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Biomedical subjects

K Y Fung

Publications and source records attributed to K Y Fung.

At least 19 recordsLinked to original sources
PubMed2005

Management of malignant atlanto-axial tumours.

PURPOSE: To review the management and outcomes of patients with malignant tumours of the atlanto-axial spine treated over a 4-year period at a tertiary hospital. METHODS: A total of 12 patients (9 female and 3 male) with a mean age of 56.5 years (range, 35-71 years) were consecutively enrolled. At the time of presentation, 7 patients had received treatment for a known primary malignancy of the lung (n=4), colon (n=1), nasopharynx (n=1), or breast (n=1). The atlanto-axial spine was the first presentation of malignant disease in the remaining 5 patients, whose subsequent diagnoses were multiple myeloma (n=1), carcinoma of the thyroid (n=1), malignant fibrous histiocytoma (n=2), and adenocarcinoma of unknown origin (n=1). Preoperative, postoperative, and follow-up radiographs and computed tomographic and magnetic resonance imaging scans were analysed with regard to the extent of tumour involvement, other spinal metastases, instability, and evidence of cord compression. Surgeries were performed for surgically fit patients with a life expectancy of more than 3 months. RESULTS: All patients presented with severe suboccipital neck pain. Two had mild neurological deficits (Frankel grade D). Two patients were treated conservatively with rigid neck collars and survived for 3 and 11 months. Surgical stabilisation with posterior instrumentation was performed in 10 patients. One patient received additional anterior surgery for tumour debulking and bone grafting. No neurological complications were recorded in the series. Excellent relief of pain was achieved, and the mean visual analogue scale pain score of the operated patients improved from 9.3 to 1.9. The mean survival of 9 patients after surgery was 13.1 months, while one patient was still living at the time of review (at postoperative 11 months). CONCLUSION: Surgical stabilisation in selected patients provided pain relief and preserved ambulatory status before the deterioration of overall function.

Adult↗
PubMed2002

Recurrent BRCA1 and BRCA2 germline mutations in ovarian cancer: a founder mutation of BRCA1 identified in the Chinese population.

Previous mutational analysis for BRCA gene mutations in sporadic ovarian cancer occurring in Chinese patients in Hong Kong identified six germline BRCA1 mutations and one germline BRCA2 mutation, six of which were novel (Khoo et al., 2000). Knowledge of BRCA gene mutations in the Chinese population is relatively scant. In this study, we focussed on whether any of these mutations could be recurrent in our Chinese population, making use of archival paraffin embedded tissue. A consecutive series of 214 ovarian cancer cases, half of Southern Chinese origin from Hong Kong whilst the other half of Northern Chinese origin from Beijing were used for the study. We identified one further novel mutation, 1081delG, in BRCA1. This was found to occur in two unrelated individuals with shared haplotype as revealed by allelotype analysis, thus demonstrating founder effect. Two other recurrent mutations were also identified, the 2371-2372delTG mutation in BRCA1 and the 3337C>T mutation in BRCA2 recurring in two and three unrelated individuals respectively, giving an overall prevalence 4.7% of recurrent BRCA mutations in ovarian cancer in the Southern Chinese population. Most importantly, all our recurrent mutation carriers were identified from Southern Chinese patients from Hong Kong whilst such mutations were absent in samples from the Northern Chinese. Our findings indicate possible heterogeneity in the BRCA genotype between Northern and Southern Chinese. The identification of a founder mutation and two recurrent mutations moreover, has important implications towards screening strategies for breast and ovarian cancer among Chinese of southern ancestral origin who are now dispersed throughout the world.

Adult↗
PubMed2002

Robust active control of broadband noise in finite ducts.

This study focuses on robust active control of broadband noise in finite ducts. Our analytical and experimental studies suggest the existence of several technical flaws in the path models of conventional active noise control (ANC) systems. These are sensitivity of the path model with respect to boundary conditions, and nonminimum phase (NMP) secondary and reference paths. For finite ducts with small cross sections, the traveling wave model (TWM) may be adopted to find an effective solution to these problems and lead to a robust ANC system. Since many practical "noisy" ducts are finite with small cross sections, the proposed ANC has many practical applications. Its robustness and ability to suppress broadband noise will be explained theoretically and verified experimentally.

Journal Article↗
PubMed2001

Beliefs and perceptions of patients with acne.

