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Featured researches published by N. Smidt.


The Australian journal of physiotherapy | 2005

Effectiveness of exercise therapy: A best-evidence summary of systematic reviews

N. Smidt; H.C.W. de Vet; L.M. Bouter; J. Dekker; J.H. Arendzen; R.A. de Bie; S.M. Bierma-Zeinstra; Paul J. M. Helders; S.H.J. Keus; G. Kwakkel; Ton Lenssen; R.A.B. Oostendorp; Raymond Ostelo; M. Reijman; Caroline B. Terwee; C. Theunissen; Siep Thomas; M. E. van Baar; A. van 't Hul; R.P. van Peppen; Arianne P. Verhagen; D.A.W.M. van der Windt

The purpose of this project was to summarise the available evidence on the effectiveness of exercise therapy for patients with disorders of the musculoskeletal, nervous, respiratory, and cardiovascular systems. Systematic reviews were identified by means of a comprehensive search strategy in 11 bibliographic databases (08/2002), in combination with reference tracking. Reviews that included (i) at least one randomised controlled trial investigating the effectiveness of exercise therapy, (ii) clinically relevant outcome measures, and (iii) full text written in English, German or Dutch, were selected by two reviewers. Thirteen independent and blinded reviewers participated in the selection, quality assessment and data-extraction of the systematic reviews. Conclusions about the effectiveness of exercise therapy were based on the results presented in reasonable or good quality systematic reviews (quality score > or = 60 out of 100 points). A total of 104 systematic reviews were selected, 45 of which were of reasonable or good quality. Exercise therapy is effective for patients with knee osteoarthritis, sub-acute (6 to 12 weeks) and chronic (> or = 12 weeks) low back pain, cystic fibrosis, chronic obstructive pulmonary disease, and intermittent claudication. Furthermore, there are indications that exercise therapy is effective for patients with ankylosing spondylitis, hip osteoarthritis, Parkinsons disease, and for patients who have suffered a stroke. There is insufficient evidence to support or refute the effectiveness of exercise therapy for patients with neck pain, shoulder pain, repetitive strain injury, rheumatoid arthritis, asthma, and bronchiectasis. Exercise therapy is not effective for patients with acute low back pain. It is concluded that exercise therapy is effective for a wide range of chronic disorders.


Neurology | 2006

The quality of diagnostic accuracy studies since the STARD statement Has it improved

N. Smidt; Anne Wilhelmina Saskia Rutjes; D.A.W.M. van der Windt; Raymond Ostelo; Patrick M. Bossuyt; Johannes B. Reitsma; L.M. Bouter; H.C.W. de Vet

Objective: To assess whether the quality of reporting of diagnostic accuracy studies has improved since the publication of the Standards for the Reporting of Diagnostic Accuracy studies (STARD statement). Methods: The quality of reporting of diagnostic accuracy studies published in 12 medical journals in 2000 (pre-STARD) and 2004 (post-STARD) was evaluated by two reviewers independently. For each article, the number of reported STARD items was counted (range 0 to 25). Differences in completeness of reporting between articles published in 2000 and 2004 were analyzed, using multilevel analyses. Results: We included 124 articles published in 2000 and 141 articles published in 2004. Mean number of reported STARD items was 11.9 (range 3.5 to 19.5) in 2000 and 13.6 (range 4.0 to 21.0) in 2004, an increase of 1.81 items (95% CI: 0.61 to 3.01). Articles published in 2004 reported the following significantly more often: methods for calculating test reproducibility of the index test (16% vs 35%); distribution of the severity of disease and other diagnoses (23% vs 53%); estimates of variability of diagnostic accuracy between subgroups (39% vs 60%); and a flow diagram (2% vs 12%). Conclusions: The quality of reporting of diagnostic accuracy studies has improved slightly over time, without a more pronounced effect in journals that adopted the STARD statement. As there is still room for improvement, editors should mention the use of the STARD statement as a requirement in their guidelines for authors, and instruct reviewers to check the STARD items. Authors should include a flow diagram in their manuscript.


