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Biomedical subjects

Ingeborg van der Tweel

Publications and source records attributed to Ingeborg van der Tweel.

At least 19 recordsLinked to original sources
PubMed2006

Heart disease risk determines menopausal age rather than the reverse.

OBJECTIVES: The purpose of this study was to investigate whether a harmful cardiovascular risk profile accelerates menopause. BACKGROUND: Women with an early menopause are at an increased risk of cardiovascular disease. Although increased cardiovascular risk has been proposed as consequence of menopause, the alternative hypothesis, that increased premenopausal cardiovascular risk promotes early menopause, needs to be examined. METHODS: We used data from the Framingham Heart Study cohort. This study started in 1948 and has followed up participants biennially since then. Women who were premenopausal at study entry and who reached natural menopause after at least two examination rounds were included in the study (n = 695). Premenopausal age-independent levels of serum total cholesterol, relative weight, blood pressure, and Framingham risk score were determined, as well as premenopausal changes in cholesterol, body weight, and blood pressure. RESULTS: A higher premenopausal serum total cholesterol level was statistically significantly associated with an earlier age at menopause, as were increases in total serum cholesterol, relative weight, and blood pressure in the premenopausal period. A decrease in total serum cholesterol during premenopause was statistically significantly associated with later age at menopause. Decreasing blood pressure was associated with a later menopausal age, but this association was not statistically significant. A decrease in relative weight was associated with a significant earlier age at menopause. Each 1% higher premenopausal Framingham risk score was associated with a decrease in menopausal age of 1.8 years (95% confidence interval -2.72 to -0.92). CONCLUSIONS: The findings support the view that heart disease risk determines age at menopause. This offers a novel explanation for the inconsistent findings on cardiovascular disease rate and its relationship to menopausal age and effects of hormone replacement therapy.

Adult↗
PubMed2006

Minimally invasive 'step-up approach' versus maximal necrosectomy in patients with acute necrotising pancreatitis (PANTER trial): design and rationale of a randomised controlled multicenter trial [ISRCTN13975868].

BACKGROUND: The initial treatment of acute necrotizing pancreatitis is conservative. Intervention is indicated in patients with (suspected) infected necrotizing pancreatitis. In the Netherlands, the standard intervention is necrosectomy by laparotomy followed by continuous postoperative lavage (CPL). In recent years several minimally invasive strategies have been introduced. So far, these strategies have never been compared in a randomised controlled trial. The PANTER study (PAncreatitis, Necrosectomy versus sTEp up appRoach) was conceived to yield the evidence needed for a considered policy decision. METHODS/DESIGN: 88 patients with (suspected) infected necrotizing pancreatitis will be randomly allocated to either group A) minimally invasive 'step-up approach' starting with drainage followed, if necessary, by videoscopic assisted retroperitoneal debridement (VARD) or group B) maximal necrosectomy by laparotomy. Both procedures are followed by CPL. Patients will be recruited from 20 hospitals, including all Dutch university medical centres, over a 3-year period. The primary endpoint is the proportion of patients suffering from postoperative major morbidity and mortality. Secondary endpoints are complications, new onset sepsis, length of hospital and intensive care stay, quality of life and total (direct and indirect) costs. To demonstrate that the 'step-up approach' can reduce the major morbidity and mortality rate from 45 to 16%, with 80% power at 5% alpha, a total sample size of 88 patients was calculated. DISCUSSION: The PANTER-study is a randomised controlled trial that will provide evidence on the merits of a minimally invasive 'step-up approach' in patients with (suspected) infected necrotizing pancreatitis.

Drainage↗
PubMed2006

Oral decontamination with chlorhexidine reduces the incidence of ventilator-associated pneumonia.

