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V DeGruttola

Publications and source records attributed to V DeGruttola.

24 records · Page 2Linked to original sources
PubMed1995

Evaluating surrogate markers.

We discuss approaches for efficiently evaluating potential surrogate markers; in particular, we focus on case-cohort designs in which marker evaluation is undertaken only for a random sample of subjects within a randomized trial and for all other subjects who develop a major clinical outcome. These designs will be useful in clinical trials in which a highly significant treatment difference on clinical outcome has been obtained. In addition, we describe a method for using data from all available studies using a meta-analysis to explore the association of treatment effects on the potential marker and on clinical outcome. This may be the most effective approach for marker evaluation because it uses data from both large and small trials and incorporates information from trials in which nonsignificant treatment differences on the major clinical outcome are obtained.

Biomarkers↗
PubMed1994

Serum p24 antigen level as an intermediate end point in clinical trials of zidovudine in people infected with human immunodeficiency virus type 1. Aids Clinical Trials Group Virology Laboratories.

Serum p24 antigen levels were examined in subjects from three clinical trials of zidovudine to determine whether the pattern of change in serum p24 antigen during the first 8-16 weeks of therapy was associated with human immunodeficiency virus type 1 (HIV-1) disease progression or death. Among 406 patients with AIDS and a first episode of Pneumocystis carinii pneumonia, 65% had measurable pretreatment concentrations of serum p24 antigen (> or = 10 pg/mL). Changes during treatment were not associated with reduced mortality. In 637 mildly symptomatic patients, 24% had measurable concentrations, and changes were marginally associated with increased time until more advanced disease. Among 683 asymptomatic patients, 18% had measurable concentrations, and changes were not associated with increased time until progression. Despite the small number of clinical events and the low rate of serum p24 antigen positivity in the latter two studies, pretreatment serum p24 antigen levels were predictive of clinical outcome; subsequent measurements appear to be of limited use in evaluating zidovudine therapy.

AIDS-Related Complex↗
PubMed1989

Infectiousness of HIV between male homosexual partners.

To estimate the risk of transmission of HIV per receptive anal sexual contact, 329 homosexually-active men, representing 155 sexual partnerships, were enrolled into a study. Information on HIV infection status and sexual behavior within and outside the primary relationship was collected. Of these 329 men, 24 had AIDS and 31 had ARC. Of the 155 couples, 35 consisted of partners that were both HIV +; 62 of partners that were both HIV-; and 58 were discordant. A binomial model was fit to data obtained in the first visit to estimate per contact risk of HIV transmission. Assuming a constant risk of transmission per sexual contact between infected and uninfected partners, the estimated risk is about 5 to 30 per 1000 receptive anal exposures to ejaculate. Although the average risk of HIV transmission per sexual contact appears to be low, there appears to be great variability in infectivity. To model this variability over time and across individuals, more complex models must be fit to longitudinal studies of sexual partners.

AIDS-Related Complex↗
PubMedDate not supplied

Models for empirical Bayes estimators of longitudinal CD4 counts.

In this paper we consider the choice of model used in estimation of trajectories of CD4 T-cell counts by empirical Bayes estimators. Tsiatis et al. have demonstrated that empirical Bayes estimates of CD4 values correct for the bias resulting from measurement error when using CD4 as a covariate in a Cox model to predict clinical events. Here, empirical Bayes estimates from a random effects model are compared to estimates from the more general stochastic regression model presented in Taylor et al. Empirical Bayes estimators based on the two models are judged according to their ability to provide parameter estimates in a Cox model predicting clinical outcomes. Data from ACTG 118 are used as an illustration.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Surrogate endpoints.

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Anti-HIV Agents↗