BACKGROUND: There is a paucity of information on the knowledge and understanding of patients with acne about their condition. OBJECTIVE: The objective of this study is to evaluate the knowledge, beliefs, and perceptions of acne patients regarding their understanding of acne pathogenesis, sources of information, treatment options, and expectations. METHODS: Patients referred to a community-based dermatologist for management of acne vulgaris completed a self-administered questionnaire. Responses were correlated with demographic and clinical information. RESULTS: Seventy-four percent of patients waited more than 1 year before seeking medical attention for acne. Nonprescription products used most frequently were cleansers, acne pads, and lotions. Acne was most often believed to be caused by hormonal and genetic factors, although diet, poor skin hygiene, and infection were also implicated. Information on acne was obtained primarily from family physicians, mass media, friends, and family, but was largely believed to be inadequate. Acne was believed to be curable by 49% of patients with an anticipated treatment duration of less than 6 months. Male patients and those with severe acne preferred systemic therapy compared with female patients and those with lesser grades of acne. CONCLUSION: There is a need for accessible, accurate, community-based education on the natural history of acne, pathogenesis, risk of sequelae, the effectiveness and expected duration of treatment, and the importance of prompt medical attention.

Acne Vulgaris↗
PubMed1999

Evaluation of regression calibration and SIMEX methods in logistic regression when one of the predictors is subject to additive measurement error.

BACKGROUND: This paper presents an evaluation of two methods of measurement error adjustment based on recently-developed computer routines (RCAL and SIMEX) under logistic regression models, when one of the two predictors is subject to additive measurement error or Berkson error. METHODS: Computer simulations were used to generate data under a variety of conditions and the methods compared in terms of bias, mean squared error and confidence interval coverage of the regression estimates. RESULTS: Based on our investigations, RCAL was shown to perform very well in all situations considered, except in the presence of Berkson error when the predictor variables were highly correlated. CONCLUSIONS: Since measurement error can lead to misleading inference, it is important to adjust for measurement error in the application of logistic regression. Until better measurement error adjustment methods become available, we recommend RCAL on the basis of our simulation results.

Algorithms↗
PubMed1998

Use of generalized linear mixed models in analyzing mutant frequency data from the transgenic mouse assay.

The transgenic mouse assay is now widely used for the study of mutagenesis in diverse rodent tissues and to test chemicals for genotoxic potential. This kind of assay generally involves nested observations at several levels of sampling, e.g., animals, packaging reactions, and plates. Due to the common origin, the mutant frequency (MF) in tissues from the same animal are likely to be positively correlated, inducing extra variation relative to the common binomial variation. In this article, a generalized linear mixed model is used to analyze the overdispersed binomial data on mutant frequency from the transgenic mouse assay, with a random effect for each level of the sampling hierarchy. This is a comprehensive framework within which different sources of variation in the data can be evaluated in nested factorial experiments and treatment effects can be assessed simultaneously. It avoids the current practice of repeated testing for excess binomial variability at each level of the sampling hierarchy and aggregating data up the levels, but fits the data with one single model. Parameters associated with the fixed effects, particularly dose, and the variance components for the random effects (e.g., animals, packages, and plates) can be estimated and tested for significance. Data previously reported in the literature involving the lacl gene from the Big Blue mouse are used to illustrate the proposed method.

Animals↗
PubMed1998

Statistical analysis of lacZ mutant frequency data from MutaMouse mutagenicity assays.

Transgenic mouse assays have provided an unprecedented opportunity to study mutagenesis in diverse rodent tissues. In this article data from MutaMouse mutagenicity assays based on the Escherichia coli gene lacZ were analyzed systematically using liver and bone marrow as potential target tissues. Sources of variation, including plates (within packaging reactions), packaging reactions (within animals) and animals, were evaluated for extra-binomial variation. Although hardly any evidence of overdispersion was detected at the plate level, limited evidence of extra-binomial variation was observed at the packaging reaction level. There was, however, much stronger evidence of overdispersion at the animal level. Statistical tests for increasing trend in mutant frequency with increasing dose were also performed at the animal level. A significant increasing trend following exposure to N-nitrosodibenzylamine was detected in liver but not in bone marrow. A logistical model was used to further describe the dose-response relationship observed in N-nitrosodibenzylamine-treated liver tissue.

Administration, Oral↗
PubMed1998

A comparison of methods for estimating the benchmark dose based on overdispersed data from developmental toxicity studies.

Developmental anomalies resulting from prenatal toxicity can be manifested in terms of both malformations among surviving offspring and prenatal death. Although these two endpoints have traditionally been analyzed separately in the assessment of risk, multivariate methods of risk characterization have recently been proposed. We examined this and other issues in developmental toxicity risk assessment by evaluating the accuracy and precision of estimates of the effective dose (ED05) and the benchmark dose (BMD05) using computer simulation. Our results indicated that different variance structures (Dirichlet-trinomial and generalized linear model) used to characterize overdispersion yielded comparable results when fitting joint dose response models based on generalized estimating equations. (The choice of variance structure in separate modeling was also not critical.) However, using the Rao-Scott transformation to eliminate overdispersion tended to produce estimates of the ED05 with reduced bias and mean squared error. Because joint modeling ensures that the ED05 for overall toxicity (based on both malformations and prenatal death) is always less than the ED05 for either malformations or prenatal death, joint modeling is preferred to separate modeling for risk assessment purposes.

