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Biomedical subjects

Wan C Tan

Publications and source records attributed to Wan C Tan.

11 recordsLinked to original sources
PubMed2006

IL-4 receptor genetic polymorphisms and asthma in Asian populations.

BACKGROUND: IL-4 receptor alpha chain is crucial for the binding and signaling of IL-4, which mediates isotype switching and IgE production. The gene of IL-4 receptor alpha chain is a candidate gene for asthma and atopy. OBJECTIVES: To determine whether Ile50Val and Q576R polymorphisms of IL-4 receptor alpha chain gene were associated with asthma and higher level of total IgE in Chinese, Malay and Indian populations. METHODS: About 303 physician-diagnosed asthmatic subjects (145 Chinese, 73 Malay, 85 Indian) and 355 unselected blood donors (157 Chinese, 98 Malay, 100 Indian) were recruited. Total serum IgE level was measured by ELISA. Genotypes of Ile50/Val and Q576R were determined by PCR and restriction enzyme length polymorphism (RFLP). RESULTS: Ile50Val heterozygote is less frequent in asthmatics than in controls in Malay population (P=0.007). No difference was found in Chinese and Indian population. Ile50/Ile50 was more prevalent in higher total serum IgE group (IgE>100IU/ml) in Malay. The prevalence of Ile50/R576 haplotype was lower in asthmatics than controls in Chinese (P=0.046); while the prevalence of Ile50/Q576 haplotype was lower in asthmatics than in controls in Malay (P=0.048). The frequencies of the two single nucleotide polymorphisms (SNPs) and haplotypes vary among ethnicities (P<0.05). CONCLUSION: IL-4RA gene polymorphisms and its haplotypes showed ethnic variations. The association between IL-4RA gene polymorphisms, its haplotypes and asthma differed from ethnicities.

Adult↗
PubMed2006

Implementing practice guidelines: a workshop on guidelines dissemination and implementation with a focus on asthma and COPD.

The present supplement summarizes the proceedings of the symposium "Implementing practice guidelines: A workshop on guidelines dissemination and implementation with a focus on asthma and COPD", which took place in Quebec City, Quebec, from April 14 to 16, 2005. This international symposium was a joint initiative of the Laval University Office of Continuing Medical Education (Bureau de la Formation Médicale Continue), the Canadian Thoracic Society and the Canadian Network for Asthma Care, and was supported by many other organizations and by industrial partners. The objectives of this meeting were to examine the optimal implementation of practice guidelines, review current initiatives for the implementation of asthma and chronic obstructive pulmonary disease (COPD) guidelines in Canada and in the rest of the world, and develop an optimal strategy for future guideline implementation. An impressive group of scientists, physicians and other health care providers, as well as policy makers and representatives of patients' associations, the pharmaceutical industry, research and health networks, and communications specialists, conveyed their perspectives on how to achieve these goals. This important event provided a unique opportunity for all participants to discuss key issues in improving the care of patients with asthma and COPD. These two diseases are responsible for an enormous human and socioeconomic burden around the world. Many reports have indicated that current evidence-based guidelines are underused by physicians and others, and that there are many barriers to an effective translation of recommendations into day-to-day care. There is therefore a need to develop more effective ways to communicate key information to both caregivers and patients, and to promote appropriate health behaviours. This symposium contributed to the initiation of what could become the "Canadian Asthma and COPD Campaign", aimed at improving care and, hence, the quality of life of those suffering from these diseases. It is hoped that this event will be followed by other meetings that focus on how to improve the transfer of key recommendations from evidence-based guidelines into current care, and how to stimulate research to accomplish this.

Asthma↗
PubMed2006

Effects of early intervention with inhaled budesonide on lung function in newly diagnosed asthma.

