Electrocardiographic changes with ziprasidone.
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Biomedical subjects
Cynthia Siu
Publications and source records attributed to Cynthia Siu.
The use of weighted Z-tests in medical research.
Traditionally the un-weighted Z-tests, which follow the one-patient-one-vote principle, are standard for comparisons of treatment effects. We discuss two types of weighted Z-tests in this manuscript to incorporate data collected in two (or more) stages or in two (or more) regions. We use the type A weighted Z-test to exemplify the variance spending approach in the first part of this manuscript. This approach has been applied to sample size re-estimation. In the second part of the manuscript, we introduce the type B weighted Z-tests and apply them to the design of bridging studies. The weights in the type A weighted Z-tests are pre-determined, independent of the prior observed data, and controls alpha at the desired level. To the contrary, the weights in the type B weighted Z-tests may depend on the prior observed data; and the type I error rate for the bridging study is usually inflated to a level higher than that of a full-scale study. The choice of the weights provides a simple statistical framework for communication between the regulatory agency and the sponsor. The negotiation process may involve practical constrains and some characteristics of prior studies.
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Improvement in cognitive function following a switch to ziprasidone from conventional antipsychotics, olanzapine, or risperidone in outpatients with schizophrenia.
OBJECTIVE: To assess changes in cognitive function in stable outpatients with schizophrenia switched to ziprasidone from conventional antipsychotics (n = 108), olanzapine (n = 104), or risperidone (n = 58) because of suboptimal efficacy or poor tolerability. METHODS: In three separate 6-week trials, patients received ziprasidone 40 mg b.i.d. for 2 days, followed by 20-80 mg b.i.d. for the next 40 days. Before switching, and at endpoint, patients were evaluated with tests of working and secondary verbal memory, vigilance, visuomotor speed, verbal fluency, and executive functioning. Principal components factor analysis was performed to test for clustering of cognitive variables. RESULTS: Significant improvements were seen at endpoint in secondary verbal memory (in all three groups), vigilance (in patients switched from conventional antipsychotics or risperidone), executive function (in patients switched from conventional antipsychotics or risperidone), and verbal fluency. Factor analysis on baseline scores suggested reduction of the cognitive variables to three factors: verbal skills, attention and short-term memory, and executive functioning. Analysis of z-transformed mean change in factor scores showed significant improvement in verbal skills and global score following the switch from conventional antipsychotics, olanzapine, or risperidone. CONCLUSIONS: Patients requiring a change in antipsychotic therapy may exhibit cognitive improvement following a switch to ziprasidone.
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Improvement in prosocial functioning after a switch to ziprasidone treatment.
BACKGROUND: Cognitive, social, and affective impairments are major features of schizophrenia, despite not being represented in the formal diagnostic criteria. These impairments are associated with major reductions in quality of life for patients with schizophrenia. Treatment with newer antipsychotic medications has been reported to improve all of these areas of functioning, but most studies have not examined the direct association between changes in cognitive functioning and other aspects of the illness. OBJECTIVES: The goal of this analysis was to examine relationships between cognitive and affective symptoms and their impact on social impairments in patients switched to ziprasidone treatment. METHODS: In this study, which is a re-analysis of previously published data, 270 patients were switched from previous treatment with conventional antipsychotics, risperidone, or olanzapine to treatment with ziprasidone. Patients were tested with a cognitive assessment battery, rated with the Positive and Negative Syndrome Scale (PANSS), and received other assessments of safety and tolerability. PANSS scores were divided into factors based on previously published factor analyses, with a focus on the cognitive, prosocial, and anxiety-depression factors. RESULTS: Statistically significant improvements for global cognitive functioning and the three PANSS subscales were found across the studies. When the data were pooled for a path analysis, changes in cognitive functioning indexed by the PANSS cognitive subscales was the primary predictor of improvements in PANSS prosocial functions, with changes in anxiety-depression accounting for much less variance. CONCLUSION: These results suggest a direct relationship between improvements in cognitive and prosocial functioning in patients with schizophrenia and indicate that treatments that enhance cognitive functioning, such novel antipsychotics, have the potential to improve aspects of outcome in schizophrenia even in short-term treatment studies. This issue should be addressed in future double-blind studies of the effects of atypical medications in schizophrenia.
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