RATIONALE: Ventilator-associated pneumonia (VAP) is the most frequently occurring nosocomial infection associated with increased morbidity and mortality. Although oral decontamination with antibiotics reduces incidences of VAP, it is not recommended because of potential selection of antibiotic-resistant pathogens. We hypothesized that oral decontamination with either chlorhexidine (CHX, 2%) or CHX/colistin (CHX/COL, 2%/2%) would reduce and postpone development of VAP, and oral and endotracheal colonization. OBJECTIVES: To determine the effect of oral decontamination with CHX or CHX/COL on VAP incidence and time to development of VAP. METHODS: Consecutive patients needing mechanical ventilation for 48 h or more were enrolled in a randomized, double-blind, placebo-controlled trial with three arms: CHX, CHX/COL, and placebo (PLAC). Trial medication was applied every 6 h into the buccal cavity. Oropharyngeal swabs were obtained daily and quantitatively analyzed for gram-positive and gram-negative microorganisms. Endotracheal colonization was monitored twice weekly. RESULTS: Of 385 patients included, 130 received PLAC, 127 CHX and 128 CHX/COL. Baseline characteristics were comparable. The daily risk of VAP was reduced in both treatment groups compared with PLAC: 65% (hazard ratio [HR]=0.352; 95% confidence interval [CI], 0.160, 0. 791; p=0.012) for CHX and 55% (HR=0.454; 95% CI, 0.224, 0. 925; p=0.030) for CHX/COL. CHX/COL provided significant reduction in oropharyngeal colonization with both gram-negative and gram-positive microorganisms, whereas CHX mostly affected gram-positive microorganisms. Endotracheal colonization was reduced for CHX/COL patients and to a lesser extent for CHX patients. No differences in duration of mechanical ventilation, intensive care unit stay, or intensive care unit survival could be demonstrated. CONCLUSIONS: Topical oral decontamination with CHX or CHX/COL reduces the incidence of VAP.

Administration, Topical↗
PubMed2006

Feasibility and effects of the semirecumbent position to prevent ventilator-associated pneumonia: a randomized study.

CONTEXT: Reducing aspiration of gastric contents by placing mechanically ventilated patients in a semirecumbent position has been associated with lower incidences of ventilator-associated pneumonia (VAP). The feasibility and efficacy of this intervention in a larger patient population, however, are unknown. OBJECTIVE: Assessment of the feasibility of the semirecumbent position for intensive care unit patients and its influence on development of VAP. DESIGN: In a prospective multicentered trial, critically ill patients undergoing mechanical ventilation were randomly assigned to the semirecumbent position, with a target backrest elevation of 45 degrees , or standard care (i.e., supine position) with a backrest elevation of 10 degrees . MAIN OUTCOME MEASURES: Backrest elevation was measured continuously during the first week of ventilation with a monitor-linked device. A deviation of position was defined as a change of the randomized position >5 degrees . Diagnosis of VAP was made by quantitative cultures of samples obtained by bronchoscopic techniques. RESULTS: One hundred nine patients were assigned to the supine group and 112 to the semirecumbent group. Baseline characteristics were comparable for both groups. Average elevations were 9.8 degrees and 16.1 degrees at day 1 and day 7, respectively, for the supine group and 28.1 degrees and 22.6 degrees at day 1 and day 7, respectively, for the semirecumbent group (p < .001). The target semirecumbent position of 45 degrees was not achieved for 85% of the study time, and these patients more frequently changed position than supine-positioned patients. VAP was diagnosed in eight patients (6.5%) in the supine group and in 13 (10.7%) in the semirecumbent group (NS), after a mean of 6 (range, 3-9) and 7 (range, 3-12) days, respectively. There were no differences in numbers of patients undergoing enteral feeding, receiving stress ulcer prophylaxis, or developing pressure sores or in mortality rates or duration of ventilation and intensive care unit stay between the groups. CONCLUSIONS: The targeted backrest elevation of 45 degrees for semirecumbent positioning was not reached in the conditions of the present randomized study. The achieved difference in treatment position (28 degrees vs. 10 degrees ) did not prevent the development of VAP.

APACHE↗
PubMed2005

Effect of increased convective clearance by on-line hemodiafiltration on all cause and cardiovascular mortality in chronic hemodialysis patients - the Dutch CONvective TRAnsport STudy (CONTRAST): rationale and design of a randomised controlled trial [ISRCTN38365125].