Abnormalities, Drug-Induced↗
PubMed1997

Statistical analysis of the lacI transgenic mouse mutagenicity assay.

The transgenic mouse assay is now widely used to test chemicals for genotoxic potential. In this article, we consider statistical tests for increasing trend in mutant frequency with increasing dose, along with statistical models that may be used to describe the observed dose-response relationships. The application of these methods is illustrated using data on 2-acetylaminofluorene, di(2-ethylhexyl)phthalate, heptachlor, and sodium phenobarbital. No strong evidence of extra-binomial variation was detected at the plate level, but greater evidence was noted when the data were aggregated to the package or animal level in liver, necessitating the use of statistical methods that allow for overdispersion relative to binomial variation. Clear increase on mutant frequency induced by 2-acetylaminofluorene was detected in both liver and bladder, but no apparent trends were noted with di(2-ethylhexyl)phthalate, heptachlor, and sodium phenobarbital. The exponential model provides a good fit to the observed dose-response relationship in liver, whereas a Weibull model provides a better fit for bladder.

2-Acetylaminofluorene↗
PubMed1997

Management of fulminant hepatic failure at Queen Mary Hospital.

OBJECTIVE: To evaluate the strategy of the management of patients with fulminant hepatic failure at Queen Mary Hospital. METHODS: In the period 1994 through 1996, 30 patients with fulminant hepatic failure were managed by active supportive treatment in the Intensive Care Unit in preparation for liver transplantation. Liver transplantation was performed in 14 patients (aged 17-47), 3 of whom received liver grafts from brain-stem dead donors and 11 received live-related grafts from family members. The median duration from admission to liver transplantation was 3 days (range: 1-6 days). RESULTS: Thirteen patients (93%) survived the liver transplantation and are well after a median period of follow-up of 7 months. The only mortality was in a patient with pre-exiting renal transplantation and hepatitis B infection, who died from intra-abdominal candidiasis. CONCLUSION: The strategy of active supportive treatment and early liver transplantation using live-related liver graft is probably the key to the success of the management of fulminant hepatic failure in our series.

Adolescent↗
PubMed1996

Spinal epidural abscess: a report of nine cases and the use of intra-operative ultrasonography.

BACKGROUND: Spinal epidural abscess is an uncommon and dangerous lesion. Once neurological complications occur the damage is often irreversible. METHODS: The clinical presentation, operative findings, management and follow up of nine cases of spinal epidural abscess were reported. Four patients were diabetic and four others were intravenous drug addicts. The last patient had a history of a protracted stay in an intensive care unit complicated by pneumonia and pleural effusion. Ultrasonography was used intraoperatively to guide and to assess the adequacy of drainage and decompression of the epidural abscess. RESULTS: Multiple level laminectomy was necessary and Staphylococcus aureus was the most common organism cultured. None of the five patients presenting with acute complete paralysis regained neurological function. Two of the four patients with incomplete paralysis were able to walk with an aid. CONCLUSIONS: Spinal epidural abscess usually presents late and the prognosis is generally poor. Ultrasound may be useful in determining the extent of the abscess during operation to drain the collection.

Abscess↗
PubMed1994

Tests for trend in developmental toxicity experiments with correlated binary data.

In this article, the operating characteristics of recently proposed tests for trend in correlated binary data arising in laboratory studies of developmental toxicity are examined using both computer-generated and experimental data. Specifically, we consider adjusted Cochran-Armitge tests based on the Rao-Scott transformation which are of the same general form as that for uncorrelated data. In addition, generalized score tests based on generalized estimating equations allowing for extrabinomial variation in the data are discussed. Specific forms of these statistics demonstrating favorable type I and type II error rates are identified and recommended for use in practice. The application of these tests is illustrated using data from studies of developmental toxicity that have been reported in the literature.

Abnormalities, Drug-Induced↗
PubMed1984

Methodological issues in case-control studies. III--The effect of joint misclassification of risk factors and confounding factors upon estimation and power.

The effect of joint misclassification of polytomous risk factors and polytomous covariates in case-control studies upon estimation and power has been examined using computer simulation and mathematical models. It is concluded that non-differential misclassification of covariates may be as important as non-differential misclassification of exposure variables, and that the resultant bias of the relative risk estimate may be either toward or away from the null. It is pointed out that when a confounding variable is misclassified the calculated p value from the particular study will be incorrect and may either be too large or too small depending on the nature of the confounding.

