http://repub.eur.nl/res/aut/13768/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/34221/ 2011-05-01T00:00:00Z Background: Memory self-efficacy (MSE) is the belief about one's mastery of memory functioning. In healthy elderly, memory complaints are related to MSE rather than to objectively measured memory capacity. MSE has scarcely been studied in patients that suffered a stroke. The aim of this study was twofold: (1) to examine whether memory capacity and MSE can predict the presence of memory complaints in stroke patients, and (2) to study which variables are the best predictors of MSE. Methods: In a cross-sectional study, 136 stroke patients (>18 months after onset) were recruited from April 2008 to November 2009. MSE was measured using the Metamemory in Adulthood questionnaire. Depression, coping and personality were measured using validated questionnaires, and memory performance was measured using the Rivermead Behavioural Memory Test (RBMT) and the Auditory Verbal Learning Test (AVLT). Patients were divided into a 'complaints' and a 'no complaints' group. Results: A lower MSE score was an independent predictor of having memory complaints (adjusted odds ratio: 0.422; p = 0.000), adjusted for age and depression. The RBMT and AVLT scores did not predict the presence of memory complaints (p > 0.263). Presence of memory complaints and depression were the strongest predictors of MSE (B = -1.748, p = 0.000; B = -0.054, p = 0.000), followed by word fluency, not having a partner and side of stroke (B = 0.038, p = 0.012; B = -0.517, p = 0.082; B = -0.479, p = 0.088). Conclusions: Memory complaints are predicted by MSE rather than memory capacity. MSE memory training might be an effective training strategy for reducing memory complaints in selected chronic stroke patients. Copyright http://repub.eur.nl/res/pub/27828/ 2010-03-01T00:00:00Z Parameter uncertainty, patient heterogeneity, and stochastic uncertainty of outcomes are increasingly important concepts in medical decision models. The purpose of this study is to demonstrate the various methods to analyze uncertainty and patient heterogeneity in a decision model. The authors distinguish various purposes of medical decision modeling, serving various stakeholders. Differences and analogies between the analyses are pointed out, as well as practical issues. The analyses are demonstrated with an example comparing imaging tests for patients with chest pain. For complicated analyses step-by-step algorithms are provided. The focus is on Monte Carlo simulation and value of information analysis. Increasing model complexity is a major challenge for probabilistic sensitivity analysis and value of information analysis. The authors discuss nested analyses that are required in patient-level models, and in nonlinear models for analyses of partial value of information analysis. http://repub.eur.nl/res/pub/24416/ 2009-12-01T00:00:00Z Objective: To show how the bivariate random effects meta-analysis model can be used to study the relation between the explanatory variables and the performance of diagnostic tests as characterized by a summary receiver operating characteristic curve (SROCC). Study Design and Setting: The subject is discussed by means of a data example in which sensitivity and specificity are available for 149 studies on one of three tests for the diagnosis of coronary artery disease. The focus is on comparing SROCCs between different tests adjusted for potential confounders, but the methods can be applied much more generally. Results: Different types of SROCCs can be calculated. The influence of explanatory variables on an SROCC is an ensemble of sensitivity and specificity regression coefficients and covariance parameters. The regression coefficients of the SROCC are estimated and tested, and the percentage explained variability is determined. Under certain assumptions, the SROCCs of different covariate values do not cross. If these are fulfilled, it is much easier to describe the influence of explanatory variables. Conclusions can depend on the type of SROCC. Conclusion: The bivariate random effects meta-analysis model is an appropriate and convenient framework to investigate the effect of covariates on the performance of diagnostic tests as measured by SROCCs. http://repub.eur.nl/res/pub/14905/ 2008-09-01T00:00:00Z Meta-analysis of receiver operating characteristic (ROC)-curve data is often done with fixed-effects models, which suffer many shortcomings. Some random-effects models have been proposed to execute a meta-analysis of ROC-curve data, but these models are not often