Annals of Medicine | 2003

Effectiveness of physiotherapy for lateral epicondylitis: a systematic review

N. Smidt; Willem J. J. Assendelft; H. Arola; Antti Malmivaara; S. Green; Rachelle Buchbinder; D.A.W.M. van der Windt; L.M. Bouter

AIM: To evaluate the available evidence of the effectiveness of physiotherapy for lateral epicondylitis of the elbow. METHOD: Randomised controlled trials (RCTs) identified by a highly sensitive search strategy in six databases in combination with reference checking. Two independent reviewers selected RCTs that included a physiotherapy intervention, patients with lateral epicondylitis, and at least one clinically relevant outcome measure. No language restrictions were made. Methodological quality was independently assessed by two blinded reviewers. A best evidence synthesis, including a quantitative and qualitative analysis, was conducted, weighting the studies with respect to their internal validity, statistical significance, clinical relevance, and statistical power. RESULTS: 23 RCTs were included in the review, evaluating the effects of lasertherapy, ultrasound treatment, electrotherapy, and exercises and mobilisation techniques. Fourteen studies satisfied at least 50% of the internal validity criteria. Except for ultrasound, pooling of data from RCTs was not possible because of insufficient data, or clinical or statistical heterogeneity. The pooled estimate of the treatment effects of two studies on ultrasound compared to placebo ultrasound, showed statistically significant and clinically relevant differences in favour of ultrasound. There is insufficient evidence either to demonstrate benefit or lack of effect of lasertherapy, electrotherapy, exercises and mobilisation techniques for lateral epicondylitis. CONCLUSIONS: Despite the large number of studies, there is still insufficient evidence for most physiotherapy interventions for lateral epicondylitis due to contradicting results, insufficient power, and the low number of studies per intervention. Only for ultrasound, weak evidence for efficacy was found. More better designed, conducted and reported RCTs are needed.


BMC Medical Research Methodology | 2006

Reproducibility of the STARD checklist: an instrument to assess the quality of reporting of diagnostic accuracy studies

N. Smidt; Anne Wilhelmina Saskia Rutjes; Danielle van der Windt; Raymond Ostelo; Patrick M. Bossuyt; Johannes B. Reitsma; L.M. Bouter; Henrica C.W. de Vet

BackgroundIn January 2003, STAndards for the Reporting of Diagnostic accuracy studies (STARD) were published in a number of journals, to improve the quality of reporting in diagnostic accuracy studies. We designed a study to investigate the inter-assessment reproducibility, and intra- and inter-observer reproducibility of the items in the STARD statement.MethodsThirty-two diagnostic accuracy studies published in 2000 in medical journals with an impact factor of at least 4 were included. Two reviewers independently evaluated the quality of reporting of these studies using the 25 items of the STARD statement. A consensus evaluation was obtained by discussing and resolving disagreements between reviewers. Almost two years later, the same studies were evaluated by the same reviewers. For each item, percentages agreement and Cohens kappa between first and second consensus assessments (inter-assessment) were calculated. Intraclass Correlation coefficients (ICC) were calculated to evaluate its reliability.ResultsThe overall inter-assessment agreement for all items of the STARD statement was 85% (Cohens kappa 0.70) and varied from 63% to 100% for individual items. The largest differences between the two assessments were found for the reporting of the rationale of the reference standard (kappa 0.37), number of included participants that underwent tests (kappa 0.28), distribution of the severity of the disease (kappa 0.23), a cross tabulation of the results of the index test by the results of the reference standard (kappa 0.33) and how indeterminate results, missing data and outliers were handled (kappa 0.25). Within and between reviewers, also large differences were observed for these items. The inter-assessment reliability of the STARD checklist was satisfactory (ICC = 0.79 [95% CI: 0.62 to 0.89]).ConclusionAlthough the overall reproducibility of the quality of reporting on diagnostic accuracy studies using the STARD statement was found to be good, substantial disagreements were found for specific items. These disagreements were not so much caused by differences in interpretation of the items by the reviewers but rather by difficulties in assessing the reporting of these items due to lack of clarity within the articles. Including a flow diagram in all reports on diagnostic accuracy studies would be very helpful in reducing confusion between readers and among reviewers.


Occupational and Environmental Medicine | 2006

Long term health complaints following the Amsterdam Air Disaster in police officers and fire‐fighters

Anja C. Huizink; Pauline Slottje; Anke B. Witteveen; Joost A. Bijlsma; J.W.R. Twisk; N. Smidt; I. Bramsen; W. van Mechelen; H.M. van der Ploeg; L.M. Bouter; Tjabe Smid

Background: On 4 October 1992, a cargo aircraft crashed into apartment buildings in Amsterdam, the Netherlands. Fire-fighters and police officers assisted with the rescue work. Objectives: To examine the long term health complaints in rescue workers exposed to a disaster. Methods: A historical cohort study was performed among police officers (nu200a=u200a834) and fire-fighters (nu200a=u200a334) who performed at least one disaster related task and reference groups of their non-exposed colleagues (nu200a=u200a634 and nu200a=u200a194, respectively). The main outcome measures included digestive, cardiovascular, musculoskeletal, nervous system, airway, skin, post-traumatic stress, fatigue, and general mental health complaints; haematological and biochemical laboratory values; and urinalysis outcomes. Results: Police officers and fire-fighters who were professionally exposed to a disaster reported more physical and mental health complaints, compared to the reference groups. No clinically relevant statistically significant differences in laboratory outcomes were found. Conclusions: This study is the first to examine long term health complaints in a large sample of rescue workers exposed to a disaster in comparison to reference groups of non-exposed colleagues. Findings show that even in the long term, and in the absence of laboratory abnormalities, rescue workers report more health complaints.


