Publications by authors named "Olaf Dekkers"

Objective: The aim of this study was to perform a systematic review and meta-analysis on insulin resistance in adult patients with type 1 diabetes mellitus compared to healthy controls, assessed by hyperinsulinemic euglycemic clamp studies.

Design And Methods: We conducted a systematic search of publications using PubMed, EMBASE, Web of Science and COCHRANE Library. Hyperinsulinemic euglycemic clamp studies comparing adult patients with type 1 diabetes mellitus to healthy controls were eligible.

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Objective: We aimed to estimate pooled percentages of patients with adrenal insufficiency after treatment with corticosteroids for various conditions in a meta-analysis. Secondly, we aimed to stratify the results by route of administration, disease, treatment dose, and duration.

Methods: We searched seven electronic databases (PubMed, MEDLINE, EMBASE, COCHRANE, CENTRAL, Web of Science, and CINAHL/Academic Search Premier) in February 2014 to identify potentially relevant studies.

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Article Synopsis
  • Germline variants in the SDHD gene are linked to a higher risk of paragangliomas, and this study aimed to compare mortality rates of SDHD variant carriers in the Netherlands with the general population.
  • The research, conducted at Leiden University Medical Center, involved 275 SDHD variant carriers, predominantly with the c.274G>T, p.(Asp92Tyr) variant, who were monitored for mortality over an average follow-up of 7.6 years.
  • Findings showed that mortality rates among SDHD carriers were not significantly higher than those in the general population, with a standardized mortality ratio of 1.07, suggesting no substantial increase in mortality risk.
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The aim of this systematic review and meta-analysis was to investigate whether mortality is increased in patients biochemically cured after initial treatment for Cushing's disease. This is a systematic review and meta-analysis of follow-up studies in patients cured from Cushing's disease after initial treatment was performed. Eight electronic databases were searched from 1975 to March 2014 to identify potentially relevant articles.

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Problem: The aim of this meta-analysis was to evaluate whether specific maternal HLA alleles and HLA sharing of couples are associated with the occurrence of recurrent miscarriage (RM).

Method Of Study: A systematic literature search was performed for studies that evaluated the association between HLA alleles, HLA sharing and RM. RM was defined as three or more consecutive unexplained miscarriages and a control group was included of women with at least one live birth and no miscarriages in their history.

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Objectives: Forty percent of breast cancers occur among older patients. Unfortunately, there is a lack of evidence for treatment guidelines for older breast cancer patients. The aim of this study is to compare treatment strategy and relative survival for operable breast cancer in the elderly between The Netherlands and Ireland.

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Objective: Currently, little is known about the prevalence of thyroid tumors in multiple endocrine neoplasia type 1 (MEN1) patients and it is unclear whether tumorigenesis of these thyroid tumors is MEN1-related. The aim of the study was to assess the prevalence of thyroid incidentalomas in MEN1 patients compared with nonMEN1 patients and to verify whether thyroid tumorigenesis is MEN1-related.

Design: A cross-sectional study.

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Objectives: To compare noninferiority margins defined in study protocols and trial registry records with margins reported in subsequent publications.

Study Design And Setting: Comparison of protocols of noninferiority trials submitted 2001 to 2005 to ethics committees in Switzerland and The Netherlands with corresponding publications and registry records. We searched MEDLINE via PubMed, the Cochrane Controlled Trials Register (Cochrane Library issue 01/2012), and Google Scholar in September 2013 to identify published reports, and the International Clinical Trials Registry Platform of the World Health Organization in March 2013 to identify registry records.

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Recently, it has become apparent that superficial vein thrombosis (SVT) can have serious complications. However, the magnitude of the risk of subsequent deep venous and arterial thrombotic events remains unknown. We examined this in a nationwide population-based setting during a period when SVT was not treated routinely with anticoagulants.

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Thousands of patients and placebo-treated controls have been included in many clinical trials of stem cell therapy over the last decade or so, but often the study groups have been small. Their scientific value may therefore be limited and their ethical justification questionable. Would "crowd sourcing" for data sharing be a means of increasing the collective value of clinical trials? Here, we make a case for open access of all data emerging from stem cell studies (trials but also observational studies) independent of whether they are investigator-initiated or commercially driven.

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Objectives: Instrumental variable (IV) analysis is promising for estimation of therapeutic effects from observational data as it can circumvent unmeasured confounding. However, even if IV assumptions hold, IV analyses will not necessarily provide an estimate closer to the true effect than conventional analyses as this depends on the estimates' bias and variance. We investigated how estimates from standard regression (ordinary least squares [OLS]) and IV (two-stage least squares) regression compare on mean squared error (MSE).

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Context: Osteoporosis and fractures are prevalent after orthotopic liver transplantation (OLT), but data on these skeletal complications are scarce in patients with end-stage liver disease awaiting liver transplantation.

Objective: To evaluate the prevalence of vertebral fractures (VFs) in OLT recipients at the time of screening for transplantation and to establish the association between bone mineral density (BMD) and these fractures before transplantation.