used in practice. Straightforward modeling techniques for multivariate random-effects meta-analysis of ROC-curve data are needed. The 1st aim of this article is to present a practical method that addresses the drawbacks of the fixedeffects summary ROC (SROC) method of Littenberg and Moses. Sensitivities and specificities are analyzed simultaneously using a bivariate random-effects model. The 2nd aim is to show that other SROC curves can also be derived from the bivariate model through different characterizations of the estimated bivariate normal distribution. Thereby the authors show that the bivariate random-effects approach not only extends the SROC approach but also provides a unifying framework for other approaches. The authors bring the statistical meta-analysis of ROC-curve data back into a framework of relatively standard multivariate meta-analysis with random effects. The analyses were carried out using the software package SAS (Proc NLMIXED). http://repub.eur.nl/res/pub/28920/ 2008-09-01T00:00:00Z Purpose: To determine the optimal width and timing of the electrocardiographic (ECG) pulsing window within the cardiac cycle in relation to heart rate (HR), image quality, and radiation exposure in patients who are suspected of having coronary artery disease. Materials and Methods: The institutional review board approved the study, and all patients gave informed consent. Dual-source computed tomography (CT) was performed in 301 patients (mean HR, 70.1 beats per minute ± 13.3 [standard deviation]; range, 43-112 beats per minute) by using a wide ECG pulsing window (25%-70% of the R-R interval). Data sets were reconstructed in 5% steps from 20%-75% of R-R interval. Image quality was assessed by two observers on a per-segment level and was classified as good or impaired. High-quality data sets were those in which each segment was of good quality. The width and timing of the image reconstruction window was calculated. On the basis of these findings, an optimal HR-dependent ECG pulsing protocol was designed, and the potential dose-saving effect on effective dose (in millisieverts) was calculated. Results: At low HR (≤65 beats per minute), high-quality data sets were obtained during end diastole (ED); at high HR (≥80 beats per minute), they were obtained during end systole (ES); and at intermediate HR (66-79 beats per minute), they were obtained during both ES and ED. Optimal ECG pulsing windows for low, intermediate, and high HR were at 60%-76%, 30%-77%, and 31%-47% of the R-R interval, respectively, and with these levels, the effective dose was decreased at low HR from 18.7 to 6.8 mSv, at intermediate HR from 14.7 to 13.4 mSv, and at high HR from 11.3 to 4.2 mSv. Conclusion: With optimal ECG pulsing, radiation exposure to patients, particularly those with low or high HR, can be reduced with preservation of image quality. http://repub.eur.nl/res/pub/28986/ 2008-02-12T00:00:00Z The aim of the study was to compare the diagnostic performance of endoscopic ultrasonography (EUS), computed tomography (CT), and18F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) in staging of oesophageal cancer. PubMed was searched to identify English-language articles published before January 2006 and reporting on diagnostic performance of EUS, CT, and/or FDG-PET in oesophageal cancer patients. Articles were included if absolute numbers of true-positive, false-negative, false-positive, and true-negative test results were available or derivable for regional, celiac, and abdominal lymph node metastases and/or distant metastases. Sensitivities and specificities were pooled using a random effects model. Summary receiver operating characteristic analysis was performed to study potential effects of study and patient characteristics. Random effects pooled sensitivities of EUS, CT, and FDG-PET for regional lymph node metastases were 0.80 (95% confidence interval 0.75-0.84), 0.50 (0.41-0.60), and 0.57 (0.43-0.70), respectively, and specificities were 0.70 (0.65-0.75), 0.83 (0.77-0.89), and 0.85 (0.76-0.95), respectively. Diagnostic performance did not differ significantly across these tests. For detection of celiac lymph node metastases by EUS, sensitivity and specificity were 0.85 (0.72-0.99) and 0.96 (0.92-1.00), respectively. For abdominal lymph node metastases by CT, these values were 0.42 (0.29-0.54) and 0.93 (0.86-1.00), respectively. For distant metastases, sensitivity and specificity were 0.71 (0.62-0.79) and 0.93 (0.89-0.97) for FDG-PET and 0.52 (0.33-0.71) and 0.91 (0.86-0.96) for CT, respectively. Diagnostic performance of FDG-PET for distant