BORDEN, EC, KIM, K, RYAN, L, BLUM, RH, SHIRAKI, M, TORMEY, DC, COMIS, RL, HAHN, RG & PARKINSON, DR 1992, 'PHASE-II TRIALS OF INTERFERON-ALPHA AND INTERFERON-BETA IN ADVANCED SARCOMAS', JOURNAL OF INTERFERON RESEARCH, vol. 12, no. 6, pp. 455-458.
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CATALANO, PJ & RYAN, LM 1992, 'BIVARIATE LATENT VARIABLE MODELS FOR CLUSTERED DISCRETE AND CONTINUOUS OUTCOMES', JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION, vol. 87, no. 419, pp. 651-658.
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We use the concept of a latent variable to derive the joint distribution of a continuous and a discrete outcome, and then extend the model to allow for clustered data. The model Can be parameterized in a way that allows one to write the joint distribution as a product of a standard random effects model for the continuous variable and a correlated probit model for the discrete variable. This factorization suggests a convenient approach to parameter estimation using quasi-likelihood techniques. Our approach is motivated by the analysis of developmental toxicity experiments for which a number of discrete and continuous outcomes are measured on offspring clustered within litters. Fetal weight and malformation data illustrate the results.
Catalano, PJ & Ryan, LM 1992, 'Bivariate latent variable models for clustered discrete and continuous outcomes', Journal of the American Statistical Association, vol. 87, no. 419, pp. 651-658.
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We use the concept of a latent variable to derive the joint distribution of a continuous and a discrete outcome, and then extend the model to allow for clustered data. The model can be parameterized in a way that allows one to write the joint distribution as a product of a standard random effects model for the continuous variable and a correlated probit model for the discrete variable. This factorization suggests a convenient approach to parameter estimation using quasi-likelihood techniques. Our approach is motivated by the analysis of developmental toxicity experiments for which a number of discrete and continuous outcomes are measured on offspring clustered within litters. Fetal weight and malformation data illustrate the results. © 1992 Taylor & Francis Group, LLC.
Catalano, PJ & Ryan, LM 1992, 'Bivariate Latent Variable Models for Clustered Discrete and Continuous Outcomes', Journal of the American Statistical Association, vol. 87, no. 419, pp. 651-651.
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DAGOSTINO, RB, LANGE, N & RYAN, L 1992, 'PAPERS FROM THE SYMPOSIUM ON LONGITUDINAL DATA-ANALYSIS, 19-21 JUNE 1991 - OVERVIEW', STATISTICS IN MEDICINE, vol. 11, no. 14-15, pp. 1801-1805.
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D'agostino, RB, Lange, N & Ryan, L 1992, 'Overview', Statistics in Medicine, vol. 11, no. 14-15, pp. 1801-1805.
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D'agostino, RB, Lange, N & Ryan, L 1992, 'The Symposium on Longitudinal Data Analysis. Fort Lauderdale, Florida, 19-21 June 1991.', Stat Med, vol. 11, no. 14-15, pp. 1801-2040.
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FALKSON, G, RYAN, LM & HALLER, DG 1992, 'PHASE-II TRIAL FOR THE EVALUATION OF TRIMETREXATE IN PATIENTS WITH INOPERABLE SQUAMOUS CARCINOMA OF THE ESOPHAGUS', AMERICAN JOURNAL OF CLINICAL ONCOLOGY-CANCER CLINICAL TRIALS, vol. 15, no. 5, pp. 433-435.
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EST 2287 was a Phase II clinical trial conducted by the Eastern Cooperative Oncology Group (ECOG) designed to evaluate trimetrexate in patients with advanced, measurable, inoperable squamous cell carcinoma of the esophagus. The drug was given at a dose o
LEISENRING, W & RYAN, L 1992, 'STATISTICAL PROPERTIES OF THE NOAEL', REGULATORY TOXICOLOGY AND PHARMACOLOGY, vol. 15, no. 2, pp. 161-171.
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The use of the no observed adverse effect level (NOAEL) in setting allowable exposure levels for noncancer endpoints is a source of controversy. Based on computer simulations and empirical studies, several authors have criticized the use of the NOAEL in terms of its sensitivity to sample size and its high sampling variability from experiment to experiment. The purpose of this paper is to derive the statistical distribution of the NOAEL. Using Weibull models, we investigate the impact of the shape of the underlying dose-response curve on the distribution of the NOAEL. The results confirm previous criticisms of the NOAEL and show that average risk levels associated with the NOAEL may be substantial. These results provide additional motivation for developing alternative approaches to risk assessment. © 1992.
RYAN, L 1992, 'QUANTITATIVE RISK ASSESSMENT FOR DEVELOPMENTAL TOXICITY', BIOMETRICS, vol. 48, no. 1, pp. 163-174.
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Pharmaceutical companies and governmental regulatory agencies are becoming increasingly aware of the need for improved statistical methods for developmental toxicity experiments. Although a number of statisticians have become interested in this area, activity has centered mostly on the development of methods to analyze binary outcomes, such as malformations among live pups, while accounting appropriately for the correlation induced by the litter effect. In contrast, the topic of quantitative risk assessment has received relatively little attention. This paper addresses the specific question of how to assess risk appropriately when exposure causes a variety of adverse effects, including resorption and fetal death, in addition to malformations. It will be seen that risk assessments based on a single developmental outcome, such as malformation, may be conservative. A method is proposed for estimating an exposure level at which the overall risk of any adverse effect is acceptably low. The method is based on a continuation ratio formulation of a multinomial distribution, with an additional scale parameter to account for overdispersion. Comparisons are made with binary models on prenatal death and malformation, as well as a binary model that makes no distinction between death and malformation, but simply classifies each fetus as normal or abnormal. Data from several developmental toxicity studies illustrate the results and findings.
Zhang, C 1992, 'Cooperation under uncertainty in distributed expert systems', Artificial Intelligence, vol. 56, no. 1, pp. 21-69.
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