Biomedical subjects

Mei-Cheng Wang

Publications and source records attributed to Mei-Cheng Wang.

12 recordsLinked to original sources

PubMed2006

Do urban parents' interests in safety topics match their children's injury risks?

OBJECTIVE: To assess childhood injury risk and parents' injury interests, and the association between the two. METHOD: A cross-sectional computer and telephone survey was conducted as part of a randomized controlled trial. The authors enrolled parents of children being seen at an urban pediatric primary care practice and measured selected injury knowledge, beliefs and safety practices. Parents were asked to select two of four topics of interest and recommendations regarding them were included in a computer-tailored report. RESULTS: Participants (N = 105) were assessed as being at risk for all four areas: poisoning (88%), fires (85%), falls (55%), and car crashes (18%). Parents were interested in poisoning (81%) and car crashes (49%); their interests were unrelated to child's assessed risk. CONCLUSION: Soliciting parents' interests prior to counseling may help to identify priority areas for counseling as well as dispel myths and unfounded fears regarding childhood injury risks.

Adult↗

PubMed2005

Marginal analysis for clustered failure time data.

Clustered failure time data are commonly encountered in biomedical research where the study subjects from the same cluster (e.g., family) share the common genetic and/or environmental factors such that the failure times within the same cluster are correlated. Two approaches that are commonly used to account for the intra-cluster association are frailty models and marginal models. In this paper, we study the marginal proportional hazards model, where the structure of dependence between individuals within a cluster is unspecified. An estimation procedure is developed based on a pseudo-likelihood approach, and a risk set sampling method is proposed for the formulation of the pseudo-likelihood. The asymptotic properties of the proposed estimators are studied, and the related issues regarding the statistical efficiencies are discussed. The performances of the proposed estimator are demonstrated by the simulation studies. A data example from a child vitamin A supplementation trial in Nepal (Nepal Nutrition Intervention Project-Sarlahi, or NNIPS) is used to illustrate this methodology.

Cluster Analysis↗

PubMed2005

Random weighted bootstrap method for recurrent events with informative censoring.

Using the data from the AIDS Link to Intravenous Experiences cohort study as an example, an informative censoring model was used to characterize the repeated hospitalization process of a group of patients. Under the informative censoring assumption, the estimators of the baseline rate function and the regression parameters were shown to be related to a latent variable. Hence, it becomes impractical to directly estimate the unknown quantities in the moments of the estimators for the bandwidth selection of a smoothing estimator and the construction of confidence intervals, which are respectively based on the asymptotic mean squared errors and the asymptotic distributions of the estimators. To overcome these difficulties, we develop a random weighted bootstrap procedure to select appropriate bandwidths and to construct approximated confidence intervals. One can see that our method is simple and faster to implement from a practical point of view, and is at least as accurate as other bootstrap methods. In this article, it is shown that the proposed method is useful through the performance of a Monte Carlo simulation. An application of our procedure is also illustrated by a recurrent event sample of intravenous drug users for inpatient cares over time.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Nonparametric estimation of the bivariate recurrence time distribution.

This article considers statistical models in which two different types of events, such as the diagnosis of a disease and the remission of the disease, occur alternately over time and are observed subject to right censoring. We propose nonparametric estimators for the joint distribution of bivariate recurrence times and the marginal distribution of the first recurrence time. In general, the marginal distribution of the second recurrence time cannot be estimated due to an identifiability problem, but a conditional distribution of the second recurrence time can be estimated non-parametrically. In the literature, statistical methods have been developed to estimate the joint distribution of bivariate recurrence times based on data on the first pair of censored bivariate recurrence times. These methods are inefficient in the model considered here because recurrence times of higher orders are not used. Asymptotic properties of the proposed estimators are established. Numerical studies demonstrate the estimators perform well with practical sample sizes. We apply the proposed method to the South Verona, Italy, psychiatric case register (PCR) data set for illustration of the methods and theory.

Algorithms↗

PubMed2004

Semiparametric regression analysis on longitudinal pattern of recurrent gap times.

In longitudinal studies, individual subject may experience recurrent events of the same type over a relatively long period of time. The longitudinal pattern of gaps between successive recurrent events is often of great research interest. In this article, the probability structure of the recurrent gap times is first explored in the presence of censoring. According to the discovered structure, we introduce the stratified proportional reverse-time hazards models with unspecified baseline functions to accommodate individual heterogeneity, when the longitudinal pattern parameter is of main interest. Inference procedures are proposed and studied by way of proper riskset construction. The proposed methodology is demonstrated by the Monte Carlo simulations and an application to a well-known Denmark schizophrenia cohort study data set.

