Shein-Chung Chow

Journal article Stat Med · April 15, 2006 Featured Publication The problem of selecting a non-inferiority margin and the corresponding statistical test for non-inferiority in active control trials is considered. For selection of non-inferiority margin, the guideline by the International Conference on Harmonization (IC ... Full text Link to item Cite

Statistical inference for cancer trials with treatment switching.

Journal article Stat Med · June 30, 2005 Featured Publication In cancer clinical trials, it is not uncommon that some patients switched their treatments due to lack of efficacy and/or disease progression under ethical consideration. This treatment switch makes it difficult for the evaluation of the efficacy of the tr ... Full text Link to item Cite

Statistical consideration of adaptive methods in clinical development.

Journal article J Biopharm Stat · 2005 Featured Publication In recent years, the use of adaptive methods in clinical development based on accrued data has become very popular due to its flexibility in modifying trial procedures and/or statistical procedures of on-going clinical trials. However, it is a concern that ... Full text Link to item Cite

Inference for clinical trials with some protocol amendments.

Journal article J Biopharm Stat · 2005 Featured Publication The use of adaptive methods in clinical development has become very popular in recent years due to its flexibility in modifying trial procedures and/or statistical procedures of on-going clinical trials. Modifications to trial procedures are usually docume ... Full text Link to item Cite

A hybrid Bayesian adaptive design for dose response trials.

Journal article J Biopharm Stat · 2005 Featured Publication In recent years, the use of adaptive design methods based on accrued data of on-going trials have become very popular for dose response trials in early clinical development due to their flexibility (EMEA, 2002). In this paper, we developed a hybrid frequen ... Full text Link to item Cite

A Bayesian approach on sample size calculation for comparing means.

Journal article J Biopharm Stat · 2005 Featured Publication In clinical research, parameters required for sample size calculation are usually unknown. A typical approach is to use estimates from some pilot studies as the true parameters in the calculation. This approach, however, does not take into consideration sa ... Full text Link to item Cite

Assessing bioequivalence using genomic data.

Journal article J Biopharm Stat · November 2004 Featured Publication For approval of a generic drug product, the assessment of bioequivalence in drug absorption is usually considered as a surrogate for evaluation of drug efficacy and safety in clinical studies. For some drug products, the United States Food and Drug Adminis ... Full text Link to item Cite

Cross-validation for linear model with unequal variances in genomic analysis.

Journal article J Biopharm Stat · August 2004 Featured Publication In recent years, genomic studies are usually conducted to identify genes that may have an impact on clinical outcomes. The identified genes are then used to establish a predictive model for identifying subjects who are most likely to respond to the test tr ... Full text Link to item Cite

Analysis of clinical data with breached blindness.

Journal article Stat Med · April 30, 2004 Featured Publication In clinical trials, blinding is usually employed to prevent bias that may be introduced due to the knowledge of the identity of the treatment codes. This bias could alter the conclusion of statistical inference on the treatment effect. The purpose of this ... Full text Link to item Cite

Sample size determination based on rank tests in clinical trials.

Journal article J Biopharm Stat · November 2003 Featured Publication The problem of sample size determination based on three commonly used non-parametric rank based tests, namely, one-sample Wilcoxon's rank sum test, two-sample's Wilcoxon's rank sum test, and the rank-based test for independence is studied. Explicit formula ... Full text Link to item Cite

Stability analysis with discrete responses.

Journal article J Biopharm Stat · August 2003 Featured Publication We consider the estimation of shelf life of a drug product when the stability data are discrete. When there is no batch-to-batch variation, the proposed shelf life estimator is an approximate 95% lower confidence bound of the true shelf life. In the presen ... Full text Link to item Cite

Examining outlying subjects and outlying records in bioequivalence trials.

Journal article J Biopharm Stat · February 2003 Featured Publication The problem of detecting outliers in bioequivalence trials is considered. We formulate the problem as a hypothesis-testing problem under a mean-shift model and propose a test procedure based on the likelihood function. The test statistic has two components ... Full text Link to item Cite

In vitro bioequivalence testing.

Journal article Stat Med · January 15, 2003 Featured Publication A statistical test is proposed for in vitro bioequivalence testing between drug products such as nasal aerosols and nasal sprays. The proposed test generalizes the one recommended in the FDA 1999 guidance to the situation where replicated observations obta ... Full text Link to item Cite

On sample size calculation based on odds ratio in clinical trials.

Journal article J Biopharm Stat · November 2002 Featured Publication Sample size calculation formulas for testing equality, noninferiority, superiority, and equivalence based on odds ratio were derived under both parallel and one-arm crossover designs. An example concerning the study of odds ratio between a test compound (t ... Full text Link to item Cite

Tests for inter-subject and total variabilities under crossover designs.