BACKGROUND: The high incidence of cardiovascular disease in patients with end stage renal disease (ESRD) is related to the accumulation of uremic toxins in the middle and large-middle molecular weight range. As online hemodiafiltration (HDF) removes these molecules more effectively than standard hemodialysis (HD), it has been suggested that online HDF improves survival and cardiovascular outcome. Thus far, no conclusive data of HDF on target organ damage and cardiovascular morbidity and mortality are available. Therefore, the CONvective TRAnsport STudy (CONTRAST) has been initiated. METHODS: CONTRAST is a Dutch multi-center randomised controlled trial. In this trial, approximately 800 chronic hemodialysis patients will be randomised between online HDF and low-flux HD, and followed for three years. The primary endpoint is all cause mortality. The main secondary outcome variables are fatal and non-fatal cardiovascular events. CONCLUSION: The study is designed to provide conclusive evidence whether online HDF leads to a lower mortality and less cardiovascular events as compared to standard HD.

Journal Article↗
PubMed2005

Results and complications after ileal pouch anal anastomosis: a meta-analysis of 43 observational studies comprising 9,317 patients.

OBJECTIVE: To analyze the literature of ileal pouch anal anastomosis (IPAA) regarding complications and functional outcome, to provide audit data for individual surgeons and units to assess their own performance against and also to serve as reference standard for the assessment of novel alternatives. BACKGROUND: IPAA is the standard restorative procedure for ulcerative colitis (UC) and familial adenomatous polyposis (FAP). This operation is, however, associated with distinct rates of failure, complications and fecal incontinence. METHODS: A meta-analysis on pooled incidences of complications of IPAA was conducted. Medline search and cross-reference search identified studies on IPAA (n > or = 50). Two authors independently performed the data extraction on study characteristics, diagnosis, type of operation, pouch-related complications, pouch failure and functional results. In case of disagreement consensus was reached by joint review of the study. Estimates of pouch-related complications, pouch failure and functional results are described as pooled percentages with 95% confidence interval. RESULTS: The initial search based on 1,206 abstracts yielded 43 studies eligible for further analysis. Indications for IPAA were UC in 87.5%, FAP in 8.9% and other diagnoses in 3.6%. The median follow-up was 36.7 months. Pouch failure was 6.8%, increasing to 8.5% in case of follow-up of more than 60 months. Pelvic sepsis occurred in 9.5%. Severe, mild and urge fecal incontinence were reported in 3.7, 17, and 7.3%, respectively. No effect of experience, duration of follow-up and type of surgical technique on the incidence of pouch failure and pelvic sepsis was demonstrable. CONCLUSIONS: Current techniques for restorative surgery after proctocolectomy are associated with non-negligible complication rates and leave room for improvement and continuation of development of alternative procedures.

Colitis, Ulcerative↗
PubMed2005

Repeated looks at accumulating data: to correct or not to correct?

Sequential analysis is a statistical way of analysing cumulative data. Its goal is to come to a decision as soon as enough evidence is reached for one or another hypothesis. In this article three different statistical approaches, the frequentist, the Bayesian and the likelihood approach, are discussed in relation to sequential analysis. In particular, the less known likelihood approach is elucidated.

Bayes Theorem↗
PubMed2005

Postmigration living problems and common psychiatric disorders in Iraqi asylum seekers in the Netherlands.