metastases was significantly higher than that of CT, which was not significantly affected by study and patient characteristics. The results suggest that EUS, CT, and FDG-PET each play a distinctive role in the detection of metastases in oesophageal cancer patients. For the detection of regional lymph node metastases, EUS is most sensitive, whereas CT and FDG-PET are more specific tests. For the evaluation of distant metastases, FDG-PET has probably a higher sensitivity than CT. Its combined use could however be of clinical value, with FDG-PET detecting possible metastases and CT confirming or excluding their presence and precisely determining the location(s). http://repub.eur.nl/res/pub/35115/ 2007-11-01T00:00:00Z Purpose: To obtain the best available estimates of the diagnostic performance of multidetector computed tomographic (CT) angiography compared with that of digital subtraction angiography (DSA) in the assessment of symptomatic lower extremity arterial disease and to identify the most important sources of variation in diagnostic performance between studies. Materials and Methods: Reports of studies published from January 2000 through April 2006 in English, German, French, or Spanish were searched for by using the MEDLINE, EMBASE, and Cochrane databases. Studies were included if they allowed construction of 2 X 2 contingency tables for the detection of stenosis of 50% or greater at multidetector CT angiography compared with that at DSA - the reference standard - in patients with claudication or critical ischemia. Two observers extracted data about study design, patient characteristics, arterial tracts, and technical protocols. Random-effects summary receiver operating characteristic analysis was performed to examine the influence of these data on diagnostic performance. Results: Of the 70 studies initially identified, 12 were included in which multidetector CT angiography was used to evaluate 9541 arterial segments in 436 patients. The pooled sensitivity and specificity for detecting a stenosis of at least 50% per segment were 92% (95% confidence interval: 89%, 95%) and 93% (9S% confidence interval: 91%, 95%), respectively. Three studies provided data about the diagnostic performance of multidetector CT angiography in subdivisions of the arterial tract. The diagnostic performance of multidetector CT angiography in the infrapopliteal tract was lower than but not significantly different from that in the aortoiliac (P > .11) and femoropopliteal (P > .40) tracts. Regression analysis showed that diagnostic performance was not significantly influenced by differences in study characteristics. Conclusion: Multidetector CT angiography is an accurate diagnostic test in the assessment of arterial disease (≥50% stenosis) of the entire lower extremity. http://repub.eur.nl/res/pub/11579/ 2007-09-01T00:00:00Z Objectives: The Medical Outcomes Study Short Form 36-Item Health Survey (SF-36) is the most widely used generic instrument to estimate quality of life of patients on renal replacement therapy. Purpose of this study was to summarize and compare the published literature on quality of life of hemodialysis (HD), peritoneal dialysis (PD), and renal transplant (RTx) patients. Methods: We used random-effects regression analyses to compare the SF-36 scores across treatment groups and adjusted this comparison for age and prevalence of diabetes using random-effects meta-regression analyses. Results: We found 52 articles that met the inclusion criteria, reporting quality of life of 36,582 patients. The unadjusted scores of all SF-36 health dimensions were not significantly different between HD and PD patients, but the scores of RTx patients were higher than those of dialysis patients, except for the dimensions Mental Health and Bodily Pain. Point differences between dialysis and RTx patients varied from 2 to 32. With adjustment for age and diabetes, the differences became smaller (point difference 2–22). The significance of the differences of both dialysis groups compared with RTx recipients disappeared for the dimensions Vitality and Social Functioning. The significance of the differences between HD and RTx patients disappeared on the dimensions Physical Functioning, Role Physical, and Bodily Pain. Conclusion: We conclude that dialysis patients have a lower quality of life than RTx patients, but this difference can partly be explained by differences in age and prevalence of diabetes. Keywords: hemodialysis, meta-analysis, peritoneal dialysis, quality of life, renal transplantation. http://repub.eur.nl/res/pub/35239/ 2007-09-01T00:00:00Z