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.
Hypoglycemia is a frequent phenomenon in people being treated for diabetes mellitus, which can acutely disrupt driving performance. For the benefit of personal and public traffic safety, we decided ...to identify successful diabetes-related (SDR) behaviors to support safe driving for people with diabetes, from the perspective of experiential experts with diabetes mellitus. Experiential experts are people who can manage their own illness and conditions by developing expertise relevant to maintaining health and countering illness, and who are able to use this expertise to the benefit of peers.
The aim of our study was to objectify and systematize experiential expertise in terms of SDR behaviors, based on reports by experiential experts, to support safe driving for people with type 1 and type 2 diabetes mellitus. The emphasis was on preventing hypoglycemia as a short-term complication during driving.
We performed a mixed-methods study involving (i) semi-structured in-depth interviews with 33 experiential experts with diabetes mellitus from the Dutch Diabetes Association (DVN; Diabetesvereniging Nederland), in order to identify SDR behaviors regarding safe driving, and (ii) a validation study by means of a survey among a panel of 98 experiential experts (peers) from the DVN, to determine the extent to which they agreed with the communicability, importance, and feasibility of these behaviors for drivers with diabetes mellitus.
We identified a comprehensive set of 11 SDR behaviors, differentiated into seven general and four specific behaviors, to support safe driving. The general behaviors concern the following topics: (i) acquiring knowledge and information; (ii) acquiring and using self-measuring of blood glucose (SMBG) equipment; (iii) knowing one's physical response pattern; (iv) obtaining knowledge about the medication used; (v) preventing long-term eye complications; (vi) influencing factors that can affect blood glucose; and (vii) renewal procedure for driving license. The four specific behaviors refer to the following topics: (i) measures to be taken before driving; (ii) responding effectively to hypoglycemia while driving; (iii) informing and instructing passengers; and (iv) preventing hypoglycemia in drivers with type 2 diabetes mellitus not using SMBG equipment. Key factors for safe driving proved to be the ability of drivers to anticipate and respond effectively to hypoglycemia while driving and to inform and instruct fellow passengers. Participants of the validation survey agreed to a considerable degree with the communicability, importance, and feasibility of these behaviors to support safe driving for people with diabetes mellitus.
This study resulted in the identification and description of SDR behaviors to support safe driving. It proved possible to operationalize experiential expertise in terms of such behaviors. The next step is to have these behaviors validated by professional care providers in the field of diabetes, followed by translation into recommendations in self-management programs.
Multilevel analysis is a useful technique for analyzing longitudinal data. To describe a person's development across time, the quality of the estimates of the random coefficients, which relate time ...to individual changes in a relevant dependent variable, is of importance. The present study compares three estimators of the random coefficients: the Bayes estimator (BE), the empirical Bayes estimator (EBE), and the ordinary least squares estimator (OLSE). Using MLwiN, Monte Carlo simulations are carried out to study the performance of the estimators, while systematically varying the size of the sample as well as the number of measurement occasions. First, we examine for normally distributed random coefficients to what extent the EBE performs better than the OLSE and to what extent the EBE preserves the good properties of the BE. Second, we examine the robustness of the EBE which is based on a normal distribution of the random parameters, by comparing its performance to the OLSE for data being generated from two distributions other than the normal distribution: a modified t-distribution and a modified exponential distribution. As performance criteria we examine the Bayes risk as well as a criterion based on the frequentist notion of mean squared error.
Chest complaints presented to a general practitioner (GP) are frequently caused by diseases which have advantageous outcomes. However, in some cases, acute coronary syndrome (ACS) is present (1.5-22% ...of cases). The patient's signs, symptoms and electrocardiography results are insufficient diagnostic tools to distinguish mild disease from ACS. Therefore, most patients presenting chest complaints are referred to secondary care facilities where ACS is then ruled out in a majority of patients (78%). Recently, a point of care test for heart-type fatty acid-binding protein (H-FABP) using a low cut-off value between positive and negative of 4 ng/ml has become available. We aim to study the role of this point of care device in triage of patients presenting chest complaints possibly due to ACS, in primary care. Our research protocol is presented in this article. Results are expected in 2015.
Participating GPs will register signs and symptoms in all patients presenting chest complaints possibly due to ACS. Point of care H-FABP testing will also be performed. Our study will be a derivation study to identify signs and symptoms that, combined with point of care H-FABP testing, can be part of an algorithm to either confirm or rule out ACS. The diagnostic value for ACS of this algorithm in general practice will be determined.
A safe diagnostic elimination of ACS by application of the algorithm can be of significant clinical relevance. Improved triage and thus reduction of the number of patients with chest complaints without underlying ACS, that are referred to secondary care facilities, could lead to a substantial cost reduction.
ClinicalTrials.gov, NCT01826994, accepted April 8th 2013.
