Biomedical subjects

Thaddeus Tarpey

Publications and source records attributed to Thaddeus Tarpey.

3 recordsLinked to original sources

PubMed2005

Estimation in regression models with externally estimated parameters.

In many regression applications, some of the model parameters are estimated from separate data sources. Typically, these estimates are plugged into the regression model and the remainder of the parameters is estimated from the primary data source. This situation arises frequently in compartment modeling when there is an external input function to the system. This paper provides asymptotic and bootstrap-based approaches for accounting for all sources of variability when computing standard errors for estimated regression model parameters. Examples and simulations are provided to motivate and illustrate the ideas.

Algorithms↗

PubMed2005

The effects of antipsychotic medication on factor and cluster structure of neurologic examination abnormalities in schizophrenia.

This study extends a previous study of the factor structure of the neurologic examination in unmedicated schizophrenia, utilizing cluster analysis and adding a medicated condition. We administered a modified version of the Neurologic Evaluation Scale (NES) on two occasions to 80 patients with schizophrenia or schizoaffective disorder, once while on antipsychotic medications and once while off medication. Data were distilled by combining right- and left-side scores, and by excluding rarely abnormal and unreliable items from the analysis. Principal components analysis yielded an intuitive four-factor solution in the unmedicated condition, but an inscrutable five-factor solution during medication. Cluster analysis revealed three groups: normal, cognitively impaired, and diffusely impaired. These results were also less interpretable with data from the medicated condition. Neurologic performance was better in the medicated than in the unmedicated condition. As is the case with other domains of symptoms and performance in schizophrenia, relationships among neurologic exam variables are altered by the presence of antipsychotic medication.

Adult↗

PubMed2005

Confirmatory factor analysis of the Neurological Evaluation Scale in unmedicated schizophrenia.

Factor structure of the Neurological Evaluation Scale (NES) was evaluated in 95 unmedicated patients with schizophrenia using confirmatory factor analysis (CFA). CFA was used to test four competing models that were based on prior empirical work examining the factor structure of the NES, as well as on theoretical considerations. A three-factor solution composed of "repetitive motor," "cognitive-perceptual," and "balance-tandem" factors best accounted for the data. These findings are consistent with prior exploratory studies that have suggested the NES is a multidimensional procedure that assesses diverse neurological domains. The current results contribute to the development of empirical subscales for neurological assessment procedures to be used in psychiatric conditions.

Adult↗