Biomedical subjects

David Chiu

Publications and source records attributed to David Chiu.

3 recordsLinked to original sources

PubMed2006

Differentiation of Escherichia coli pathotypes by oligonucleotide spotted array.

To accurately determine the pathotypes of Escherichia coli strains, a comprehensive assessment of each strain that targets multiple genes is required. A new approach to the identification and characterization of E. coli pathotypes was developed by constructing gene-specific probes (70-mers) for not only the virulence genes associated with each E. coli pathotype but also the O157-, CFT073-, and K-12-specific and common genes of each pathotype. Analysis of oligonucleotide probes with reference and clinical isolates of E. coli pathotypes indicated that the array could differentiate the pathotypes on the basis of their virulence and specific gene patterns. Probes targeting common genes of E. coli were present in all the reference and clinical strains. Salmonella enterica subsp. enterica-specific genes and Salmonella core genes were used as negative controls. The entire E. coli pathotype showed reactivity to only 4 of the 81 Salmonella-specific gene probes. Characterization of the genetic and virulence profiles of a single strain by using probes for virulence factors and specific and common genes in the spotted array is an ideal diagnostic tool for determination of E. coli pathotypes and could also have a significant impact on the epidemiological analysis of E. coli infections.

DNA, Bacterial↗

PubMed2005

Effect of the Glycine Antagonist Gavestinel on cerebral infarcts in acute stroke patients, a randomized placebo-controlled trial: The GAIN MRI Substudy.

BACKGROUND AND PURPOSE: Gavestinel, GV150526, is a selective antagonist at the glycine site of the N-methyl-D-aspartate receptor. The safety and efficacy of GV150526 were studied in two phase III randomized placebo-controlled clinical trials of acute ischemic stroke patients within 6 h from onset [The Glycine Antagonist in Neuroprotection (GAIN) International and GAIN Americas Trials]. A planned MRI substudy within these trials investigated the effect of gavestinel on infarct volume. METHODS: Patients enrolled in the GAIN trials at designated MRI substudy sites were eligible if they had a pretreatment acute cortical lesion on diffusion-weighted MRI of at least 1.5 cm diameter or 5 cm(3). Final lesion assessment was performed on T(2)-weighted MRI at month 3. Blinded image analysis was performed centrally. The primary hypothesis was that gavestinel would attenuate lesion growth from baseline relative to placebo. RESULTS: A total of 106 patients were eligible, 75 (34 gavestinel, 41 placebo) of whom had month 3 scans (primary analysis population). No effects of gavestinel on infarct volume were observed in the primary or other analyses. However, significant associations of lesion volume to clinical severity and outcomes were observed. Ischemic lesion volume decrease was predictive of substantial clinical improvement. CONCLUSION: Consistent with the clinical outcomes in the GAIN trials, no effects of gavestinel on ischemic infarction was observed. Concordance of results of the clinical outcome trials with those of this infarct volume substudy as well the associations of infarct volume to clinical outcomes further support the potential role of infarct volume as a marker of outcome in dose finding and proof of principle acute stroke trials.

Cerebral Infarction↗

PubMed2004

Quality assurance system using statistical process control: an implementation for image cytometry.

AIMS: Optical technologies have shown some promise for improving the care of cervical neoplasia. We are currently evaluating fluorescence and reflectance spectroscopy and quantitative cyto-histopathology for cervical neoplasia screening and diagnosis. Here we describe the establishment and application of a quality assurance (QA) system for detecting system malfunctions and assessing the comparability of four image cytometers used in a multicenter clinical trial. METHODS: Our QA system involves three levels of evaluation based on the periodicity and complexity of the measurements. We implemented our QA system at three image cytometers at the British Columbia Cancer Agency and one at M.D. Anderson Cancer Center. The measurements or tasks were performed daily, monthly, and semi-annually. The current and voltage of the lamp, the calibration image characteristics, and the room temperature were checked daily. Long-term stability over time, short-term variability over time, and spatial response field uniformity were evaluated monthly. Camera linearity was measured semi-annually. Control charts based on statistical process control techniques were used to detect when the system did not perform optimally. RESULTS: Daily measurements have shown good consistency in room temperature, lamp and calibration behaviour. Monthly measurements have shown small coefficients of variation between and within the four devices. There have been greater differences between sessions than within sessions. Comparability among the four systems is reasonably good. Semi-annual measurements have shown stable camera linearity. QA events were detected using the QA system. Multiple examples of event detection leading to correction of system malfunction are described in this report. CONCLUSIONS: QA programs are critical for ensuring data integrity and therefore for the conduct of multicenter clinical trials.

Female↗