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Biomedical subjects

Yin Bun Cheung

Publications and source records attributed to Yin Bun Cheung.

At least 19 recordsLinked to original sources
PubMed2007

Developmental potential in the first 5 years for children in developing countries.

Many children younger than 5 years in developing countries are exposed to multiple risks, including poverty, malnutrition, poor health, and unstimulating home environments, which detrimentally affect their cognitive, motor, and social-emotional development. There are few national statistics on the development of young children in developing countries. We therefore identified two factors with available worldwide data--the prevalence of early childhood stunting and the number of people living in absolute poverty--to use as indicators of poor development. We show that both indicators are closely associated with poor cognitive and educational performance in children and use them to estimate that over 200 million children under 5 years are not fulfilling their developmental potential. Most of these children live in south Asia and sub-Saharan Africa. These disadvantaged children are likely to do poorly in school and subsequently have low incomes, high fertility, and provide poor care for their children, thus contributing to the intergenerational transmission of poverty.

Adolescent↗
PubMed2007

Epidemiology of tuberculosis in a high HIV prevalence population provided with enhanced diagnosis of symptomatic disease.

BACKGROUND: Directly observed treatment short course (DOTS), the global control strategy aimed at controlling tuberculosis (TB) transmission through prompt diagnosis of symptomatic smear-positive disease, has failed to prevent rising tuberculosis incidence rates in Africa brought about by the HIV epidemic. However, rising incidence does not necessarily imply failure to control tuberculosis transmission, which is primarily driven by prevalent infectious disease. We investigated the epidemiology of prevalent and incident TB in a high HIV prevalence population provided with enhanced primary health care. METHODS AND FINDINGS: Twenty-two businesses in Harare, Zimbabwe, were provided with free smear- and culture-based investigation of TB symptoms through occupational clinics. Anonymised HIV tests were requested from all employees. After 2 y of follow-up for incident TB, a culture-based survey for undiagnosed prevalent TB was conducted. A total of 6,440 of 7,478 eligible employees participated. HIV prevalence was 19%. For HIV-positive and -negative participants, the incidence of culture-positive tuberculosis was 25.3 and 1.3 per 1,000 person-years, respectively (adjusted incidence rate ratio = 18.8; 95% confidence interval [CI] = 10.3 to 34.5: population attributable fraction = 78%), and point prevalence after 2 y was 5.7 and 2.6 per 1,000 population (adjusted odds ratio = 1.7; 95% CI = 0.5 to 6.8: population attributable fraction = 14%). Most patients with prevalent culture-positive TB had subclinical disease when first detected. CONCLUSIONS: Strategies based on prompt investigation of TB symptoms, such as DOTS, may be an effective way of controlling prevalent TB in high HIV prevalence populations. This may translate into effective control of TB transmission despite high TB incidence rates and a period of subclinical infectiousness in some patients.

AIDS-Related Opportunistic Infections↗
PubMed2006

Nursing and community rates of Mycobacterium tuberculosis infection among students in Harare, Zimbabwe.

BACKGROUND: African hospitals have experienced major increases in admissions for tuberculosis, but they are ill-equipped to prevent institutional transmission. We compared institutional rates and community rates of tuberculin skin test (TST) conversion in Harare, Zimbabwe. METHODS: We conducted a cohort study of TST conversion 6, 12, and 18 months into training among 159 nursing and 195 polytechnic school students in Harare. Students had negative TST results (induration diameter, < or =9 mm) with 2-step testing at the start of training. RESULTS: Nursing students experienced 19.3 TST conversions (increase in induration diameter, > or =10 mm) per 100 person-years (95% confidence interval [CI], 14.2-26.2 conversions per 100 person-years), and polytechnic school students experienced 6.0 (95% CI, 3.5-10.4) conversions per 100 person-years. The rate of difference was 13.2 conversions (95% CI, 6.5-20.0) per 100 person-years. With a more stringent definition of conversion (increase in the induration diameter of > or =10 mm to at least 15 mm), which is likely to increase specificity but decrease sensitivity, conversion rates were 12.5 and 2.8 conversions per 100 person-years in nursing and polytechnic school students, respectively (rate difference, 9.7 conversions per 100 person-years; 95% CI, 4.5-14.8 conversions per 100 person-years). Nursing students reportedly nursed 20,868 inpatients with tuberculosis during 315 person-years of training. CONCLUSIONS: Both groups had high TST conversion rates, but the extremely high rates among nursing students imply high occupational exposure to Mycobacterium tuberculosis. Intense exposure to inpatients with tuberculosis was reported during training. Better prevention, surveillance, and management of institutional M. tuberculosis transmission need to be supported as part of the international response to the severe human immunodeficiency virus infection epidemic and health care worker crisis in Africa.