Age of Onset↗

PubMed2004

Generation and characterization of DNA vaccines targeting the nucleocapsid protein of severe acute respiratory syndrome coronavirus.

Severe acute respiratory syndrome (SARS) is a serious threat to public health and the economy on a global scale. The SARS coronavirus (SARS-CoV) has been identified as the etiological agent for SARS. Thus, vaccination against SARS-CoV may represent an effective approach to controlling SARS. DNA vaccines are an attractive approach for SARS vaccine development, as they offer many advantages over conventional vaccines, including stability, simplicity, and safety. Our investigators have previously shown that DNA vaccination with antigen linked to calreticulin (CRT) dramatically enhances major histocompatibility complex class I presentation of linked antigen to CD8(+) T cells. In this study, we have employed this CRT-based enhancement strategy to create effective DNA vaccines using SARS-CoV nucleocapsid (N) protein as a target antigen. Vaccination with naked CRT/N DNA generated the most potent N-specific humoral and T-cell-mediated immune responses in vaccinated C57BL/6 mice among all of the DNA constructs tested. Furthermore, mice vaccinated with CRT/N DNA were capable of significantly reducing the titer of challenging vaccinia virus expressing the N protein of the SARS virus. These results show that a DNA vaccine encoding CRT linked to a SARS-CoV antigen is capable of generating strong N-specific humoral and cellular immunity and may potentially be useful for control of infection with SARS-CoV.

Amino Acid Sequence↗

PubMed2003

Longitudinal care improves disclosure of psychosocial information.

BACKGROUND: While longitudinal primary care is thought to promote patient rapport and trust, it is not known if longitudinality helps overcome barriers to communication that may occur when the patient and physician are of different ethnicities and/or sexes. OBJECTIVE: To examine if longitudinal pediatric care ameliorates disparities in parent disclosure of psychosocial information associated with ethnic and gender discordance between parent and physician. DESIGN: Longitudinal, observational study of parent-physician interaction at early visits and over the course of 1 year. PARTICIPANTS: Parents (90% African American and 10% white mothers or female guardians) and their infant's assigned primary care physician (white first- and second-year pediatric residents). MAIN OUTCOME MEASURE: Parents' psychosocial information giving measured by the Roter Interaction Analysis System. RESULTS: Sex- and race-related barriers to disclosure of psychosocial information were evident early in the parent-physician relationship. At early visits, African American mothers made 26% fewer psychosocial statements than white mothers; this discrepancy was not affected by physician sex. At early visits, white mothers made twice as many psychosocial statements when seeing white female compared with white male physicians. CONCLUSIONS: Patient-centeredness is an important factor promoting psychosocial information giving for African American and white mothers, regardless of physician sex. Longitudinal relationships facilitate mothers' disclosure to physicians of a different ethnicity or sex, but only if physicians remain patient-centered.

Adolescent↗

PubMed2003

The role of Medicaid HMO enrollment in the longitudinal utilization of medical care services in a cohort of injecting drug users in Baltimore, Maryland.

Although injecting drug users (IDUs) are highly dependent on Medicaid, the literature has not explored the effect of Medicaid HMO enrollment on medical care utilization. This longitudinal analysis compares 6-month utilization levels of IDUs in Medicaid HMOs with those of other Medicaid-enrolled IDUs and IDUs in other insurance arrangements. The analysis includes 1064 participants from the AIDS Link to Intravenous Experience (ALIVE) study, a natural history study of HIV infection in a community-based sample of IDUs in Baltimore, Maryland. A generalized linear modeling approach was used to examine self-reported inpatient admissions, ER visits, and ambulatory care visits from January 1995 through June 1997. Non-HMO Medicaid beneficiaries had more inpatient admissions and ambulatory care visits than Medicaid HMO enrollees. These findings suggest that HMO enrollment has been effective in lowering utilization among IDUs in Medicaid, but it is unclear whether utilization differences are the result of inappropriate utilization or access issues.

Adult↗

PubMed2002

Non-parametric methods for recurrent event data with informative and non-informative censorings.

Recurrent event data are commonly encountered in health-related longitudinal studies. In this paper time-to-events models for recurrent event data are studied with non-informative and informative censorings. In statistical literature, the risk set methods have been confirmed to serve as an appropriate and efficient approach for analysing recurrent event data when censoring is non-informative. This approach produces biased results, however, when censoring is informative for the time-to-events outcome data. We compare the risk set methods with alternative non-parametric approaches which are robust subject to informative censoring. In particular, non-parametric procedures for the estimation of the cumulative occurrence rate function (CORF) and the occurrence rate function (ORF) are discussed in detail. Simulation and an analysis of data from the AIDS Link to Intravenous Experiences Cohort Study is presented.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Effects of improved access to safety counseling, products, and home visits on parents' safety practices: results of a randomized trial.

