Abstract:
BACKGROUND:A zero-inflated continuous outcome is characterized by occurrence of "excess" zeros that more than a single distribution can explain, with the positive observations forming a skewed distribution. Mixture models are employed for regression analysis of zero-inflated data. Moreover, for repeated measures zero-inflated data the clustering structure should also be modeled for an adequate analysis. METHODS:Diary of Asthma and Viral Infections Study (DAVIS) was a one year (2004) cohort study conducted at McMaster University to monitor viral infection and respiratory symptoms in children aged 5-11 years with and without asthma. Respiratory symptoms were recorded daily using either an Internet or paper-based diary. Changes in symptoms were assessed by study staff and led to collection of nasal fluid specimens for virological testing. The study objectives included investigating the response of respiratory symptoms to respiratory viral infection in children with and without asthma over a one year period. Due to sparse data daily respiratory symptom scores were aggregated into weekly average scores. More than 70% of the weekly average scores were zero, with the positive scores forming a skewed distribution. We propose a random effects probit/log-skew-normal mixture model to analyze the DAVIS data. The model parameters were estimated using a maximum marginal likelihood approach. A simulation study was conducted to assess the performance of the proposed mixture model if the underlying distribution of the positive response is different from log-skew normal. RESULTS:Viral infection status was highly significant in both probit and log-skew normal model components respectively. The probability of being symptom free was much lower for the week a child was viral positive relative to the week she/he was viral negative. The severity of the symptoms was also greater for the week a child was viral positive. The probability of being symptom free was smaller for asthmatics relative to non-asthmatics throughout the year, whereas there was no difference in the severity of the symptoms between the two groups. CONCLUSIONS:A positive association was observed between viral infection status and both the probability of experiencing any respiratory symptoms, and their severity during the year. For DAVIS data the random effects probit -log skew normal model fits significantly better than the random effects probit -log normal model, endorsing our parametric choice for the model. The simulation study indicates that our proposed model seems to be robust to misspecification of the distribution of the positive skewed response.
journal_name
BMC Med Res Methodoljournal_title
BMC medical research methodologyauthors
Mahmud S,Lou WW,Johnston NWdoi
10.1186/1471-2288-10-55subject
Has Abstractpub_date
2010-06-14 00:00:00pages
55issn
1471-2288pii
1471-2288-10-55journal_volume
10pub_type
杂志文章abstract:BACKGROUND:The BSI-18 contains the three six-item scales somatization, depression, and anxiety as well as the Global Severity Index (GSI), including all 18 items. The BSI-18 is the latest and shortest of the multidimensional versions of the Symptom-Checklist 90-R, but its psychometric properties have not been sufficien...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-016-0283-3
更新日期:2017-01-26 00:00:00
abstract:BACKGROUND:Longitudinal studies using data collected as part of usual care risk providing biased results if visit times are related to the outcome of interest. Statistical methods for mitigating this bias are available but rarely used. This lack of use could be attributed to a lack of need or to a lack of awareness of ...
journal_title:BMC medical research methodology
pub_type: 杂志文章,评审
doi:10.1186/s12874-017-0418-1
更新日期:2017-09-06 00:00:00
abstract:BACKGROUND:Evidence mapping describes the quantity, design and characteristics of research in broad topic areas, in contrast to systematic reviews, which usually address narrowly-focused research questions. The breadth of evidence mapping helps to identify evidence gaps, and may guide future research efforts. The Globa...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-11-92
更新日期:2011-06-17 00:00:00
abstract:BACKGROUND:Small number of clusters and large variation of cluster sizes commonly exist in cluster-randomized trials (CRTs) and are often the critical factors affecting the validity and efficiency of statistical analyses. F tests are commonly used in the generalized linear mixed model (GLMM) to test intervention effect...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-015-0026-x
更新日期:2015-04-23 00:00:00
abstract:BACKGROUND:This paper discusses whether baseline demographic, socio-economic, health variables, length of follow-up and method of contacting the participants predict non-response to the invitation for a second assessment of lifestyle factors and body weight in the European multi-center EPIC-PANACEA study. METHODS:Over...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-12-148
更新日期:2012-09-24 00:00:00
abstract:BACKGROUND:Cancer relapses may be useful to predict the risk of death. To take into account relapse information, the Landmark approach is popular. As an alternative, we propose the joint frailty model for a recurrent event and a terminal event to derive dynamic predictions of the risk of death. METHODS:The proposed pr...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-015-0018-x
更新日期:2015-04-01 00:00:00
abstract:BACKGROUND:To assess cross-cultural validity between Dutch and English versions of the FVQ_CYP, a patient-reported outcome measure developed in the United Kingdom (UK) for children and adolescents with (severe) visual impairment or blindness (VI for brevity) to measure functional vision. METHODS:The 36-item FVQ_CYP wa...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-019-0875-9
更新日期:2019-12-03 00:00:00
abstract:BACKGROUND:With the increasing implementation of web-based, mobile health interventions in clinical trials, it is crucial for researchers to address the security and privacy concerns of patient information according to high ethical standards. The full process of meeting these standards is often made more complicated du...