BCG Vaccine↗
PubMed2006

Bivariate poisson-poisson model of zero-inflated absenteeism data.

Bimodal distributions of counts with one mode at zero are often seen in medical research. In a health survey parents were asked the number of days their children missed their activities (Y(1)) and the number of days their children spent in bed (Y(2)) due to illness in the past four weeks. Both variables exhibited zero inflation. We consider a bivariate Poisson-Poisson regression model, in which the two variables are regarded as indicators of an unobserved health status variable. Based on this, we further develop a bivariate Poisson-Poisson model that constrains Y(1)>or=Y(2). It is often claimed that there is a critical window of growth and nutrition in foetal life and infancy during which subsequent health status is affected. It is not clear whether the claim is true and whether childhood growth matters more. We analyse the bivariate data in relation to weight-for-age in infancy and weight gain from infancy to age 7 years. The findings do not support the existence of a critical window in infancy. There is some indication that childhood weight gain might affect health status.

Absenteeism↗
PubMed2006

EGFR Intron 1 polymorphism in Asian Populations and its correlation with EGFR gene expression and amplification in breast tumor tissues.

AIM: The purpose of this study was to test the hypothesis if longer CA dinucleotide repeats are more common in the Asian population and also to gain insights into the interplay between the CA dinucleotide repeats and the frequencies of EGFR gene expression and amplifications as this might have therapeutic implications with regards to treatment with tyrosine kinase inhibitors. MATERIALS AND METHODS: The EGFR intron 1 polymorphism was analysed in three distinct healthy Asian subjects, namely, Chinese (N = 96), Malays (N = 98) and Indians (N = 100). Comparative genomic hybridisation was performed to investigate for changes in DNA copy number in relation to the polymorphic CA dinucleotide repeats in breast tumor tissues (N = 22). RESULTS: The frequency of short alleles with 14 and 15 CA repeats were most common in the Asian populations and significantly higher than those reported for Caucasians. The frequency of 20 CA repeats was 5%, almost 13-fold lower than previous reports. EGFR amplifications were detected in 23% and 11% of breast tumor tissues harboring short and long CA repeats, respectively. CONCLUSION: Our results show that the frequency of alleles encoding for short CA dinucleotide repeats is common in Asian populations. EGFR expression and amplification levels were also higher in Asian breast tumor tissues with short CA dinucleotide repeats. These findings suggest that the EGFR intron 1 polymorphism may influence response to treatment with tyrosine kinase inhibitors in breast cancer patients and further studies are warranted.

Asian People↗
PubMed2006

Growth and cognitive function of Indonesian children: Zero-inflated proportion models.

This is a study of the cognitive function of Indonesian children. The cognitive function assessment consisted of 17 items and the number of correct answers a child could score therefore ranged between 0 and 17. In this upper bounded situation, a zero-inflated binomial model and a zero-inflated beta-binomial model were considered. The purpose of the analysis was to examine whether the growth status in infancy and at the age of 7 years was related to the cognitive function of the children. The four regression models proposed by Lucas, Fewtrell and Cole were fitted, i.e. an 'early model' relating early body size to the outcome, a 'later model' relating later body size to the outcome, a 'combined model' including both early and later anthropometry measures, and an 'interaction model' further including an interaction term calculated as the product of early and later body size. It was found that social variables predicted the probability of zero-inflation, while weight-for-age at 7 years predicted the proportion of correct answers. The results do not support the existence of a critical window of cognitive development in infancy. Rather they suggest that it is the lack of catch-up growth after poor growth in infancy that is hazardous, and that childhood weight gain is influential regardless of weight in infancy.

Body Weight↗
PubMed2006

Long-term impact of malaria chemoprophylaxis on cognitive abilities and educational attainment: follow-up of a controlled trial.