Design And Setting: We conducted a retrospective study of consecutive OLT recipients at the Leiden University Medical Centre between 2000 and 2011 at the time of screening for transplantation.

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Background: It is suggested that the body posture during urination can influence urodynamic parameters in patients with Lower Urinary Tract Symptoms (LUTS) to an extent approaching pharmacological interventions. In this article, the influence of body position during micturition on maximum urinary flow rate (Qmax), voiding time (TQ) and post-void residual volume (PVR) in healthy males and patients with LUTS is analyzed by means of a systematic review and meta-analysis.

Evidence Acquisition: A systematic search was conducted in 14 medical databases.

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Background: Instrumental variable methods can potentially circumvent the unmeasured confounding inherent in observational data analyses.

Methods: We investigated the validity and usefulness of physician's preference instrumental variable analysis in the setting of a moderate-sized clinical study. Using routine care data from 476 elective cardiac surgery patients, we assessed the effect of preoperative corticosteroids on mechanical ventilation time and duration of intensive care and hospital stay, occurrence of infections, atrial fibrillation, heart failure, and delirium.

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Patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) are at risk for invasive aspergillosis (IA) even prior to the introduction of stem cell transplantation (SCT). In times of increasing triazole resistance and changing use of antifungal prophylaxis, insight into the risk factors for IA is needed to improve strategies for preventing IA in this population. Consecutive patients who received remission-induction therapy for AML or MDS at the Leiden Academic Medical Centre were included.

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Context: The natural course and survival of neuroendocrine tumors (NETs) of thymus (Th) and lung in multiple endocrine neoplasia type 1 (MEN1) patients are still unknown.

Objective: Our objective was to assess prevalence, tumor growth, and survival of Th and lung NETs in an unselected MEN1 population with long-term follow-up.

Design: This was an observational study.

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The evidence for application of silver-containing dressings and topicals in the treatment of partial-thickness burns in pediatric patients is largely based on clinical trials involving adult patients despite the important differences between the skin of children and adults. A systematic review and meta-analysis was performed of all randomized controlled trials comparing nonsilver treatment with silver-containing dressings and silver topical agents in children with partial-thickness burns in the acute stage. Endpoints were wound healing, grafting, infection, pain, number of dressing changes, length of hospital stay, and scarring.

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Iodothyronine deiodinases represent a family of selenoproteins involved in peripheral and local homeostasis of thyroid hormone action. Deiodinases are expressed in multiple organs and thyroid hormone affects numerous biological systems, thus genetic variation in deiodinases may affect multiple clinical endpoints. Interest in clinical effects of genetic variation in deiodinases has clearly increased.

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Hospital standardized mortality ratios (HSMR) are meant to compare mortality risks between hospitals. There is, however, much discussion about the value of the HSMR because incomplete adjustment for case mix is almost inevitable and because the data required to estimate HSMR are often unreliable. There is also a further problem with HSMR, which hampers its interpretation: the starting point for the HSMR is a comparison between the mortality outcomes of more than 50 common diagnoses, not between one or two well-defined treatments for one disease.

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Background: Annually, approximately 1-3% of patients treated with vitamin K antagonists (VKA) suffer from major haemorrhage. Since high levels of free thyroxine (fT4) are associated with increased thrombosis risk, the aim was to assess whether low levels of fT4 contribute to major haemorrhage in patients under VKA treatment.

Methods: The FACTORS (Factors in Oral Anticoagulant Safety) study is a case-control study on patients receiving VKA treatment, including 110 cases with major haemorrhage.

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Aims: Platelets play an important role in cardiovascular disease, and β-blockers are often prescribed for cardiovascular disease prevention. β-Blockers may directly affect platelet aggregation, because β-adrenergic receptors are present on platelets. There is uncertainty about the existence and magnitude of an effect of β-blockers on platelet aggregation.

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Osteoporosis is prevalent in end-stage liver disease, but data on long-term changes in bone mineral density (BMD) and related fracture incidence after orthotopic liver transplantation (OLT) are scarce. We evaluated BMD changes up to 5 years in consecutive recipients of a successful OLT at the Leiden University Medical Centre between 2000 and 2011, in whom sequential BMD data were available. Spinal radiographs were available at time of screening and at 6 and 12 months post-OLT and were assessed for vertebral fractures by two independent observers using Genant's semiquantitative method.

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Objective: Patients treated for nonfunctioning pituitary macroadenoma (NFMA) with suprasellar extension show disturbed sleep characteristics, possibly related to hypothalamic dysfunction. In addition to hypopituitarism, both structural hypothalamic damage and sleep restriction per se are associated with the metabolic syndrome. However, the prevalence of the metabolic syndrome in patients with NFMA is not well established.

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Background: While some prediction models have been developed for diabetic populations, prediction rules for mortality in diabetic dialysis patients are still lacking. Therefore, the objective of this study was to identify predictors for 1-year mortality in diabetic dialysis patients and use these results to develop a prediction model.

Methods: Data were used from the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD), a multicenter, prospective cohort study in which incident patients with end stage renal disease (ESRD) were monitored until transplantation or death.

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