Background: Many studies have been published on the diagnostic performance of noninvasive tests for the assessment of coronary artery disease. The objective of the present study was to compare the published literature on the diagnostic performance of stress echocardiography, stress single-photon-emission computed tomography (SPECT), and electron beam computed tomography (EBCT). Methods: Meta-analytic studies on the diagnostic performance of imaging tests for coronary artery disease were searched in the Cochrane Library, PubMed, and bibliographies of selected articles. Sensitivities, specificities, and diagnostic odds ratios of the source studies were calculated per modality. Taking into account differences between studies, a random effects summary receiver operating characteristic analysis was performed. Results: We analyzed the data of 351 patient series, which were reported in 11 meta-analyses. The sensitivity of EBCT was significantly higher than that of stress SPECT, which had a significantly higher sensitivity than stress echocardiography (respectively, 93.1% [95% confidence interval, 90.7-95.6], 88.1 [95% confidence interval, 86.6-89.6], and 79.1% [95% confidence interval, 77.6-80.5]). The specificity of stress echocardiography was significantly higher than that of stress SPECT, which had a significantly higher specificity than EBCT (respectively, 87.1% [95% confidence interval, 85.7-88.5], 73.0% [95% confidence interval, 69.1-76.9], and 54.5% [95% confidence interval, 45.3-63.8]). The diagnostic odds ratios did not differ significantly between the 3 modalities, which resulted in one underlying summary receiver operating characteristic curve. Conclusions: This study suggests that there are no significant differences in the overall diagnostic performance between stress echocardiography, stress SPECT, and EBCT for the diagnosis of coronary artery disease. However, differences exist in sensitivity and specificity estimates, which may make each modality useful in different settings. http://repub.eur.nl/res/pub/35290/ 2007-08-01T00:00:00Z Purpose: To review the literature on the diagnostic performance of multidetector computed tomographic (CT) angiography for assessment of symptomatic coronary artery disease, with conventional coronary angiography as the reference standard. Materials and A PubMed and manual search of the literature published Methods: between January 1998 and May 2006 on use of multidetector CT angiography compared with coronary angiography in patients with symptomatic coronary artery disease was performed. Summary estimates of diagnostic odds ratio, sensitivity, and specificity were calculated. Random-effects models were used to compare the diagnostic performance of four-, 16-, and 64-detector CT angiographic units, and the proportion of nonassessable coronary arterial segments was evaluated. Results: Fifty-four studies were included in the meta-analysis: 22 studies with four-detector CT angiography, 26 with 16-detector CT angiography, and six with 64-detector CT angiography. The pooled sensitivity and specificity for detecting a greater than 50% stenosis per segment were 0.93 (95% confidence interval [CI]: 0.88, 0.97) and 0.96 (95% CI: 0.96, 0.97) for 64-detector CT angiography, 0.83 (95% CI: 0.76, 0.90) and 0.96 (95% CI: 0.95, 0.97) for 16-detector CT angiography, and 0.84 (95% CI: 0.81, 0.88) and 0.93 (95% CI: 0.91, 0.95) for four-detector CT angiography, respectively. Results of regression analysis indicated that the diagnostic performance significantly improved with the newer generations of multidetector CT scanners (64- and 16-detector vs four-detector units), adjusted for exclusion of nonassessable segments, and contrast agent concentration used (P < .05). Simultaneously, the nonassessable proportion of segments significantly decreased with the newer generations of multidetector CT scanners, adjusted for heart rate, prevalence of significant disease, and mean age. Conclusion: With the newer generations of multidetector CT scanners, the diagnostic performance for the assessment of coronary artery disease has significantly improved, and the proportion of nonassessable segments has decreased. http://repub.eur.nl/res/pub/13913/ 2005-10-01T00:00:00Z BACKGROUND AND PURPOSE: To evaluate duplex ultrasonographic thresholds for the determination of 70% to 99% stenosis of the ipsilateral and contralateral internal carotid artery in patients with symptoms of amaurosis fugax, transient ischemic attack (TIA), or minor stroke based on 2 criteria: maximizing accuracy and optimizing cost-effectiveness and to