STUDY OBJECTIVES: Asthmatic patients lose lung function faster than normal subjects. The effectiveness of early intervention with inhaled corticosteroids on this decline in lung function is not established in recent-onset disease. DESIGN: The Inhaled Steroid Treatment as Regular Therapy in Early Asthma study was a randomized, double-blind study in 7,165 patients (5 to 66 years old), with persistent asthma for < 2 years to determine whether early intervention with low-dose inhaled budesonide prevents severe asthma-related events and the decline in lung function. Patients received budesonide (200 mug qd for children < 11 years old and 400 mug qd for others) or placebo for 3 years in addition to usual asthma medications. RESULTS: Treatment with budesonide significantly improved prebronchodilator and postbronchodilator FEV(1) percentage of predicted and reduced the mean declines from baseline for postbronchodilator FEV(1) at 1 year and 3 years: - 0.62% and - 1.79% for budesonide and - 2.11% and - 2.68% for placebo, respectively (p < 0.001). The decline was more marked for male patients, active smokers, and patients > 18 years old, and the smallest treatment effects were in adolescents. CONCLUSIONS: Long-term, once-daily treatment with low-dose budesonide improved both prebronchodilator and postbronchodilator FEV(1) in patients with recent-onset, persistent asthma, and reduced the loss of lung function over time.

Administration, Inhalation↗
PubMed2005

Viruses in asthma exacerbations.

PURPOSE OF REVIEW: Respiratory viruses are well recognized as major triggers of acute exacerbations of asthma in children and adults, resulting in frequent outpatients visits and hospitalizations. Clinical and epidemiologic evidence supports this association. The application of molecular diagnostic methods has improved understanding of viral epidemiology and the pathophysiological mechanisms involved in viral induced acute asthma. This article reviews publications since October 2002 for an update of the role of viruses in exacerbations of asthma. RECENT FINDINGS: Respiratory viruses are present in most patients hospitalized for life-threatening asthma and acute non life-threatening asthma. Rhinovirus is the most common, but coinfection with other viruses may be important. Patients with asthma are not more susceptible to upper respiratory tract rhinovirus infections than healthy people but suffer from more severe consequences of the lower respiratory tract infection. Recent epidemiologic studies suggest that viruses provoke asthma attacks by additive or synergistic interactions with allergen exposure or with air pollution. An impaired antiviral immunity to rhinovirus may lead to impaired viral clearance and hence prolonged symptoms. Respiratory viral infections cause asthmatic exacerbations by triggering recruitment of Th2-type cells into the lungs. There is no specific antiviral strategy for prevention of respiratory-triggered asthma exacerbations, although clinical trials of potential antiviral agents are ongoing. Indirect prevention strategies focus on the reduction of overall airway inflammation to reduce the severity of the host response to respiratory viral infections. SUMMARY: Respiratory viral infections are a major cause of morbidity and mortality in asthma. There is a lack of specific antiviral strategies in the prevention or reduction of viral-triggered asthma exacerbations. Recent advances in understanding of the epidemiology and immunopathogenesis of respiratory viral infection in asthma provide opportunities or identification of specific targets for antiviral agents and strategies for management and prevention.

Acute Disease↗
PubMed2004

Risk factors associated with habitual snoring and sleep-disordered breathing in a multi-ethnic Asian population: a population-based study.

INTRODUCTION: There is scant data on the risk factors of sleep-disordered breathing (SDB) in the general population in Asian countries. METHODS: Cross-sectional survey of a random population sample of 2298 adults aged 20-75 years, stratified by gender, ethnicity (Chinese, Malay and Indian) and age. An interviewer-administered questionnaire was used to elicit responses to questions on daytime somnolence and nocturnal events. Three categories of SDB were defined for analysis: habitual snoring; apnoeic snoring (SDB I); and apnoeic snoring or snoring with diurnal hypersomnia (SDB II). RESULTS: Snoring was reported by 201 persons (6.8%), SDB-I in 44 (1.9%) and SDB-II in 112 (4.9%) in the sample. The adjusted odds ratio (95% C.I.) of association with snoring were: male gender, 3.79 (2.69-5.33); older age (>60 years old), 2.15 (1.41-3.29); Indian versus Chinese, 1.54 (1.05-2.25); family history, 2.21 (1.56-3.12); obesity (BMI>30), 2.64 (1.62-4.30); neck circumference (>40 cm), 2.57 (1.59-4.11); and cigarette smoking, 2.05 (1.21-3.45). The risk factors for SDB were similar to that of snoring. CONCLUSION: Population risk factors associated with habitual snoring and SDB in Singapore are largely similar to those reported in other populations. Differential risks underscore the importance of ethnicity in determining the burden of SDB.