OBJECTIVES: We investigated the long-term impact of early childhood malaria prophylaxis on cognitive and educational outcomes. DESIGN: This was a household-based cluster-controlled intervention trial. SETTING: The study was conducted in 15 villages situated between 32 km to the east and 22 km to the west of the town of Farafenni, the Gambia, on the north bank of the River Gambia. PARTICIPANTS: A total of 1,190 children aged 3-59 mo took part in the trial. We traced 579 trial participants (291 in the prophylaxis group and 288 in the placebo group) in 2001, when their median age was 17 y 1 mo (range 14 y 9 mo to 19 y 6 mo). INTERVENTIONS: Participants received malaria chemoprophylaxis (dapsone/pyrimethamine) or placebo for between one and three malaria transmission seasons from 1985 to 1987 during the controlled trial. At the end of the trial, prophylaxis was provided for all children under 5 y of age living in the study villages. OUTCOME MEASURES: The outcome measures were cognitive abilities, school enrolment, and educational attainment (highest grade reached at school). RESULTS: There was no significant overall intervention effect on cognitive abilities, but there was a significant interaction between intervention group and the duration of post-trial prophylaxis (p = 0.034), with cognitive ability somewhat higher in the intervention group among children who received no post-trial prophylaxis (treatment effect = 0.2 standard deviations [SD], 95% confidence interval [CI] -0.03 to 0.5) and among children who received less than 1 y of post-trial prophylaxis (treatment effect = 0.4 SD, 95% CI 0.1 to 0.8). The intervention group had higher educational attainment by 0.52 grades (95% CI = -0.041 to 1.089; p = 0.069). School enrolment was similar in the two groups. CONCLUSIONS: The results are suggestive of a long-term effect of malaria prophylaxis on cognitive function and educational attainment, but confirmatory studies are needed.

Journal Article↗
PubMed2006

Nasopharyngeal carriage of Streptococcus pneumoniae in Gambian villagers.

BACKGROUND: To prepare for the introduction of a pneumococcal conjugate vaccine of restricted valency, we studied the nasopharyngeal carriage of Streptococcus pneumoniae in Gambian villagers. METHODS: A cross-sectional survey was conducted in 21 villages after a census. We recorded demographic characteristics, information on medical history, and data on possible risk factors for carriage from subjects. We collected a nasopharyngeal swab specimen from each subject for isolation and serotyping of S. pneumoniae and for antibiotic susceptibility testing. RESULTS: The prevalence of S. pneumoniae carriage among 2872 villagers was 72%. It was highest among infants (i.e., children aged <1 year; 97%); the rate was 93% among babies aged <1 month and decreased with increasing age (P<.001). Prevalence of carriage was linked to proximity to another village. Sixty-three percent of isolates recovered from children aged <5 years were covered by the 7-valent vaccine or were of a vaccine-related serotype, compared with 43% of isolates overall. Forty-three isolates (14.3%) tested were initially penicillin resistant; none had high-level resistance, and 4 had intermediate resistance. The rates of resistance to other antibiotics were as follows: trimethoprim-sulfamethoxazole, 39%; tetracycline, 32.3%; chloramphenicol, 6.3%; cefotaxime, 0.3%; and erythromycin, 0%. The rates were highest for isolates of vaccine serotypes. CONCLUSIONS: Pneumococcal carriage rates among Gambian villagers are very high. A pneumococcal conjugate vaccine of restricted valency should reduce the pool of antibiotic-resistant pneumococci. The large reservoir of pneumococci of nonvaccine serotypes will require close monitoring when the vaccine is introduced.

Adolescent↗
PubMed2006

Response and non-response to a quality-of-life question on sexual life: a case study of the simple mean imputation method.