journal_title:BMC medical research methodology
pub_type: 社论
doi:10.1186/s12874-017-0324-6
更新日期:2017-03-17 00:00:00
abstract:BACKGROUND:With the increased empirical interest in the positive significance of improving nurses' sense of professional benefits, there is a requirement for measures of nurses' perceived professional benefit (NPPB). Our objective was to develop and psychometrically test a brief Nurses' Perceived Professional Benefit Q...
journal_title:BMC medical research methodology
pub_type: 杂志文章,多中心研究
doi:10.1186/s12874-020-0908-4
更新日期:2020-01-30 00:00:00
abstract:BACKGROUND:When discussing results medical research articles often tear substantive and statistical (methodical) contributions apart, just as if both were independent. Consequently, reasoning on bias tends to be vague, unclear and superficial. This can lead to over-generalized, too narrow and misleading conclusions, es...
journal_title:BMC medical research methodology
pub_type: 杂志文章,评审
doi:10.1186/s12874-018-0490-1
更新日期:2018-04-17 00:00:00
abstract:BACKGROUND:The aim was to describe a strategy for recruitment of healthy volunteers (HV) to a randomized trial that assessed the efficacy of different telephone techniques to assist HV in performing cardiac massage for vital emergency. Participation in the randomized trial was not financially compensated, however HV we...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-15-2
更新日期:2015-01-05 00:00:00
abstract:BACKGROUND:Primary care databases are a major source of data for epidemiological and health services research. However, most studies are based on coded information, ignoring information stored in free text. Using the early presentation of rheumatoid arthritis (RA) as an exemplar, our objective was to estimate the exten...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-13-105
更新日期:2013-08-21 00:00:00
abstract:BACKGROUND:Compelled by the intuitive appeal of predicting each individual patient's risk of an outcome, there is a growing interest in risk prediction models. While the statistical methods used to build prediction models are increasingly well understood, the literature offers little insight to researchers seeking to g...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-016-0223-2
更新日期:2016-09-21 00:00:00
abstract:BACKGROUND:In spite of efforts to employ risk-based strategies to increase monitoring efficiency in the academic setting, empirical evidence on their effectiveness remains sparse. This mixed-methods study aimed to evaluate the risk-based on-site monitoring approach currently followed at our academic institution. METHO...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-017-0308-6
更新日期:2017-02-14 00:00:00
abstract:BACKGROUND:Sickness absence (SA) is an important social, economic and public health issue. Identifying and understanding the determinants, whether biological, regulatory or, health services-related, of variability in SA duration is essential for better management of SA. The conditional frailty model (CFM) is useful whe...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-13-114
更新日期:2013-09-16 00:00:00
abstract:BACKGROUND:The Community Reintegration of Service Members (CRIS) is a new measure of community reintegration developed to measure veteran's participation in life roles. It consists of three sub-scales: Extent of Participation (Extent), Perceived Limitations with Participation (Perceived), and Satisfaction with Particip...
journal_title:BMC medical research methodology
pub_type: 杂志文章,随机对照试验
doi:10.1186/1471-2288-11-98
更新日期:2011-06-25 00:00:00
abstract:BACKGROUND:Missing data present a challenge to many research projects. The problem is often pronounced in studies utilizing self-report scales, and literature addressing different strategies for dealing with missing data in such circumstances is scarce. The objective of this study was to compare six different imputatio...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-6-57
更新日期:2006-12-13 00:00:00
abstract:BACKGROUND:The intraclass correlation coefficient (ICC) is widely used in biomedical research to assess the reproducibility of measurements between raters, labs, technicians, or devices. For example, in an inter-rater reliability study, a high ICC value means that noise variability (between-raters and within-raters) is...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-14-121
更新日期:2014-11-22 00:00:00
abstract:BACKGROUND:Data on lifetime exposures are often self-reported in epidemiologic studies, sometimes many years after the relevant age. Validity of self-reported data is usually inferred from their agreement with measured values, but few studies directly quantify the likely effects of reporting errors in body size and rep...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-11-7
更新日期:2011-01-17 00:00:00
abstract:BACKGROUND:Defeat and entrapment have been shown to be of central relevance to the development of different disorders. However, it remains unclear whether they represent two distinct constructs or one overall latent variable. One reason for the unclarity is that traditional factor analytic techniques have trouble estim...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-018-0470-5
更新日期:2018-01-25 00:00:00
abstract:BACKGROUND:Self-administered questionnaires are becoming increasingly common in general practice. Much research has explored methods to increase response rates but comparatively few studies have explored the effect of questionnaire administration on reported answers. METHODS:The aim of this study was to determine the ...