Journal article J Biopharm Stat · November 2002 Featured Publication In this paper, we consider statistical tests for inter-subject and total variabilities between treatments under crossover designs. Since estimators of variance components for inter-subject variability and total variability in crossover design are not indep ... Full text Link to item Cite

A note on sample size calculation for mean comparisons based on noncentral t-statistics.

Journal article J Biopharm Stat · November 2002 Featured Publication One-sample and two-sample t-tests are commonly used in analyzing data from clinical trials in comparing mean responses from two drug products. During the planning stage of a clinical study, a crucial step is the sample size calculation, i.e., the determina ... Full text Link to item Cite

A practical approach for comparing means of two groups without equal variance assumption.

Journal article Stat Med · October 30, 2002 Featured Publication In this paper we consider two-groups of i.i.d. normally distributed random variables (N(mu(x),sigma(x) (2)) and N(mu(y),sigma(y) (2))) without assuming equal variance (sigma(x) (2) = sigma(y) (2)). We propose a simple method for constructing confidence bou ... Full text Link to item Cite

A note on statistical methods for assessing therapeutic equivalence.

Journal article Control Clin Trials · October 2002 Featured Publication The two one-sided tests procedure and the confidence interval approach are two commonly used statistical approaches for testing therapeutic equivalence or assessing bioequivalence. However, some confusion arises. For example, what is the difference between ... Full text Link to item Cite

Bridging studies in clinical development.

Journal article J Biopharm Stat · August 2002 Featured Publication Global development of pharmaceutical products has become the key to the success of any pharmaceutical sponsors. It is therefore crucial to address the efficacy and safety variations of a new test pharmaceutical product among different geographic regions du ... Full text Link to item Cite

On the assessment of similarity for dissolution profiles of two drug products.

Journal article J Biopharm Stat · August 2002 Featured Publication The assessment of similarity between dissolution profiles of two drug products is considered. After reviewing some existing approaches, we propose a statistical method of assessing local and global similarities based on a time series model for the ratio of ... Full text Link to item Cite

Assessing sensitivity and similarity in bridging studies.

Journal article J Biopharm Stat · August 2002 Featured Publication In pharmaceutical industry, the sponsors are interested in bringing their drug products from one region (e.g., the United States of America) to another region (e.g., Asian Pacific) to increase the exclusivity of the drug products in the marketplace. Howeve ... Full text Link to item Cite

On statistical power for average bioequivalence testing under replicated crossover designs.

Journal article J Biopharm Stat · August 2002 Featured Publication In its recent guidance on bioequivalence, the U.S. Food and Drug Administration (FDA) recommends a two-sequence, four-period (2 x 4) replicated crossover design be used for assessment of population and individual bioequivalence [FDA. Guidance for Industry ... Full text Link to item Cite

Reproducibility probability in clinical trials.

Journal article Stat Med · June 30, 2002 Featured Publication For marketing approval of a new drug product, the United States Food and Drug Administration (FDA) requires that substantial evidence of the effectiveness of the drug product be provided through the conduct of at least two adequate and well-controlled clin ... Full text Link to item Cite

Individual bioequivalence testing under 2x3 designs.

Journal article Stat Med · March 15, 2002 Featured Publication In recent years, as more generic drug products become available, it is a concern not only whether generic drug products that have been approved based on the regulation of average bioequivalence will have the same quality, safety and efficacy as that of the ... Full text Link to item Cite

Probability lower bounds for USP/NF tests.

Journal article J Biopharm Stat · February 2002 Featured Publication In the pharmaceutical industry, a number of tests such as content uniformity and dissolution testing are usually performed at various stages of drug manufacturing process to ensure that the drug product meets standards for identity, strength, quality, puri ... Full text Link to item Cite

Two-phase shelf-life estimation.

Journal article Stat Med · April 30, 2001 Featured Publication Unlike most drug products, some drug products must be stored at several temperatures, such as -20 degrees C, 5 degrees C and 25 degrees C, in order to maintain the stability of the drug products. Drug products of this kind are usually referred to as frozen ... Full text Link to item Cite

On sample size calculation in bioequivalence trials.

Journal article J Pharmacokinet Pharmacodyn · April 2001 Featured Publication Sample size calculation plays an important role in bioequivalence trials. In practice, a bioequivalence study is usually conducted under a crossover design or a parallel design with raw data or log-transformed data. In this paper, we discuss the difference ... Full text Link to item Cite

The bootstrap procedure in individual bioequivalence.

Journal article Stat Med · October 30, 2000 Featured Publication A bootstrap-type hypothesis test procedure for assessing individual (or population) bioequivalence between two drug formulations is suggested in a draft guidance from the United States Food and Drug Administration (FDA). The purpose of this article is to s ... Full text Link to item Cite

On statistical analysis for placebo-challenging designs in clinical trials.

Journal article Stat Med · April 30, 2000 Featured Publication In clinical trials, appropriate designs are often chosen to address scientific/medical questions of particular interest to the investigator. For a chosen statistical design, however, standard statistical procedures may not be applicable owing to the nature ... Full text Link to item Cite