Abstract
Background: Catheter-related bloodstream infections (CRBSIs) can lead to increased morbidity and length of stay (LOS) in the intensive care unit (ICU). The purpose of this study was to ...analyse the incidence of catheter-related bloodstream infection associated with central venous catheters (CVCs) and arterial catheters (ACs) and to identify risk factors for CRBSIs in our ICU. Methods: This was a prospective observational study in a 17-bed medical-surgical ICU of a 715-bed university hospital. Patients admitted to the ICU for ≥ 24 h between 1 September 2007 and 30 April 2008, who received a CVC or AC, were included in the study. Results: A total of 219 patients with 258 CVCs and 336 ACs were included in the study and observed for a combined total of 3172 catheter-days. The CRBSI incidence density was 1.2 per 1000 catheter-days for CVCs and 2.1 per 1000 catheter-days for ACs. The mean LOS (p = 0.003), the number of days a catheter remained in situ (p = 0.001), and the length of pre-ICU in-hospital stay (p = 0.031) were significantly higher in the CRBSI group. Risk factor analysis was not reliable due to the low number of CRBSIs. Conclusion: The incidence of AC- and CVC-related CRBSIs was comparable to the incidence reported in the literature. However, the incidence for ACs was higher than for CVCs. In addition to CVCs, ACs should be considered a possible cause of catheter-related infections and both should be replaced when CRBSI is suspected.
Samenvatting
Inleiding:
Uit diverse studies is gebleken dat de toepassing van near-peer teaching in het trainen van medisch technische vaardigheden (skills) en in het tutoriaal probleemgestuurd ...onderwijs (PGO) gelijkwaardig is aan het door stafleden gegeven onderwijs. Het is echter nog onvoldoende onderzocht of ouderejaars studenten ook als docent van theoretisch, klinisch onderwijs kunnen functioneren. Daarom vergeleken wij in een gerandomiseerde crossover studie de kwaliteit en wenselijkheid van near-peer teaching met regulier onderwijs.
Methode:
Zesentwintig vierdejaars studenten geneeskunde kregen wekelijks een uur theoretisch onderwijs in de algemene interne geneeskunde. Dit onderwijs werd beurtelings gegeven door een zesdejaars student (semi-arts) en een staflid (internist-hematoloog). Coassistenten werden willekeurig ingedeeld in een groep die begon met de semi-arts en een groep die begon met de internist. Per student werden vier onderwijsmomenten geëvalueerd aan de hand van een vragenlijst bestaande uit 16 items; de gemiddelde scores van deze items (de totaalbeoordeling) werden vergeleken middels linear mixed models.
Resultaten:
In totaal werden 92 vragenlijsten verzameld. De totaalbeoordeling van het onderwijs was significant hoger bij de semi-arts (8.31); de internist scoorde 8.00 (p = 0.004). Uit de scores op de vragenlijst bleek dat er in het onderwijs door de semi-arts sprake was van meer interactiviteit en stimulatie in een plezierige leeromgeving, alsmede meer overzicht en fysiologische uitleg.
Conclusies:
Theoretisch onderwijs door een ouderejaars student wordt even hoog gewaardeerd als onderwijs door een staflid. Deze resultaten kunnen verklaard worden door de aanwezigheid van cognitieve en sociale congruentie, of door het feit dat didactische vaardigheden belangrijker zijn dan vakinhoudelijke kennis. (Wlazlo N, Winkens B, Vleuten CPM van der, Peters WG. Near-peer teaching in het coschap Interne Geneeskunde: een gerandomiseerde cross-over trial. Tijdschrift voor Medisch Onderwijs 2011;30(1-2):2-10)
Summary
Introduction:
The quality of near peer teaching has been shown to be similar to that of staff-led teaching during procedural skills training and PBL tutorials. It has not been investigated, however, if student-led formal teaching can be effective in clerkship settings. We conducted a randomised, cross over study to compare the quality and desirability of teacher led versus student led teaching during a clerkship in general internal medicine.
Methods:
Twenty-six fourth year medical students received weekly one-hour sessions of formal teaching. They were randomised to one of two groups. Both groups were taught alternately by a student and an internist, but one group started with a student-led session and the other group with a teacher-led session. All students evaluated four sessions by completing, for each session, a questionnaire consisting of sixteen items to be rated on a ten-point scale. The mean item scores (overall evaluation) were compared using linear mixed models.
Results:
A total of 92 completed questionnaires was obtained. The overall score was significantly higher for the student led (8.31) compared to the internist led (8.00; p = 0.004) sessions. This was due to higher scores on interaction, simulation, positive learning environment, overview and explanation of physiology.
Conclusions:
Evaluation scores on theoretical teaching during a general internal medicine clerkship were higher on sessions led by a student than on sessions led by a haematologist. These results may be explained by cognitive and social congruence or by teaching skills having a stronger impact than content expertise. (Wlazlo N, Winkens B, Vleuten CPM van der, Peters WG. Near-peer teaching during a general internal medicine clerkship: a randomised cross-over trial. Netherlands Journal of Medical Education 2011;30(1-2):2-10)
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