journal_title:BMC medical research methodology
pub_type: 杂志文章,随机对照试验
doi:10.1186/1471-2288-8-42
更新日期:2008-06-27 00:00:00
abstract:BACKGROUND:Action research (AR) and randomized controlled trials (RCTs) are usually considered to be theoretically and practically incompatible. However, we argue that their respective strengths and weaknesses can be complementary. We illustrate our argument from a recent study assessing the effect of telemonitoring on...
journal_title:BMC medical research methodology
pub_type: 杂志文章,随机对照试验
doi:10.1186/s12874-016-0175-6
更新日期:2016-06-08 00:00:00
abstract:BACKGROUND:The "real" effect size of a medical therapy is constant over time. In contrast, the effect size reported in randomised controlled trials (RCTs) may change over time because the sum of all kinds of bias influencing the reported effectiveness is not necessarily constant. As this would affect the validity of me...
journal_title:BMC medical research methodology
pub_type: 杂志文章,meta分析
doi:10.1186/1471-2288-6-25
更新日期:2006-05-11 00:00:00
abstract:BACKGROUND:Systematic reviews (SRs) must be of high quality. The purpose of our research was to compare the methodological and reporting quality of original versus updated Cochrane SRs to determine whether updating had improved these two quality dimensions. METHODS:We identified updated Cochrane SRs published in issue...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-6-27
更新日期:2006-06-13 00:00:00
abstract:BACKGROUND:The International Cancer Benchmarking Partnership aims to study international differences in cancer survival and the possible causes. Participating countries are Australia, Canada, Norway, Sweden, Denmark and the UK and a particular focus area is differences in awareness and beliefs about cancer. In this con...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-017-0352-2
更新日期:2017-04-26 00:00:00
abstract:BACKGROUND:For practical reasons it is not easy to obtain fasting samples in large population health surveys. Non-fasting triglyceride (Tg) values are difficult to interpret. The authors compared the accuracy of statistically corrected non-fasting Tg values with true fasting values and estimated the misclassification o...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-11-63
更新日期:2011-05-10 00:00:00
abstract:BACKGROUND:The term 'inequities' refers to avoidable differences rooted in injustice. This review examined whether or not, and how, quantitative studies identifying inequalities in risk factors and health service utilization for asthma explicitly addressed underlying inequities. Asthma was chosen because recent decades...
journal_title:BMC medical research methodology
pub_type: 杂志文章,评审
doi:10.1186/1471-2288-11-104
更新日期:2011-07-12 00:00:00
abstract:BACKGROUND:Claims databases are generally considered inadequate for obesity research due to suboptimal capture of body mass index (BMI) measurements. This might not be true for bariatric surgery because of reimbursement requirements and changes in coding systems. We assessed the availability and validity of claims-base...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-020-01106-8
更新日期:2020-09-07 00:00:00
abstract:BACKGROUND:When multiple endpoints are of interest in evidence synthesis, a multivariate meta-analysis can jointly synthesise those endpoints and utilise their correlation. A multivariate random-effects meta-analysis must incorporate and estimate the between-study correlation (rhoB). METHODS:In this paper we assess ma...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/1471-2288-7-3
更新日期:2007-01-12 00:00:00
abstract:BACKGROUND:Various papers have addressed pros and cons of the stepped wedge cluster randomized trial design (SWD). However, some issues have not or only limitedly been addressed. Our aim was to provide a comprehensive overview of all merits and limitations of the SWD to assist researchers, reviewers and medical ethics ...
journal_title:BMC medical research methodology
pub_type: 杂志文章
doi:10.1186/s12874-015-0090-2
更新日期:2015-10-30 00:00:00