Adult↗
PubMed2004

Validation of the English version of the Asthma Quality of Life Questionnaire in a multi-ethnic Asian population.

The purpose of study was to assess the validity, reliability and acceptability of the English version of the Asthma Quality of Life Questionnaire in a multi-ethnic Asian population. The English version of the Standardized Asthma Quality of Life Questionnaire (AQLQ-S) and the Asthma Control Questionnaire (ACQ) were self-completed by 119 English-speaking Chinese, Malay and Indian asthmatic subjects, aged 17-78. Spirometric measurements, peak expiratory flow rate, current clinical symptoms and treatment requirements were documented. Reliability and responsiveness were analyzed in a subgroup of 57 patients who were reassessed 6 weeks later. The Cronbach alpha reliability coefficient for internal consistency of the AQLQ-S was 0.97 (0.96-0.98) for the overall score. The intraclass correlation coefficient (ICC) overall score was 0.97 (95% CI: 0.94-0.99) while the responsiveness index was 1.29 with strong longitudinal validity for clinical and spirometric measures of asthma severity and asthma control score (p < 0.001). The results of this study showed that the English version of the AQLQ-S is a sensitive and valid instrument for measuring health-related quality of life in asthmatic subjects from a multi-ethnic Asian population.

Adolescent↗
PubMed2003

Early intervention with budesonide in mild persistent asthma: a randomised, double-blind trial.

BACKGROUND: Although inhaled glucocorticosteroids are recommended for persistent asthma, their long-term effect on recent onset, mild, persistent asthma has yet to be established. METHODS: We did a randomised, double-blind clinical trial in 7241 patients in 32 countries to assess the effects of budesonide in patients who had had mild persistent asthma for less than 2 years and who had not had previous regular treatment with glucocorticosteroids. Patients aged 5-66 years received either budesonide or placebo once daily for 3 years in addition to their usual asthma medications. The daily budesonide dose was 400 microg, or 200 microg for children younger than 11 years. The primary outcome was time to first severe asthma-related event, and analysis was by intention to treat. FINDINGS: 198 of 3568 patients on placebo and 117 of 3597 on budesonide had at least one severe asthma exacerbation; hazard ratio 0.56 (95% CI 0.45-0.71, p<0.0001). Patients on budesonide had fewer courses of systemic corticosteroids and more symptom-free days than did those on placebo. Compared with placebo, budesonide increased postbronchodilator forced expiratory volume in 1 s (FEV1) from baseline by 1.48% (p<0.0001) after 1 year and by 0.88% (p=0.0005) after 3 years (expressed as percent of the predicted value). The corresponding increase in prebronchodilator FEV1 was 2.24% after 1 year and 1.71% after 3 years (p<0.0001 at both timepoints). The effect of treatment on all outcome variables was independent of the baseline lung function (prebronchodilator or postbronchodilator) or baseline medication. In children younger than 11 years, 3-year growth was reduced in the budesonide group by 1.34 cm. The reduction was greatest in the first year of treatment (0.58 cm) than years 2 and 3 (0.43 cm and 0.33 cm, respectively). INTERPRETATION: Long-term, once-daily treatment with low-dose budesonide decreases the risk of severe exacerbations and improves asthma control in patients with mild persistent asthma of recent onset.

Administration, Topical↗
PubMed2003

Epidemiology of respiratory viruses in patients hospitalized with near-fatal asthma, acute exacerbations of asthma, or chronic obstructive pulmonary disease.