OBJECTIVE: To present the results of an intervention trial to enhance parents' home-safety practices through pediatric safety counseling, home visits, and an on-site children's safety center where parents receive personalized education and can purchase reduced-cost products. DESIGN: Pediatricians were randomized to a standard- or an enhanced-intervention group. Parents of their patients were enrolled when the patient was 6 months or younger and observed until 12 to 18 months of age. SETTING: A hospital-based pediatric resident continuity clinic that serves families living in low-income, inner-city neighborhoods. PARTICIPANTS: First- and second-year pediatric residents and their patient-parent dyads. INTERVENTIONS: Parents in the standard-intervention group received safety counseling and referral to the children's safety center from their pediatrician. Parents in the enhanced-intervention group received the standard services plus a home-safety visit by a community health worker. OUTCOMES: Home observers assessed the following safety practices: reduction of hot-water temperature, poison storage, and presence of smoke alarms, safety gates for stairs, and ipecac syrup. RESULTS: The prevalence of safety practices ranged from 11% of parents who stored poisons safely to 82% who had a working smoke alarm. No significant differences in safety practices were found between study groups. However, families who visited the children's safety center compared with those who did not had a significantly greater number of safety practices (34% vs 17% had > or 3). CONCLUSIONS: Home visiting was not effective in improving parents' safety practices. Counseling coupled with convenient access to reduced-cost products appears to be an effective strategy for promoting children's home safety.

Adult↗

PubMed2002

Mechanisms behind the failure of residents' longitudinal primary care to promote disclosure and discussion of psychosocial issues.

CONTEXT: Longitudinality (care by a single physician over time) and continuity (receipt of most care from a single physician) are believed to enhance patient-physician relationships and facilitate disclosure of emotional distress, but some studies suggest this potential goes unrealized. OBJECTIVES: To determine whether care in a pediatric residents' continuity clinic promotes, over time, increased discussion, disclosure, and detection of parents' social and emotional distress and to understand physicians' communication behaviors underlying changes with time. DESIGN: Longitudinal, observational study of parent-physician interaction over the course of 1 year. PARTICIPANTS: One hundred ninety parents (90% African American) and their infants' primary care physicians (31 [4 Asians and 27 whites] first- and second-year pediatric residents). MAIN OUTCOME MEASURES: Frequency with which parents and physicians raised topics related to parental mood and family or social functioning; proportion of distressed parents discussing mood or functioning; and physicians' detection of parent distress. RESULTS: Physician initiation of psychosocial topics fell in the course of longitudinal relationships (odds of initiation in visits > or =6 vs odds of initiation in visits 1-5 = 0.46 [95% confidence limits, 0.31%, 0.67%]); parent initiation did not change over time nor was it increased by greater levels of continuity. Length of relationship was not associated with increased physician detection of parental distress or with increased rates of disclosure by distressed parents. Physicians' positively framed leading questions, and their avoidant responses to prior parental disclosures were significantly associated with decreased odds of problem disclosure. In contrast, visits in which parents or physicians raised psychosocial topics were characterized, on average, by 40% higher levels of physicians' "patient-centeredness" (increases of about 100 utterances per visit [95% confidence limits, 65.7%, 133.9%]). CONCLUSIONS: Longitudinal relationships between residents and patients may not be sufficient to promote the discussion, disclosure, and detection of psychosocial issues. Training in communication skills may help residents achieve the potential and goals of longitudinal care.

Adult↗

PubMed2002

Cohort case-control design and analysis for clustered failure-time data.

Cohort case-control design is an efficient and economical design to study risk factors for disease incidence or mortality in a large cohort. In the last few decades, a variety of cohort case-control designs have been developed and theoretically justified. These designs have been exclusively applied to the analysis of univariate failure-time data. In this work, a cohort case-control design adapted to multivariate failure-time data is developed. A risk set sampling method is proposed to sample controls from nonfailures in a large cohort for each case matched by failure time. This method leads to a pseudolikelihood approach for the estimation of regression parameters in the marginal proportional hazards model (Cox, 1972, Journal of the Royal Statistical Society, Series B 34, 187-220), where the correlation structure between individuals within a cluster is left unspecified. The performance of the proposed estimator is demonstrated by simulation studies. A bootstrap method is proposed for inferential purposes. This methodology is illustrated by a data example from a child vitamin A supplementation trial in Nepal (Nepal Nutrition Intervention Project-Sarlahi, or NNIPS).

Case-Control Studies↗