In a previous community-based, national study among Iraqi asylum seekers, a long asylum procedure was found to have a higher risk for common psychiatric disorders than adverse life events in Iraq. In the present article, the postmigration period is considered in more detail and evaluated in relationship with psychiatric disorders. Respondents were interviewed with fully structured, culturally validated, translated questionnaires. With the use of a Post- migration Living Problems questionnaire, worries about all kinds of problems were gathered. Psychiatric (DSM-IV) disorders were measured with the Composite International Diagnostic Interview 2.1. Factor analysis was done on the postmigration living problems, and in univariate and multivariate analyses, associations with psychopathology were calculated. Results show that clusters of postmigration living problems could be identified: family issues, discrimination, asylum procedure, socioeconomic living conditions, socioreligious aspects, and work-related issues. There was a significant relationship between all clustered postmigration living problems and psychopathology, except for socioreligious aspects. Multivariate logistic regression showed that lack of work, family issues, and asylum procedure stress had the highest odds ratios for psychopathology. The findings appeal to governments to shorten the asylum procedures, allow asylum seekers to work, and give preference to family reunion. Mental health workers should recognize the impact of postmigration living problems and consider focusing their treatment on coping with these problems instead of traumas from the past.

Adaptation, Psychological↗
PubMed2004

Sequential tests for gene-environment interactions in matched case-control studies.

The sample size necessary to detect a significant gene x environment interaction in an observational study can be large. For reasons of cost-effectiveness and efficient use of available biological samples we investigated the properties of sequential designs in matched case-control studies to test for both non-hierarchical and hierarchical interactions. We derived the test statistics Z and V and their characteristics when applied in a two-sided triangular test. Results of simulations show good agreement with theoretical values for V and the type I error. Power values were larger than their theoretical values for very large sample sizes. Median gain in efficiency was about 27 per cent. For a 'rare' phenotype gain in efficiency was larger when the alternative hypothesis was true than under the null hypothesis. Sequential designs lead to substantial efficiency gains in tests for interaction in matched case-control studies.

Breast Neoplasms↗
PubMed2004

Cannabis use and age at onset of schizophrenia.

OBJECTIVE: The purpose of the study was to assess the independent influences of gender and cannabis use on milestones of early course in schizophrenia. METHOD: In this population-based, first-contact incidence study conducted in The Hague, the Netherlands, patients (N=133) were interviewed with the Comprehensive Assessment of Symptoms and History, and key informants were interviewed with the Instrument for the Retrospective Assessment of the Onset of Schizophrenia. Milestones of early course were 1) first social and/or occupational dysfunction, 2) first psychotic episode, and 3) first negative symptoms. RESULTS: Male patients were significantly younger than female patients at first social and/or occupational dysfunction, first psychotic episode, and first negative symptoms. Cannabis-using patients were significantly younger at these milestones than were patients who did not use cannabis. Multivariate analyses showed that cannabis use, but not gender, made an independent contribution to the prediction of age at first psychotic episode: male cannabis users were a mean of 6.9 years younger at illness onset than male nonusers. In contrast, age at first social and/or occupational dysfunction and the risk of developing negative symptoms before the first contact with a physician for treatment of possible psychotic disorder were predicted by gender, but not by cannabis use. CONCLUSIONS: The results indicate a strong association between use of cannabis and earlier age at first psychotic episode in male schizophrenia patients. Additional studies examining this possibly causal relationship are needed.

Adolescent↗
PubMed2004

Diagnostic stability in a Dutch psychosis incidence cohort.

BACKGROUND: No study outside the UK has examined the diagnostic stability of psychotic disorders in a population-based sample. AIMS: To determine diagnostic stability in a Dutch population-based psychosis incidence cohort, to examine the frequencies of diagnostic shifts to and from schizophrenic disorders and to report the revised relative risks of schizophrenic disorders for immigrants. METHOD: A 30-month follow-up study assessed the cohort (n=181) by means of face-to-face diagnostic interviews. RESULTS: Diagnostic stability of schizophrenic disorders was high (91%), but lower for other psychotic disorders. At follow-up, the initial diagnosis was adjusted to schizophrenic disorder more often than that the reverse occurred. Almost half (49%) of the patients who were not initially diagnosed as having a schizophrenic disorder received this diagnosis at follow-up. The relative risks for most immigrant groups were stable. CONCLUSIONS: Schizophrenic disorders are underdiagnosed, rather than overdiagnosed, at first presentation.

Cohort Studies↗
PubMed2004

Sequential designs for clinical trials in amyotrophic lateral sclerosis.

