Biomedical subjects

Jason J Z Liao

Publications and source records attributed to Jason J Z Liao.

4 recordsLinked to original sources

PubMed2006

Assessing the reproducibility of an analytical method.

The reproducibility of a validated analytical method may require reassessment because of various reasons, such as the transfer between laboratories or companies, changes in the instruments or software platforms (or both), or changes in critical reagents, among others. This paper is a demonstration of an assay bridging study in evaluating reproducibility. The approach is simple but very informative and offers many advantages over existing approaches.

Bias↗

PubMed2005

Comparing the concentration curves directly in a pharmacokinetics, bioavailability/bioequivalence study.

In a traditional pharmacokinetics (PK), bioavailability (BA) /bioequivalence (BE) study, the same number of time points and sampling times are used for each subject. Often, an indirect inference is then made on some PK parameters such as area under the plasma concentration curve (AUC), maximum plasma concentration (C(max)), time to maximum plasma concentration (T(max)) or half-life. However, since these PK parameters are summarized from repeated measurements, a lot of information can be lost. The indirect inferences on some PK parameters are not always accurate. Taking the repeated measurements of the concentration curve into consideration, a functional linear model has been developed to compare concentration curves directly instead of the PK parameters. Considering the nature of repeated measurements, a multiple testing procedure is proposed to assess the equality of two concentration curves. A real data set is used to demonstrate the proposed procedure.

Antihypertensive Agents↗

PubMed2005

A linear mixed-effects calibration in qualifying experiments.

In many applications, controls are used to monitor the process or experiment and to assess whether the process is in control or the experiment is valid. In this case, the traditional fixed-effects calibration is usually not adequate, but a mixed-effects model is appropriate. In this article, a linear mixed-effects calibration model is considered to qualify an experiment. Two estimating methods for the controls based on maximum likelihood and restricted maximum likelihood are proposed. The bias and mean squared error performances are studied by simulation. Five different methods to construct confidence intervals for the controls are compared. A dataset is used to demonstrate the advantages of the mixed-effects model.

Calibration↗

PubMed2005

Agreement for curved data.

An agreement problem usually involves assessing the concordance of two sets of measurements, and the problem covers a broad range of data. In practice, the observations are often curves instead of the traditional points. In this article, the agreement problem is studied for curved data. Following the rationale in constructing a correlation coefficient curve for heterocorrelaticity, an agreement curve is proposed to measure agreement as a function of the independent variable for curved data. The agreement curve overcomes the drawback when only one index is used in assessing the agreement of two measurements, and it covers all situations including the nonconstant mean, nonhomogenous variance, and the data range. A real dataset is used to demonstrate the approach and to show accurate assessment and information gained if curved data are used.

Algorithms↗