We investigated the non-response rates to the question "I am satisfied with my sex life" in the Functional Assessment of Cancer Therapy-General questionnaire in Chinese (n = 769), Malay (n = 41) and Indian (n = 33) patients in Singapore, a multi-ethnic society whose residents are said to have a conservative sexual attitude. Non-response rates to the question were 44%, 22% and 24% in the three groups respectively. The rates were much higher than that reported previously in a US study (7%) and used in the associated simulation study of the simple mean imputation method. We further examined the Chinese respondents in detail. The odds of non-response and the scores among the responders were associated with several demographic and clinical characteristics. Using the checklist proposed by Fayers et al. [Stat Med 1998; 17: 679-696] to assess the data patterns, we found that the application of the simple mean imputation is questionable. We employed an alternative (multiple) imputation procedure that took into account covariates that predicted the odds of non-response and the observed response scores. We compared the analytic results based on different approaches to handling missing values, and found that analysis based on the simple mean imputation gave results similar to that based on multiply imputed data even in this quite extreme example.

Asia, Southeastern↗
PubMed2006

Quick assessment of hopelessness: a cross-sectional study.

BACKGROUND: Lengthy questionnaires reduce data quality and impose a burden on respondents. Previous researchers proposed that a single item ("My future seems dark to me") and a 4-item component of the Beck's Hopelessness Scale (BHS) can summarise most of the information the BHS provides. There is no clear indication of what BHS cutoff values are useful in identifying people with suicide tendency. METHODS: In a population-based study of Chinese people aged between 15 and 59 in Hong Kong, the Chinese version of the BHS and the Centre for Epidemiologic Studies--Depression scale were administered by trained interviewers and suicidal ideation and suicidal attempts were self-reported. Receiver operating characteristics curve analysis and regression analysis were used to compare the performance of the BHS and its components in identifying people with suicidality and depression. Smoothed level of suicidal tendency was assessed in relation to scores on the BHS and its component to identify thresholds. RESULTS: It is found that the 4-item component and, to a lesser extent, the single item of the BHS perform in ways similar to the BHS. There are non-linear relationship between suicidality and scores on the BHS and the 4-item component; cutoff values identified accordingly have sensitivity and specificity of about 65%. CONCLUSION: The 4-item component is a useful alternative to the BHS. Shortening of psycho-social measurement scales should be considered in order to reduce burden on patients or respondents and to improve response rate.

Adolescent↗
PubMed2006

Suicidal ideation and suicidal attempts in a population-based study of Chinese people: risk attributable to hopelessness, depression, and social factors.

BACKGROUND: The population attributable fraction of hopelessness, depression and other risk factors for suicidal ideation and suicidal attempts in Asian population is unknown. Social support is often said to be a buffer against the effect of hopelessness and depression. METHODS: Suicidal ideation, suicidal attempts as well as demographic and psychometric data were delineated in a random and representative population sample of 2,219 Chinese people in Hong Kong. The population attributable fraction was used to determine the contribution of hopelessness, depression and other risk factors to suicidal ideation and attempts. RESULTS: Multivariate modelling shows that about 40% of suicidal ideation and attempts was attributable to depression and about 20% was attributable to hopelessness. Drug abuse and marital dissolution were also significant contributors to suicidality. The impact of hopelessness and depression was not affected by social support. LIMITATIONS: Suicidality was self-reported. CONCLUSIONS: Suicidal ideation and suicidal attempts were to a large extent attributable to depression and hopelessness, and, to a lesser extent, drug abuse and marital dissolution. Social support appeared to play little role as a buffer.

Adolescent↗
PubMed2006

Quality of life scores differed according to mode of administration in a review of three major oncology questionnaires.

OBJECTIVE: To assess whether scores on the three major quality-of-life questionnaires in oncology (FACT-G, FLIC, and EORTC QLQ-C30) are associated with modes of administration in a realistic clinical research setting. STUDY DESIGN AND SETTING: A heterogeneous sample of 1,265 cancer patients was recruited in Singapore. About one-fourth of the patients chose to have the interview administered by research staff; the rest self-completed the questionnaires. Multiple regression was used to adjust for differences in demographic and clinical characteristics between patients. An equivalence margin was defined as 0.25 standard deviations. RESULTS: Apart from one exception (the EORTC QLQ-C30 global functioning scale), all scales showed higher mean values in patients who were interviewed than patients who self-administered the questionnaires. For the physical and functional well-being scales of FACT-G and the physical and social functioning scales of EORTC QLQ-C30, the differences were small and the confidence intervals fell totally within the equivalence zone. The emotional well-being score of the FACT-G was different across modes of administration and the confidence interval fell outside the equivalence zones. There was no interaction between modes of administration and respondents' education level. CONCLUSION: The physical aspect of quality-of-life is not sensitive to interviewer administration but the psychological aspect is. Statistical adjustment for some scales is recommended.