compare these with current recommendations. METHODS: From January 1997 to January 2000, a prospective multicenter study was conducted including 350 consecutive patients with symptoms of amaurosis fugax, TIA, or minor stroke who underwent bilateral duplex ultrasonography and digital subtraction angiography. A linear regression analysis was performed to estimate the degree of angiographic stenosis as a function of the peak systolic velocity (PSV). PSV thresholds were calculated for the ipsilateral and contralateral carotid arteries based on maximizing accuracy and optimizing cost-effectiveness. RESULTS: The PSV measurements significantly overestimated the angiographic stenosis in the contralateral artery (9.5%; 95% CI, 6.3% to 12.7%) compared with the ipsilateral carotid artery. The recommended PSV threshold for the diagnosis of 70% to 99% stenosis is 230 cm/s. Maximizing accuracy, the optimal PSV threshold for the ipsilateral artery was 280 cm/s, and for the contralateral artery, 370 cm/s for diagnosing a 70% to 99% stenosis. Optimizing cost-effectiveness, the optimal PSV threshold was 220 cm/s for ipsilateral and 290 cm/s for contralateral carotid arteries. CONCLUSIONS: PSV measurements overestimate the degree of angiographic stenosis in the contralateral carotid artery in patients with symptoms of amaurosis fugax, TIA, or minor stroke. Separate PSV thresholds should be used for the ipsilateral and contralateral carotid artery. PSV thresholds that optimize cost-effectiveness differ from the recommended thresholds and from thresholds that maximize accuracy. http://repub.eur.nl/res/pub/39807/ 2004-11-24T00:00:00Z Cardiovascular disease is the leading cause of death in industrialized countries. In the Netherlands approximately 50,000 patients die each year from cardiovascular disease, which is 35% of all deaths 1. In the United States, this number is over 930,000 patients per year 2. Cardiovascular disease includes all diseases of the heart or blood vessels. This thesis concentrates on arterial stenosis in the cardiovascular system, specifically in the coronary arteries, the carotid arteries, the peripheral arteries, and the renal arteries. Arterial stenosis in these areas may lead to severe morbidity due to, for example, myocardial infarction, stroke, limb amputation, or renal dysfunction, and thus has an enormous impact on the quality of life of the patient and may lead to death3-6. Therefore, it is important to diagnose cardiovascular disease accurately, so that adequate treatment can be initiated. http://repub.eur.nl/res/pub/8299/ 2003-01-01T00:00:00Z OBJECTIVE: To evaluate the discriminatory value and compare the predictive performance of six non-invasive tests used for perioperative cardiac risk stratification in patients undergoing major vascular surgery. DESIGN: Meta-analysis of published reports. METHODS: Eight studies on ambulatory electrocardiography, seven on exercise electrocardiography, eight on radionuclide ventriculography, 23 on myocardial perfusion scintigraphy, eight on dobutamine stress echocardiography, and four on dipyridamole stress echocardiography were selected, using a systematic review of published reports on preoperative non-invasive tests from the Medline database (January 1975 and April 2001). Random effects models were used to calculate weighted sensitivity and specificity from the published results. Summary receiver operating characteristic (SROC) curve analysis was used to evaluate and compare the prognostic accuracy of each test. The relative diagnostic odds ratio was used to study the differences in diagnostic performance of the tests. RESULTS: In all, 8119 patients participated in the studies selected. Dobutamine stress echocardiography had the highest weighted sensitivity of 85% (95% confidence interval (CI) 74% to 97%) and a reasonable specificity of 70% (95% CI 62% to 79%) for predicting perioperative cardiac death and non-fatal myocardial infarction. On SROC analysis, there was a trend for dobutamine stress echocardiography to perform better than the other tests, but this only reached significance against myocardial perfusion scintigraphy (relative diagnostic odds ratio 5.5, 95% CI 2.0 to 14.9). CONCLUSIONS: On meta-analysis of six non-invasive tests, dobutamine stress echocardiography showed a positive trend towards better diagnostic performance than the other tests, but this was only significant in the comparison with myocardial perfusion scintigraphy. However, dobutamine stress echocardiography may be the favoured test in situations where there is valvar or left ventricular dysfunction.