Clinical Trials as Topic↗
PubMed1976

Cytotoxicity in graft-versus-host reaction. II. Lysis of target cells of parental genotyppe by F1 hybrid macrophages.

Graft-versus-host (GVH) reactions were induced in adult F1 hybrid mice with the i.p. injection of parental strain spleen cells. Peritoneal exudate and spleen cells of the F1 hybrids taken 8 days after the induction of GVH reaction had a nonspecific in vitro cytotoxic effect which was measured by using 51Cr-labeled target cells of parental genotype. The cytotoxic cells in the peritoneal exudates were shown to be macrophages which adhered to plastic surfaces and were sensitive to the toxic action of crystalline silica particles. Moreover, the injection of partially purified syngeneic macrophages into the F1 hybrids undergoing GVH reactions increased the cytotoxic activity of the peritoneal exudate cells obtained from these animals. These results suggest that during GVH reaction host macrophages are activated into a state of nonspecific cytotoxicity.

Animals↗
PubMedDate not supplied

Attitudes of female patients regarding oral contraceptives for treatment of acne.

BACKGROUND: Two hormonal agents with contraceptive properties are currently indicated in Canada for treatment of acne. OBJECTIVE: The purpose of this study was to determine the attitudes and concerns of female patients regarding the use of hormonal agents and oral contraceptives in treatment of acne. METHODS: A self-completed questionnaire was administered to all female acne patients of a community-based dermatologist over a 10-week period between June and August 1999. Statistical analysis was performed by chi-square testing at the 5% significance level. RESULTS: Eighty-six percent recognized that oral contraceptives ("birth control pills") were also used as a treatment for acne and 60% were willing to use this form of treatment. The most common concern regarding the use of oral contraceptives were side effects (80%). Younger patients were seven times more likely to be concerned about potential disapproval or misunderstanding on the part of others regarding the use of these medications (p approximately 0.01). CONCLUSION: Female acne patients recognize that oral contraceptives are useful in treatment of acne. Although side effects of these medications are of general concern, social disapproval is of particular concern to younger patients.

Acne Vulgaris↗
PubMedDate not supplied

Rapid on-site defibrillation versus community program.

INTRODUCTION: For patients who suffer out-of-hospital cardiac arrest, the time from collapse to initial defibrillation is the single most important factor that affects survival to hospital discharge. The purpose of this study was to compare the survival rates of cardiac arrest victims within an institution that has a rapid defibrillation program with those of its own urban community, tiered EMS system. METHODS: A logistic regression analysis of a retrospective data series (n = 23) and comparative analysis to a second retrospective data series (n = 724) were gathered for the study period September 1994 to September 1999. The first data series included all persons at Casino Windsor who suffered a cardiac arrest. Data collected included: age, gender, death/survival (neurologically intact discharge), presenting rhythm (ventricular fibrillation (VF), ventricular tachycardia (VT), or other), time of collapse, time to arrival of security personnel, time to initiation of cardiopulmonary resuscitation (CPR) prior to defibrillation (when applicable), time to arrival of staff nurse, time to initial defibrillation, and time to return of spontaneous circulation (if any). Significantly, all arrests within this series were witnessed by the surveillance camera systems, allowing time of collapse to be accurately determined rather than estimated. These data were compared to those of similar events, times, and intervals for all patients in the greater Windsor area who suffered cardiac arrest. This second series was based upon the Ontario Prehospital Advanced Life Support (OPALS) Study database, as coordinated by the Clinical Epidemiology Unit of the Ottawa Hospital, University of Ottawa. RESULTS: The Casino Windsor had 23 cases of cardiac arrests. Of the cases, 13 (56.5%) were male and 10 (43.5%) were female. All cases (100%) were witnessed. The average of the ages was 61.1 years, of the time to initial defibrillation was 7.7 minutes, and of the time for EMS to reach the patient was 13.3 minutes. The presenting rhythm was VF/VT in 91% of the case. Fifteen patients were discharged alive from hospital for a 65% survival rate. The Greater Windsor Study area included 668 cases of out-of-hospital cardiac arrest: Of these, 410 (61.4%) were male and 258 (38.6%) were female, 365 (54.6%) were witnessed, and 303 (45.4%) were not witnessed. The initial rhythm was VF/VT was in 34.3%. Thirty-seven (5.5%) were discharged alive from the hospital. CONCLUSION: This study provides further evidence that PAD Programs may enhance cardiac arrest survival rates and should be considered for any venue with large numbers of adults as well as areas with difficult medical access.

Aged↗