Adult↗
PubMed2006

Epidemiologic and clinical characteristics of community-acquired invasive bacterial infections in children aged 2-29 months in The Gambia.

BACKGROUND: The incidence of community-acquired bacteremia (CAB) in Africa is several-fold higher than in industrialized countries. We report here the incidence of invasive bacterial infections in rural Gambia and compare the clinical characteristics of children with pneumococcal infection with those of children with extraintestinal nontyphoidal salmonella infection (NTS) or other bacterial infections. METHODS: As part of a pneumococcal conjugate vaccine trial, we investigated children aged 2-29 months who presented with signs suggestive of invasive bacterial infections. RESULTS: The incidence of invasive bacterial infections in all subjects was 1009 (95% CI, 903-1124) cases per 100,000 person-years. It was 1108 (95% CI, 953-1282) among children who had not received pneumococcal conjugate vaccine. Incidence decreased with increasing age but remained relatively high in 24- to 29-month-olds for pneumococcal infections. Pneumococcal infection was more frequent than NTS infections in the hot dry season. Respiratory symptoms and signs, consolidation on chest radiograph, and a primary diagnosis of pneumonia were more frequent in children with pneumococcal infection than in those with NTS or other infections. Diarrhea, laboratory evidence of malaria infection, and a primary diagnosis of malaria were more common in children with NTS infections. CONCLUSIONS: Bacterial infections continue to cause significant morbidity in rural Africa. Although vaccines could greatly reduce the pneumococcal burden, a high index of suspicion and appropriate use of antimicrobials are needed to manage other causes of invasive bacterial infections.

Bacterial Infections↗
PubMed2006

Semiparametric analysis of zero-inflated count data.

Medical and public health research often involve the analysis of count data that exhibit a substantially large proportion of zeros, such as the number of heart attacks and the number of days of missed primary activities in a given period. A zero-inflated Poisson regression model, which hypothesizes a two-point heterogeneity in the population characterized by a binary random effect, is generally used to model such data. Subjects are broadly categorized into the low-risk group leading to structural zero counts and high-risk (or normal) group so that the counts can be modeled by a Poisson regression model. The main aim is to identify the explanatory variables that have significant effects on (i) the probability that the subject is from the low-risk group by means of a logistic regression formulation; and (ii) the magnitude of the counts, given that the subject is from the high-risk group by means of a Poisson regression where the effects of the covariates are assumed to be linearly related to the natural logarithm of the mean of the counts. In this article we consider a semiparametric zero-inflated Poisson regression model that postulates a possibly nonlinear relationship between the natural logarithm of the mean of the counts and a particular covariate. A sieve maximum likelihood estimation method is proposed. Asymptotic properties of the proposed sieve maximum likelihood estimators are discussed. Under some mild conditions, the estimators are shown to be asymptotically efficient and normally distributed. Simulation studies were carried out to investigate the performance of the proposed method. For illustration purpose, the method is applied to a data set from a public health survey conducted in Indonesia where the variable of interest is the number of days of missed primary activities due to illness in a 4-week period.

Biometry↗
PubMed2006

Uptake of workplace HIV counselling and testing: a cluster-randomised trial in Zimbabwe.

BACKGROUND: HIV counselling and testing is a key component of both HIV care and HIV prevention, but uptake is currently low. We investigated the impact of rapid HIV testing at the workplace on uptake of voluntary counselling and testing (VCT). METHODS AND FINDINGS: The study was a cluster-randomised trial of two VCT strategies, with business occupational health clinics as the unit of randomisation. VCT was directly offered to all employees, followed by 2 y of open access to VCT and basic HIV care. Businesses were randomised to either on-site rapid HIV testing at their occupational clinic (11 businesses) or to vouchers for off-site VCT at a chain of free-standing centres also using rapid tests (11 businesses). Baseline anonymised HIV serology was requested from all employees. HIV prevalence was 19.8% and 18.4%, respectively, at businesses randomised to on-site and off-site VCT. In total, 1,957 of 3,950 employees at clinics randomised to on-site testing had VCT (mean uptake by site 51.1%) compared to 586 of 3,532 employees taking vouchers at clinics randomised to off-site testing (mean uptake by site 19.2%). The risk ratio for on-site VCT compared to voucher uptake was 2.8 (95% confidence interval 1.8 to 3.8) after adjustment for potential confounders. Only 125 employees (mean uptake by site 4.3%) reported using their voucher, so that the true adjusted risk ratio for on-site compared to off-site VCT may have been as high as 12.5 (95% confidence interval 8.2 to 16.8). CONCLUSIONS: High-impact VCT strategies are urgently needed to maximise HIV prevention and access to care in Africa. VCT at the workplace offers the potential for high uptake when offered on-site and linked to basic HIV care. Convenience and accessibility appear to have critical roles in the acceptability of community-based VCT.

