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Biomedical subjects

Martijn P F Berger

Publications and source records attributed to Martijn P F Berger.

14 recordsLinked to original sources
PubMed2007

Relative efficiency of unequal versus equal cluster sizes in cluster randomized and multicentre trials.

Cluster randomized and multicentre trials evaluate the effect of a treatment on persons nested within clusters, for instance, patients within clinics or pupils within schools. Optimal sample sizes at the cluster (centre) and person level have been derived under the restrictive assumption of equal sample sizes per cluster. This paper addresses the relative efficiency of unequal versus equal cluster sizes in case of cluster randomization and person randomization within clusters. Starting from maximum likelihood parameter estimation, the relative efficiency is investigated numerically for a range of cluster size distributions. An approximate formula is presented for computing the relative efficiency as a function of the mean and variance of cluster size and the intraclass correlation, which can be used for adjusting the sample size. The accuracy of this formula is checked against the numerical results and found to be quite good. It is concluded that the loss of efficiency due to variation of cluster sizes rarely exceeds 10 per cent and can be compensated by sampling 11 per cent more clusters.

Cluster Analysis↗
PubMed2006

Short-term effects of an educational intervention on physical restraint use: a cluster randomized trial.

BACKGROUND: Physical restraints are still frequently used in nursing home residents despite growing evidence for the ineffectiveness and negative consequences of these methods. Therefore, reduction in the use of physical restraints in psycho-geriatric nursing home residents is very important. The aim of this study was to investigate the short-term effects of an educational intervention on the use of physical restraints in psycho-geriatric nursing home residents. METHODS: A cluster randomized trial was applied to 5 psycho-geriatric nursing home wards (n = 167 residents with dementia). The wards were assigned at random to either educational intervention (3 wards) or control status (2 wards). The restraint status was observed and residents' characteristics, such as cognitive status, were determined by using the Minimum Data Set (MDS) at baseline and 1 month after intervention. RESULTS: Restraint use did not change significantly over time in the experimental group (55%-56%), compared to a significant increased use (P < 0.05) in the control group (56%-70%). The mean restraint intensity and mean multiple restraint use in residents increased in the control group but no changes were shown in the experimental group. Logistic regression analysis showed that residents in the control group were more likely to experience increased restraint use than residents in the experimental group. CONCLUSION: An educational programme for nurses combined with consultation with a nurse specialist did not decrease the use of physical restraints in psycho-geriatric nursing home residents in the short term. However, the residents in the control group experienced more restraint use during the study period compared to the residents in the experimental group. Whether the intervention will reduce restraint use in the long term could not be inferred from these results. Further research is necessary to gain insight into the long-term effects of this educational intervention.

Activities of Daily Living↗
PubMed2006

The psychometric quality and clinical usefulness of three pain assessment tools for elderly people with dementia.

In view of the need for valid, reliable, and clinically useful scales to assess pain in elderly people with dementia, this study evaluated the psychometric properties of translated versions of the PAINAD, PACSLAC, and DOLOPLUS-2 scales. In an observational study design, two raters simultaneously assessed the nursing home residents (n=128) for pain during influenza vaccination and care situations. The PACSLAC was valued as the most useful scale by nurses. Cronbach's alpha was high (>.80) for the total scale at T2 and T3 and adequate for the 'Facial expression' and 'Social/personality/mood' subscales. IC scores for the 'Activity/body movement' and 'Physiological indicators/eating/sleeping changes/vocal behaviors' subscales were low. It demonstrated good validity and reliability, although the scale should be further refined. This refinement should increase homogeneity. The PAINAD showed good psychometric qualities in terms of reliability, validity, and homogeneity (alpha ranged .69-.74 at T2 and T3) (except for the 'Breathing' item). The PAINAD scale had lower scores for clinical usefulness in this sample. The Dutch version of the DOLOPLUS-2 was considered more difficult to use but showed acceptable psychometric qualities in terms of the issues assessed, except for the 'psychosocial reactions' subscale. IC of the DOLOPLUS were adequate for the total scale (alpha ranged .74-.75) and almost all subscales (alpha ranged .58-.80). Findings of this study provide evidence of validity and reliability of the three pain assessment scales. Now that a pain scale is available, future studies also need to focus on its implementation in nursing practice.