BACKGROUND: The objective of this paper is to discuss the sequential trial design and its advantages in clinical trials for ALS. The sequential trial design is an alternative to the classical trial design, which permits stopping a study as soon as a treatment effect can be significantly demonstrated or denied. METHODS: As an example of a sequential survival analysis, a recently completed clinical trial is described. A secondary outcome measure used in the same trial, the decline of the vital lung capacity, was re-analyzed sequentially, in order to illustrate the use of the sequential method for a non-survival variable. To compare the classical with the sequential trial design, the number of patients needed in trials aiming at survival effects ranging from 10% to 20% with a power of 80% or 90% was calculated for both designs. RESULTS: In the given examples the time needed to prove the null hypothesis in the survival analysis, and the number of patients needed to prove the null hypothesis in the analysis of the vital capacity is lower than would have been the case in a classical analysis. In 18 of 24 different situations, the chance is at least 90% that with a sequential trial design fewer patients are needed. CONCLUSIONS: We argue that, particularly for ALS trials, a sequential design may be superior to a classical trial design, as it most often requires fewer patients than classically designed trials of equal power, and more importantly may avoid unnecessary continuation.

Amyotrophic Lateral Sclerosis↗
PubMed2003

Cognitive impairment is related to cerebral lactate in patients with carotid artery occlusion and ipsilateral transient ischemic attacks.

BACKGROUND AND PURPOSE: Patients with carotid artery occlusion (CAO) and ipsilateral transient ischemic attack (TIA) can have lasting cognitive impairment, despite the recovery of focal neurological deficits. We sought to assess whether cognitive impairment in these patients is associated with hemodynamic compromise and/or impaired cerebral metabolism. METHODS: In 39 consecutive patients with a TIA associated with an angiographically proven occlusion of the carotid artery, we examined (1) cognitive functioning, (2) cerebrovascular reserve capacity of the middle cerebral artery ipsilateral to the CAO as measured by transcranial Doppler ultrasound, and (3) metabolic ratios as measured by 1H-MR spectroscopy in the centrum semiovale ipsilateral to the symptomatic CAO. Findings were compared with those in healthy control subjects. RESULTS: As a group, patients were cognitively impaired. Mean CO2 reactivity and the mean ratio of N-acetyl aspartate to creatine were decreased. In approximately one third of patients, lactate was present in noninfarcted regions. The presence of lactate proved to be a stronger correlate of cognitive impairment than MRI-detected lesions (beta=0.41 versus beta=0.15). Cognitive impairment did not correlate with CO2 reactivity or the ratio of N-acetyl aspartate to creatine. CONCLUSIONS: This exploratory study in patients with CAO and ipsilateral TIA showed that 1H-MR spectroscopy-detected lactate in noninfarcted regions is a better indicator of cognitive impairment than MRI-detected lesions. Cognitive impairment did not correlate with CO2 reactivity.

Adult↗
PubMed2003

A randomized sequential trial of creatine in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a fatal disease with no cure. In a transgenic mouse model of ALS, creatine monohydrate showed a promising increase in survival. We performed a double-blind, placebo-controlled, sequential clinical trial to assess the effect of creatine monohydrate on survival and disease progression in patients with ALS. Between June 2000 and December 2001, 175 patients with probable, probable-laboratory supported, or definite ALS were randomly assigned to receive either creatine monohydrate or placebo 10 gm daily. A sequential trial design was used with death, persistent assisted ventilation, or tracheostomy as primary end points. Secondary outcome measurements were rate of decline of isometric arm muscle strength, forced vital capacity, functional status, and quality of life. The trial was stopped when the null hypothesis of indifference was accepted. Creatine did not affect survival (cumulative survival probability of 0.70 in the creatine group vs 0.68 in the placebo group at 12 months, and 0.52 in the creatine group vs 0.47 in the placebo group at 16 months), or the rate of decline of functional measurements. Creatine intake did not cause important adverse reactions. This placebo-controlled trial did not find evidence of a beneficial effect of creatine monohydrate on survival or disease progression in patients with ALS.