PURPOSE: We compared the prevalence and spectrum of common respiratory viruses among patients with near-fatal asthma, acute exacerbations of asthma, or chronic obstructive pulmonary disease (COPD), and the relation of these findings to acute respiratory symptoms. METHODS: We obtained adequate samples of respiratory secretions from 17 patients hospitalized with near-fatal asthma, 29 with acute asthma, and 14 with COPD. We used a polymerase chain reaction-based method to test for six common respiratory viruses in samples from endotracheal tube aspirates from patients with near-fatal asthma, and from induced sputum specimens from patients with acute asthma or COPD. Respiratory symptoms (runny nose, sore throat, fever, chills, malaise, and cough) were recorded. Quiescent-phase induced sputum specimens were examined from patients who were initially virus positive. RESULTS: Viral nucleic acids were detected in 52% (31/60) of acute-phase specimens and 7% (2/29) of quiescent-phase specimens examined (P <0.001), with similar proportions of virus-positive patients during the acute phase in the three groups: 59% (10/17) of those with near-fatal asthma, 41% (12/29) with acute asthma, and 64% (9/14) with COPD. Picornavirus (47% [n = 8]) and adenovirus (24% [n = 4]) were most commonly identified in near-fatal asthma, whereas influenza virus (36% [n = 5]) predominated in COPD. Virus-positive patients had a significantly increased frequency of runny nose, sore throat, fever, chills, and malaise (odds ratio = 4.1 to 18; P = 0.02 to 0.001). CONCLUSION: Respiratory viruses are associated with hospitalizations for near-fatal asthma, acute asthma, and COPD, with some differences in the spectrum of viruses involved in the different groups of patients. Respiratory viruses are a target for the prevention and perhaps the treatment of these conditions.

Acute Disease↗
PubMed2003

Trends and ethnic differences in asthma hospitalization rates in Singapore, 1991 to 1998.

BACKGROUND: A few reports have indicated that asthma hospitalization rates in several countries have stopped rising or started falling in the 1990s. AIM: To describe recent trends and ethnic differences in asthma hospitalization rates in Singapore from 1991 to 1998. METHODS: Asthma hospitalization rates in all hospitals were analyzed by age groups, sex, ethnicity, and individual years, using aggregated data for asthma (ICD-9 493 and ICD-10 J45, J46) from 1991 to 1998, when nationwide data from the Central Claims Processing System were available. RESULTS: Between 1991 and 1998 there were a total of 37,615 hospital admissions for asthma, giving an annual average rate of 17.1 hospital admissions per 10,000 persons. Overall, the rates of asthma hospitalization fell by 28% from 21.7 per 10,000 in 1991 to 15.4 per 10,000 in 1998 (3.5% annually). The trends were broadly based across all age, sex, and ethnic groups. Hospitalizations were more common in boys than in girls aged 0 to 4 (male/female ratio 1.69), but less common in men than women aged 35 to 64 (male/female ratio 0.81). Rates of asthma hospital admissions were higher in Malays (32.8 per 10,000) and Indians (40.8 per 10,000) than Chinese (11.9 per 10,000). CONCLUSIONS: In line with findings from several countries, there have been recent declines in rates of hospital admissions for asthma in Singapore in the 1990s. The declines were broadly based across all population subgroups and parallel previously observed declines in mortality in adults. However, considerable ethnic differences in levels of asthma hospitalization still exist.

Adolescent↗
PubMed2002

Comparison of three methods for respiratory virus detection between induced sputum and nasopharyngeal aspirate specimens in acute asthma.

Viral respiratory tract infections are associated frequently with acute exacerbations of asthma. Nasopharyngeal aspirates and bronchoalveolar lavage specimens are used extensively for detecting viral respiratory tract infections, but not sputum. The aim of the study was to determine the efficiency of viral detection in induced sputum versus nasopharyngeal aspirate obtained during acute exacerbations of asthma, comparing three laboratory methods of viral diagnosis. Paired samples of induced sputum and nasopharyngeal aspirate obtained from 32 adults admitted to hospital with acute asthma were subjected to reverse transcription-polymerase chain reaction (RT-PCR), viral culture, and immunofluorescence assay. The results show that RT-PCR was associated with significantly higher rates of viral detection than culture (P=0.005) or immunofluorescence (P=0.001), without significant differences in the rates of viral detection between induced sputum and nasopharyngeal aspirate. It is concluded that induced sputum specimens are feasible for detection of viral respiratory tract infections by RT-PCR during acute exacerbations of asthma.

Acute Disease↗