Adult↗
PubMed2006

Pain in elderly people with severe dementia: a systematic review of behavioural pain assessment tools.

BACKGROUND: Pain is a common and major problem among nursing home residents. The prevalence of pain in elderly nursing home people is 40-80%, showing that they are at great risk of experiencing pain. Since assessment of pain is an important step towards the treatment of pain, there is a need for manageable, valid and reliable tools to assess pain in elderly people with dementia. METHODS: This systematic review identifies pain assessment scales for elderly people with severe dementia and evaluates the psychometric properties and clinical utility of these instruments. Relevant publications in English, German, French or Dutch, from 1988 to 2005, were identified by means of an extensive search strategy in Medline, Psychinfo and CINAHL, supplemented by screening citations and references. Quality judgement criteria were formulated and used to evaluate the psychometric aspects of the scales. RESULTS: Twenty-nine publications reporting on behavioural pain assessment instruments were selected for this review. Twelve observational pain assessment scales (DOLOPLUS2; ECPA; ECS; Observational Pain Behavior Tool; CNPI; PACSLAC; PAINAD; PADE; RaPID; Abbey Pain Scale; NOPPAIN; Pain assessment scale for use with cognitively impaired adults) were identified. Findings indicate that most observational scales are under development and show moderate psychometric qualities. CONCLUSION: Based on the psychometric qualities and criteria regarding sensitivity and clinical utility, we conclude that PACSLAC and DOLOPLUS2 are the most appropriate scales currently available. Further research should focus on improving these scales by further testing their validity, reliability and clinical utility.

Aged↗
PubMed2006

Massage to prevent pressure ulcers: knowledge, beliefs and practice. A cross-sectional study among nurses in the Netherlands in 1991 and 2003.

BACKGROUND: Pressure ulcers are a major problem in all areas of health care in the Netherlands. National guidelines for the prevention and treatment of pressure ulcers were originally developed in 1985 and revised in 1991 and 2002. The value of these guidelines can be questioned because it seems they are not in line with the beliefs and practice of the caregivers and only 5% of them are evidence-based. AIMS AND OBJECTIVES: To get a better insight into nurses' current knowledge, beliefs and performed practices relating to massage, a study was designed to assess changes in these three aspects after the publication of the 2002 Dutch national guidelines. The outcome was compared with the situation in 1991, the year in which the previous guidelines were published. DESIGN AND METHOD: A cross-sectional comparative study was designed using written questionnaires. Questions were formulated regarding knowledge and beliefs about prevention methods and the actual use of these methods in the prevention of pressure ulcers. The 2003-survey population consisted of nurses working in the Netherlands and was approached at random via subscriptions to Nursing News (i.e. Verpleegkunde Nieuws), a Dutch professional journal or via affiliations to an institution participating in the 2003 National Prevalence Survey of Pressure Ulcers. RESULTS AND CONCLUSIONS: Compared with the 1991 findings, the 2003 results show an improvement for the topic of pressure ulcers, but a deterioration regarding dehydration. It is obvious that the knowledge of the current CBO-guidelines on massage is still not widely distributed as it should be. Our overall conclusion is that the differences in responses between 1991 and 2003 are significant and suggest that the nurses were better informed in 2003. RELEVANCE TO CLINICAL PRACTICE: For the improvement of health care in the domain of pressure ulcer preventions, we need more than an accurate implementation of new or existing guidelines. Guidelines should also be based on qualitative, methodological well-designed studies to be evidence-based.

Adult↗
PubMed2005

Optimal time-points in clinical trials with linearly divergent treatment effects.

