies that have substantial safety issues, that have double-blind treatment assignment or that are expected to have a major impact on clinical practice.

Patient satisfaction and use of Veterans Affairs versus non-Veterans Affairs healthcare services by veterans.

Objectives: Chronically ill patients who are not satisfied with their care may change healthcare providers or systems, which could disrupt continuity of care and impede management of their conditions. We examined whether patient satisfaction affected subsequent use of non-Veterans Affairs (VA) services among chronically ill veterans discharged from VA hospitals.

Methods: The data used in this study came from a multicenter trial of increased access to primary care.

Research on informed consent: investigator-developed versus focus group-developed consent documents, a VA cooperative study.

In the Department of Veterans Affairs Cooperative Study (VACSP) #470, A Randomized, Multicenter, Controlled Trial of Multi-Modal Therapy in Veterans with Gulf War Illnesses, a substudy was designed with the primary objective of comparing the utility of an informed consent document developed by a focus group of Gulf War veterans (focus group-developed) to an informed consent document developed by the standard process involving the study investigators (investigator-developed). In December 1998 a focus group of five Gulf War veterans convened at the coordinating center and developed a consent document during three sessions. The focus group used the investigator-developed consent document as a "starting point" and then modified it by consensus agreement.

Potential cost savings of erythropoietin administration in end-stage renal disease.

Background: In a Department of Veterans Affairs randomized controlled trial, a lower dose of recombinant human erythropoietin (epoetin) was shown to attain target hematocrit levels when administered subcutaneously compared with intravenously. Since epoetin is expensive, optimizing the therapeutic effect of epoetin using a strategy that includes subcutaneous administration could lead to substantial cost savings.

Methods: We used an economic cost projection model to estimate potential savings to the Medicare End-Stage Renal Disease Program that could occur during a transition from intravenous to subcutaneous administration of epoetin among hemodialysis patients.

Department of Veterans Affairs Cooperative Studies Program Clinical Trial comparing combined warfarin and aspirin with aspirin alone in survivors of acute myocardial infarction: primary results of the CHAMP study.

Background: Both aspirin and warfarin when used alone are effective in the secondary prevention of vascular events and death after acute myocardial infarction. We tested the hypothesis that aspirin and warfarin therapy, when combined, would be more effective than aspirin monotherapy. Methods and Results- We conducted a randomized open-label study to compare the efficacy of warfarin (target international normalized ratio 1.

Accessing data from external centralized sources to enhance analysis of a completed clinical trial.

After the data collection phase of a clinical trial has been completed, new hypotheses may surface which require additional data before they can be tested. In the Veterans Affairs Cooperative Study on Single Drug Therapy of Hypertension, we investigated the relationship between location of the participating center, race and ability to control blood pressure. The analysis indicated poorer blood pressure control among sites located in the "stroke belt" (southeastern United States), especially among African-Americans.

Improving informed consent in clinical trials: a duty to experiment.

Practitioners of clinical trials have a responsibility to ensure that patients' participation in research be informed and voluntary. This responsibility implies that we should strive continuously to improve the effectiveness of methods for informing prospective research volunteers about experimental studies, thereby enhancing the protection of their interests. We should test innovations in informed consent in realistic contexts (i.

Measuring costs in multisite randomized controlled trials: lessons from the VA Cooperative Studies Program.

Objectives: The interest in the economic impact of new health care interventions has increased dramatically over recent years; however, the results can be highly variable depending upon the economic assumptions made and the approaches taken in collecting the data and in conducting the analyses. This paper describes experiences from the VA Cooperative Studies Program in measuring health care utilization and costs for studies that evaluate clinical interventions.

Methods: Experiences from two multisite randomized clinical trials (RCTs) are highlighted to illustrate strategies used to measure costs by directly measuring health care utilization and economic data within the context of the trials.

Twenty-two-year follow-up in the VA Cooperative Study of Coronary Artery Bypass Surgery for Stable Angina.

We evaluated the 22-year results of initial coronary artery bypass surgery with saphenous vein grafts compared with initial medical therapy on survival, incidence of myocardial infarction, reoperation, and symptomatic status in 686 patients (average age 51) with stable angina in the Veterans Affairs Cooperative Study of Coronary Artery Bypass Surgery. Between 1972 and 1974, 354 patients were assigned to medical treatment and 332 to surgical revascularization. In the surgical cohort, 312 patients underwent operation (operative mortality 5.

Developing and comparing treatment strategies: an annotated portfolio of designs.

Useful clinical strategies are adaptive, specifying the sequence of treatments that are alternatives, what it means for the treatment to "work," the rules for abandoning a treatment, and the subsequent treatments. Because combinatorial complexity precludes comparison of every possible whole strategy, current experiment-based methods rely on comparisons among a few options at particularly crucial decision points, and strategies are pieced together from scraps of information. Nonexperimental methods for strategy development offer a seductive alternative, but their advantages may be illusory.

Statistical evaluation of the role of Helicobacter pylori in stress gastritis: applications of splines and bootstrapping to the logistic model.

Stress gastritis is a serious problem in the intensive care unit population. The recent discovery of the causal nature of Helicobacter pylori (H. pylori) in the development of gastric ulcers led us to examine its relationship with stress gastritis.