Biomedical subjects

Anne C Feng

Publications and source records attributed to Anne C Feng.

8 recordsLinked to original sources

PubMed2006

On the analysis and interpretation of outcome measures in stroke clinical trials: lessons from the SAINT I study of NXY-059 for acute ischemic stroke.

BACKGROUND AND PURPOSE: A variety of primary end points have been used in acute stroke trials. We focus on the modified Rankin Scale, a reliable and valid ordinal outcome measure that assesses disability on a 7-point scale. METHODS: We provide an abbreviated discussion of analytical methods for ordinal scales, and related effect size measures; we illustrate these methods and their interpretation with outcome data from the SAINT I study of NXY-059 in acute ischemic stroke. RESULTS: The nonparametric Mann-Whitney statistic provides a straightforward method for analysis of the modified Rankin Scale, and incorporates associated measures of effect size. These measures are directly related to the concepts of Number Needed to Treat and Number Needed to Harm. CONCLUSIONS: Our re-examination of the outcome data from the SAINT I study provides little evidence for the purported efficacy of NXY-059. More broadly, analysis and interpretation of ordinal outcome scales based on ascribed numerical values to the steps of the scale should be done cautiously. Statistical treatment of multiple primary outcome measures in acute stroke clinical trials should be established before analysis. Lastly, conflating statistical and clinical significance should be avoided.

Acute Disease↗

PubMed2006

Application of capture-recapture models to estimation of protein count in MudPIT experiments.

MudPIT is an automated shotgun proteomics approach that enhances the separation of peptides for sequencing by mass spectrometry analysis.We here adapt a mathematical model from ecology, namely, the capture-recapture model with a closed population and time-varying and heterogeneous individual probabilities of capture, to model the number of peptide identifications across the various cycles of a typical MudPIT experiment. In the absence of any prior information on abundance levels, the model can be used to estimate the total number of proteins in the experimental sample. We apply the model to a recent MudPIT-based experiment to estimate the total number of rat lung endothelial cell surface proteins. The model provides some practical guidelines for planning MudPIT experiments.

Animals↗

PubMed2005

Asymmetries in the spatial distributions of enhancing lesions and black holes in relapsing-remitting MS.

Magnetic resonance imaging (MRI) is the most important paraclinical test in the diagnosis of multiple sclerosis (MS) and for delineating its natural history. We investigate MRIs from a longitudinal study of 24 relapsing-remitting MS patients who had monthly MRI examinations for one year, and were not receiving active MS therapy during this period. We hypothesized that lesions occur randomly throughout the brain, and that patients are homogeneous with regard to spatial patterns of lesion presentation. We recorded the numbers and locations of enhancing lesions and hypointense lesions (black holes) in all scans, and found asymmetrical patterns of lesions about the mid-transaxial, mid-coronal, and mid-sagittal planes. Furthermore, in distinct subsets of patients, enhancing lesions and black holes tend to occur in the same locations. Clustering in lesion locations may be of functional significance, with consequent therapeutic implications.

Adult↗

PubMed2005

A note on generalized Genome Scan Meta-Analysis statistics.

BACKGROUND: Wise et al. introduced a rank-based statistical technique for meta-analysis of genome scans, the Genome Scan Meta-Analysis (GSMA) method. Levinson et al. recently described two generalizations of the GSMA statistic: (i) a weighted version of the GSMA statistic, so that different studies could be ascribed different weights for analysis; and (ii) an order statistic approach, reflecting the fact that a GSMA statistic can be computed for each chromosomal region or bin width across the various genome scan studies. RESULTS: We provide an Edgeworth approximation to the null distribution of the weighted GSMA statistic, and, we examine the limiting distribution of the GSMA statistics under the order statistic formulation, and quantify the relevance of the pairwise correlations of the GSMA statistics across different bins on this limiting distribution. We also remark on aggregate criteria and multiple testing for determining significance of GSMA results. CONCLUSION: Theoretical considerations detailed herein can lead to clarification and simplification of testing criteria for generalizations of the GSMA statistic.

Chromosome Mapping↗

PubMed2005

CT-ultrasound fusion prostate brachytherapy: a dynamic dosimetry feedback and improvement method. A report of 54 consecutive cases.