In repeated measures studies, equidistant time-points do not always yield efficient treatment effect estimators. In the present paper, the optimal allocation of time-points is calculated for a small number of repeated measures, different covariance structures and linearly divergent treatment effects. The gain in efficiency of the treatment effect estimator by using optimally allocated time-points instead of equidistant time-points or by adding optimally spaced measures (at the expense of patients) is then computed. The assumed covariance structure is crucial for the results. For a compound symmetric covariance structure, a large gain in efficiency is obtained by adding repeated measures at the end of the study. For a first-order auto-regressive covariance structure, highly efficient treatment effect estimators are obtained with only two repeated measures, i.e. at the start and at the end of the study. For a first-order auto-regressive covariance structure including measurement error, the gain in efficiency by adding optimally spaced measures depends on the covariance parameter values. The gain in efficiency is similar with or without a random intercept. For a fixed study budget, the commonly used design with more than two equally spaced measures was never optimal for the linear cost function and covariance structures that were used. If the covariance structure is unknown, the optimal design based on a first-order auto-regressive covariance structure with measurement error is preferable in terms of robustness against misspecification of the covariance structure. The numerical results are illustrated by two examples.

Clinical Trials as Topic↗
PubMed2005

Optimal number of repeated measures and group sizes in clinical trials with linearly divergent treatment effects.

The effect of number of repeated measures on the variance of the generalized least squares (GLS) treatment effect estimator is considered assuming a linearly divergent treatment effect, equidistant time-points and either a fixed number of subjects or a fixed study budget. The optimal combination of group sizes and number of repeated measures is calculated by minimizing this variance subject to a linear cost function. For a fixed number of subjects, the variance of the GLS treatment effect estimator can be decreased by adding intermediate measures per subject. This decrease is relatively large if a) the covariance structure is compound symmetric or b) the structure approaches compound symmetry and the correlation between two repeated measures does not exceed 0.80, or c) the correlation between two repeated measures does not exceed 0.60 if the time-lag goes to zero. In case the sample sizes and number of repeated measures are limited by budget constraints and the covariance structure includes a first-order auto-regression part, two repeated measures per subject yield highly efficient treatment effect estimators. Otherwise, it is more efficient to have more than two repeated measures. If the covariance structure is unknown, the optimal design based on a first-order auto-regressive structure with measurement error is preferable in terms of robustness against misspecification of the covariance structure. The numerical results are illustrated by three examples.

Costs and Cost Analysis↗
PubMed2005

The effects of massage as a method to prevent pressure ulcers. A review of the literature.

General information about the effects of massage to prevent pressure ulcers is limited. A literature search was conducted to provide more detailed knowledge about the effects of massage in general and in preventing the development of pressure ulcers in particular. Using the keywords massage, rubbing, prevention of pressure ulcers/pressure ulcers, and paying particular attention to referenced articles yielded a summary of different manual massage techniques and indications/contraindications of this intervention for both healthy tissues and tissues in patients at risk for developing pressure ulcers. A careful review of this information; the clinical, physical, and pathophysiological aspects of pressure ulcers, including extrinsic and intrinsic factor; and the time-pressure relationship suggests that one type of massage may be beneficial for persons who are at risk for developing pressure ulcers. Specifically, effleurage applied with moderate pressure is the most preferred massage in the treatment of pressure ulcers, although based on currently existing studies, it cannot be proven statistically that massage is an adequate preventive method for pressure ulcers. Although many guidelines advised against use of massage in people at risk for pressure ulcers, current evidence suggests that research to increase knowledge about the mechanism behind the effects of massage as part of an individualized prevention and treatment plan should be conducted.

Humans↗
PubMed2003

Citrulline: a physiologic marker enabling quantitation and monitoring of epithelial radiation-induced small bowel damage.