Aged↗
PubMed2003

Cognitive impairment in patients with carotid artery occlusion and ipsilateral transient ischemic attacks.

Although transient ischemic attacks (TIAs) by definition do not cause lasting neurological deficits, cognitive impairment has been suggested in patients with carotid artery disease who have suffered from a TIA. The purpose of our study was to assess whether patients with carotid artery disease and TIAs are cognitively impaired, to describe the frequency, nature and severity of this impairment, and to search for associated patient characteristics.Thirty-nine consecutive patients with carotid occlusion and ipsilateral cerebral or retinal TIAs, and 46 healthy controls underwent extensive neuropsychological assessment. Performances were compared group-wise with analysis of variance. In addition, the presence of cognitive impairment in the individual patient was determined. Associations between illness characteristics and cognitive impairment were explored with regression analysis.Fifty-four percent of patients were cognitively impaired. Cognitive deficits were non-specific in nature and mild in severity. Impairment occurred also in patients with isolated retinal symptoms and in those without visible ischemic brain lesions on MRI. Neither the presence of any vascular risk factor, the side of the symptomatic carotid occlusion, the uni- or bilaterality of carotid occlusion, nor the number of cerebral ischemic lesions were predictors of cognitive impairment. We conclude that about half of the patients with carotid artery occlusion and ipsilateral TIAs are cognitively impaired. The presence of cognitive deficits in patients with isolated retinal symptoms and in those without cerebral ischemic lesions on MRI argues against an exclusive role for structural brain damage in the pathogenesis of these deficits.

Adult↗
PubMed2003

Early stopping in clinical trials and epidemiologic studies for "futility": conditional power versus sequential analysis.

Early stopping of a clinical trial is well accepted when there is enough evidence for a significant effect. However, during the course of a trial, there can be reasons to consider early termination for "futility." In epidemiologic studies, costly or destructive laboratory tests or slow case accrual can make it desirable to stop a study early for reasons of efficiency. Estimation of the conditional power (CP) is proposed as a decision tool to stop a study early or to continue it. We consider the disadvantages of this method. We propose (group) sequential continuation of the trial or study as a less arbitrary strategy. We re-analyzed two data sets from the literature to illustrate the advantages of a sequential approach. We conclude that (group) sequential analyses have several advantages over CP. More studies should consider a sequential design and analysis to enable early stopping when enough evidence has accumulated to conclude a lack of the expected effect. Such a strategy can save valuable resources for more promising hypotheses.

Antibodies, Viral↗
PubMed2002

Cataract after total body irradiation and bone marrow transplantation: degree of visual impairment.

PURPOSE: To assess the degree of visual impairment as a result of cataract formation after total body irradiation (TBI) for bone marrow transplantation. METHODS AND MATERIALS: The data from 93 patients who received TBI in 1 or 2 fractions as a part of their conditioning regimen for bone marrow transplantation were analyzed with respect to the degree of visual impairment as a result of cataract formation. The probability to develop severe visual impairment (SVI) was determined for all patients, and the degree of visual impairment was assessed for 56 patients with stabilized cataract, using three categories: no, mild, or severe. RESULTS: For all 93 patients, the probability of developing a cataract causing SVI was 0.44. For allogeneic patients, it was 0.33 without and 0.71 with steroid treatment (p <0.001). All SVI-free probability curves reached a plateau distinct from the cataract-free curves. Apparently, cataracts developing late in the follow-up period rarely cause SVI. Of the patients with stabilized cataract, 32% had no visual impairment, 16% had mild, and 52% severe impairment. No or mild visual impairment was present in 61% of all patients with stable cataract and no steroid treatment compared with only 13% of the patients treated with steroids (p = 0.035). CONCLUSION: SVI occurs in only some of the patients (52%) with stable cataract after TBI for bone marrow transplantation in 1 or 2 fractions. Steroid treatment markedly increases the probability of developing visual problems as result of a cataract after TBI.

Acute Disease↗