PURPOSE: The authors describe a prostate brachytherapy technique with dynamic dosimetry feedback, using coregistered CT and ultrasound (US) images, to map initial dosimetry deficiencies and guide remedial source placement. METHODS AND MATERIALS: Fifty-four consecutive patients treated with this method were analyzed for coregistration accuracy and dosimetry outcomes by evaluating the prostate V100, V150, D90, and urethral D50 and D10. Dosimetric improvements created by remedial source placement and preplan/postplan prostate D90 agreement were evaluated. RESULTS: Median CT-US coregistration discrepancy with this technique ranged from 0 to 4mm, with the posterior midline prostate and base prostate providing the least consistent and the urethra providing the most consistent coregistration agreement. Final prostate V100 values ranged from 96.1% to 99.8% for all patients. The addition of remedial sources directed by CT-US fusion produced V100 and D90 improvements whose magnitude inversely correlated with the initial result and exceeded the effect of adding quantitatively identical randomly distributed increased millicuries. The final prostate D90 result agreed within (-) 5% to (+) 10% of the preplan result in 98% of all patients. CONCLUSIONS: CT-US fusion prostate brachytherapy represents a dynamic dosimetry feedback and remediation method that consistently produced high prostate V100 and D90 values with acceptably low urethra D50 and D10 values in our study. The degree of prostate V100 and D90 dosimetry improvement created by remedial source placement effectively matched the degree of initial dosimetry deficiency. This method produced a high level of correlation between the preplan and final prostate D90 values.

Adult↗

PubMed2004

Prostate brachytherapy seed migration and dosimetry: analysis of stranded sources and other potential predictive factors.

PURPOSE: The purpose of this study was to evaluate the influence of potential contributing factors to the incidence of seed migration and quality of prostate brachytherapy dosimetry. METHODS AND MATERIALS: Sixty patients were evaluated with day one and 3-12 month plain films of the pelvis and chest, and day 1 CT-based dosimetry analysis. The incidence and types of seed migration were quantified. The seed migration outcome was evaluated with respect to source type (free vs. stranded), prostate volume, number of seeds, and needles. The day one prostate V100, V150, D90, and urethra D10 outcomes were evaluated with respect to source type, radiation type ((125)I vs. (103)Pd), prostate volume, prostate swelling, and quantity of migrating seeds. RESULTS: An increased incidence of day one and cumulative seed migration was predicted by free vs. stranded source type, with a relative risk of 6.97 and 3.08, respectively. Pulmonary and distal (toward the perineum) migration patterns were significantly reduced in the stranded group. An increased day one prostate V100, V150, D90, and urethra D10 outcome was predicted by stranded source type. CONCLUSION: Stranded source type was associated with decreased seed migration as well as higher prostate and urethra dosimetry values, resulting in an implant in which more radiation resided within the target volume, and less radiation metastasized to undesirable locations.

Brachytherapy↗

PubMed2003

Recursive partitioning as an approach to selection of immune markers for tumor diagnosis.

PURPOSE AND EXPERIMENTAL DESIGN: Cancer sera contain antibodies which react with a unique group of autologous cellular antigens called tumor-associated antigens (TAAs), but the low frequency of positive reactions against any individual antigen has precluded use of autoantibodies as useful diagnostic markers. With enzyme immunoassay, we examined antibody frequencies to a panel of seven TAAs, c-myc, cyclin B1, IMP1, Koc, p53, p62, and survivin, in 527 cancer patients (64 breast cancer patients, 45 colorectal cancers, 91 gastric cancers, 65 hepatocellular carcinomas, 56 lung cancers, and 206 prostate cancers), and 346 normals. We used recursive partitioning to assess whether we could accurately classify individuals as either cancer patients or normals on the basis of the profile of antibody reactivity to the seven TAAs for each individual. RESULTS: Recursive partitioning resulted in the selection of subsets of the seven-panel TAA, which differentiated between tumors and controls, and these subsets were unique to each cancer cohort. The classification trees had sensitivities ranging from 0.77 to 0.92 and specificities ranging from 0.85 to 0.91 in the cancer cohorts when normal means +2 SDs were used as standard cutoffs for immunoassay positivity. Antibody to cyclin B1 was the initial discriminating node for gastric and lung cancers, and for hepatocellular carcinoma, and was a subsequent discriminating node in all of the other cancer cohorts. c-myc was the initial discriminating node in breast cancer, p62 in prostate cancer, and IMP1 in colon cancer. Recursive partitioning demonstrated that no more than three of the seven TAAs were needed for any cancer cohort to arrive at these levels of sensitivity and specificity. CONCLUSIONS: This initial study shows that multiple antigen miniarrays can provide accurate and valuable tools for cancer detection and diagnosis. Performance of the miniarrays might be enhanced by other combinations of TAAs appropriately selected for different cancer cohorts.

Antibodies, Neoplasm↗

PubMedDate not supplied

Seasonal variations in exacerbations and MRI parameters in relapsing-remitting multiple sclerosis.

Environmental factors may be involved in the etiology of multiple sclerosis (MS). We investigate prevalence of exacerbations and MRI findings in a cohort of relapsing-remitting multiple sclerosis patients, for evidence of seasonal variation or cyclic trends. We find only weak evidence of seasonality in our data. Differences in reports of seasonal variation in multiple sclerosis disease activity may be due to regional climatic differences or other geographic variables that change with latitude as well as genetic predisposition.

Adult↗