PURPOSE: Small bowel irradiation results in epithelial cell loss and consequently impairs function and metabolism. We investigated whether citrulline, a metabolic end product of small bowel enterocytes, can be used for quantifying radiation-induced epithelial cell loss. METHODS AND MATERIALS: NMRI mice were subjected to single-dose whole body irradiation (WBI). The time course of citrullinemia was assessed up to 11 days after WBI. A dose-response relationship was determined at 84 h after WBI. In addition, citrullinemia was correlated with morphologic parameters at this time point and used to calculate the dose-modifying factor (DMF) of glutamine and amifostine on acute small bowel radiation damage. RESULTS: After WBI, a time- and dose-dependent decrease in plasma citrulline level was observed with a significant dose-response relationship at 84 h. At this time point, citrullinemia significantly correlated with jejunal crypt regeneration (p < 0.001) and epithelial surface lining (p = 0.001). A DMF of 1.0 and 1.5 was computed at the effective dose 50 (ED50) level for glutamine and amifostine, respectively. CONCLUSIONS: Citrullinemia can be used to quantify acute small bowel epithelial radiation damage after single-dose WBI. Radiation-induced changes in citrullinemia are most pronounced at 3 1/2 to 4 days postirradiation. At this time point, citrullinemia correlates with morphologic endpoints for epithelial radiation damage.

Animals↗
PubMed2003

A comparison between traditional methods and multilevel regression for the analysis of multicenter intervention studies.

This article reviews three traditional methods for the analysis of multicenter trials with persons nested within clusters, i.e., centers, namely naïve regression (persons as units of analysis), fixed effects regression, and the use of summary measures (clusters as units of analysis), and compares these methods with multilevel regression. The comparison is made for continuous (quantitative) outcomes, and is based on the estimator of the treatment effect and its standard error, because these usually are of main interest in intervention studies. When the results of the experiment have to be valid for some larger population of centers, the centers in the intervention study have to present a random sample from this population and multilevel regression may be used. It is shown that the treatment effect and especially its standard error, are generally incorrectly estimated by the traditional methods, which should, therefore, not in general be used as an alternative to multilevel regression.

Adolescent↗
PubMed2003

Development of a model for case-mix adjustment of pressure ulcer prevalence rates.

BACKGROUND: Acute care hospitals participating in the Dutch national pressure ulcer prevalence survey use the results of this survey to compare their outcomes and assess their quality of care regarding pressure ulcer prevention. The development of a model for case-mix adjustment is essential for the use of these prevalence rates as an outcome measure. OBJECTIVE: The development of a valid model for case-mix adjustment to compare the prevalence rates in the acute care hospitals that participated in the 1998 Dutch pressure ulcer prevalence survey, for the purpose of performance comparisons among the hospitals. DESIGN: Cross-sectional design. SUBJECTS: Subjects were patients residing in the 43 acute care hospitals that participated in the national pressure ulcer prevalence survey on May 26, 1998. MEASURES: The study examined the validity of a model for case-mix adjustment of pressure ulcer prevalence rates and compared hospitals to evaluate the impact of adjusted prevalence rates on their performance. RESULTS: A logistic model was developed for case-mix adjustment, using age, malnutrition, incontinence, activity, mobility, sensory perception, friction and shear, and ward specialty. This model was found to have content, construct, and internal validity. Case-mix adjustment influenced the hospitals' performance. CONCLUSION: The data of the national pressure ulcer prevalence survey can be used to develop a valid model for case-mix adjustment. Conclusions about the quality of care were influenced by the use of case-mix adjusted outcomes as a measure of this quality.

Adolescent↗
PubMed2002

Maximin D-optimal designs for longitudinal mixed effects models.

In this article, the optimal selection and allocation of time points in repeated measures experiments is considered. D-optimal cohort designs are computed numerically for the first- and second-degree polynomial models with random intercept, random slope, and first-order autoregressive serial correlations. Because the optimal designs are locally optimal, it is proposed to use a maximin criterion. It is shown that, for a large class of symmetric designs, the smallest relative efficiency over the model parameter space is substantial.

Child↗