AIDS Serodiagnosis↗
PubMed2006

Developing health-related quality-of-life instruments for use in Asia: the issues.

About half of the world's population live in Asia. Mandarin (the official language of China), Hindi and Japanese are among the ten languages spoken by the largest number of primary speakers. The numbers of Tamil and Malay speakers are expected to grow rapidly in the next few decades. Most health-related quality-of-life (HR-QOL) instruments currently used in Asia are translations and/or adaptations of instruments developed in North America and Western Europe. We illustrate and discuss several major issues in the development of HR-QOL instruments for use in Asia. We have seen insufficient quality in translation and semantic equivalence, which is not a uniquely Asian problem. This problem will be alleviated by putting recently proposed guidelines for translation and adaptation of patient-reported outcomes into practice and formally conducting equivalence studies. For copyright or other reasons it is rare to see major adaptations, such as exclusion of a domain in the original instrument or inclusion of a new domain, made to existing instruments. Evidence is limited and mixed as to whether there are differences in the concepts of HR-QOL between Asian and North American/Western European cultures that are important enough to justify such major adaptations, or the development of indigenous instruments, as opposed to the translation/adaptation of existing instruments. There are substantial cultural differences concerning what questions are appropriate to ask and answer. Many HR-QOL instruments are designed for self-completion. This mode of administration is often not feasible in Asia because of low literacy rates and the presence of many different regional languages. Alternative administration methods and analytic strategies that allow for pooling data collected by different modes are needed. The availability of HR-QOL instruments in various Asian countries seems to reflect the status of economic development of the countries rather than their disease burden. For instance, many important HR-QOL instruments are available in Japanese but not in Hindi or Tamil.

Asia↗
PubMed2005

Meta-analysis of the influence of MDR1 C3435T polymorphism on digoxin pharmacokinetics and MDR1 gene expression.

AIMS: Studies revealing conflicting results of the functional significance of MDR1 exon 26 C3435T SNP on the disposition of digoxin in different ethnic groups led us to perform a meta-analysis on published data investigating the influence of C3435T SNP on the pharmacokinetics of digoxin and the expression of MDR1. METHODS: Meta-analysis was performed on data from published studies investigating the influence of MDR1 C3435T SNP on digoxin pharmacokinetics, as well as MDR1 expression in Caucasian and Japanese populations. The following outcomes were included: exposures to digoxin measured by area under the concentration-time curve and maximum concentration, the mean intestinal MDR1 mRNA expression and P-gp expression in the absence of digoxin administration. RESULTS: The overall results of the meta-analysis in Caucasian and Japanese subjects suggested no major influence of the C3435T SNP on exposure levels of digoxin as determined by AUC(0-4 h) or AUC(0-24 h) although C(max) values for digoxin were lower in wild-type (CC) subjects compared with subjects harbouring TT genotypes. Subgroup analysis by ethnic populations showed the oral availability of digoxin to be lower in wild-type Caucasian populations compared with wild-type Japanese subjects. No causal relationships were detected between the C3435T SNP and MDR1 mRNA or protein expression. CONCLUSIONS: Our meta-analysis of available studies indicates that the synonymous MDR1 C3435T SNP does not affect the pharmacokinetics of digoxin and the expression of MDR1 mRNA. Future studies should focus on the impact of MDR1 haplotypes on the pharmacokinetics of MDR1 substrates rather than the C3435T SNP alone.

Administration, Oral↗