PharmacoEconomics | 2004

Cost effectiveness of interventions for lateral epicondylitis: results from a randomised controlled trial in primary care.

Ingeborg B. C. Korthals-De Bos; N. Smidt; Maurits W. van Tulder; Maureen Rutten-van Mölken; H.J. Adèr; Danielle van der Windt; Willem J. J. Assendelft; L.M. Bouter

AbstractObjective: Lateral epicondylitis is a common complaint, with an annual incidence between 1% and 3% in the general population. The Dutch College of General Practitioners in The Netherlands has issued guidelines that recommend a wait-and-see policy. However, these guidelines are not evidence based.n Design and setting: This paper presents the results of an economic evaluation in conjunction with a randomised controlled trial to evaluate the effects of three interventions in primary care for patients with lateral epicondylitis.n Patients and interventions: Patients with pain at the lateral side of the elbow were randomised to one of three interventions: a wait-and-see policy, corticosteroid injections or physiotherapy.n Main outcome measures and results: Clinical outcomes included general improvement, pain during the day, elbow disability and QOL. The economic evaluation was conducted from a societal perspective. Direct and indirect costs (in 1999 values) were measured by means of cost diaries over a period of 12 months. Differences in mean costs between groups were evaluated by applying non-parametric bootstrap techniques. The mean total costs per patient for corticosteroid injections were €430, compared with €631 for the wait-and-see policy and €921 for physiotherapy. After 12 months, the success rate in the physiotherapy group (91%) was significantly higher than in the injection group (69%), but only slightly higher than in the wait-and-see group (83%). The differences in costs and effects showed no dominance for any of the three groups. The incremental costutility ratios were (approximately): €7000 per utility gain for the wait-and-see policy versus corticosteroid injections; €12 000 per utility gain for physiotherapy versus corticosteroid injections, and €34 500 for physiotherapy versus the waitand- see policy.n Conclusions: The results of this economic evaluation provided no reason to update or amend the Dutch guidelines for GPs, which recommend a wait-and-see policy for patients with lateral epicondylitis.n


BMC Public Health | 2005

Epidemiological study air disaster in Amsterdam (ESADA): study design

Pauline Slottje; Anja C. Huizink; Jos W. R. Twisk; Anke B. Witteveen; Henk M. van der Ploeg; Inge Bramsen; N. Smidt; Joost A. Bijlsma; L.M. Bouter; Willem van Mechelen; Tjabe Smid

BackgroundIn 1992, a cargo aircraft crashed into apartment buildings in Amsterdam, killing 43 victims and destroying 266 apartments. In the aftermath there were speculations about the cause of the crash, potential exposures to hazardous materials due to the disaster and the health consequences. Starting in 2000, the Epidemiological Study Air Disaster in Amsterdam (ESADA) aimed to assess the long-term health effects of occupational exposure to this disaster on professional assistance workers.Methods/DesignEpidemiological study among all the exposed professional fire-fighters and police officers who performed disaster-related task(s), and hangar workers who sorted the wreckage of the aircraft, as well as reference groups of their non-exposed colleagues who did not perform any disaster-related tasks. The study took place, on average, 8.5 years after the disaster. Questionnaires were used to assess details on occupational exposure to the disaster. Health measures comprised laboratory assessments in urine, blood and saliva, as well as self-reported current health measures, including health-related quality of life, and various physical and psychological symptoms.DiscussionIn this paper we describe and discuss the design of the ESADA. The ESADA will provide additional scientific knowledge on the long-term health effects of technological disasters on professional workers.


Quality of Life Research | 2007

Health-related quality of life of firefighters and police officers 8.5 years after the air disaster in Amsterdam

Pau line Slottje; Jos W. R. Twisk; N. Smidt; Anja C. Huizink; Anke B. Witteveen; Willem van Mechelen; Tjabe Smid

BackgroundIn 1992 a cargo aircraft crashed into apartment buildings in Amsterdam. In the troublesome aftermath rumours emerged on potential toxic exposures and health consequences. The aim of this study is to assess the long-term impact of this disaster on the health-related quality of life (HRQoL) of professional assistance workers.MethodsHistoric cohort study, using questionnaires to assess occupational disaster exposure, HRQoL (SF36), and background variables, at on average 8.5xa0years post-disaster. Participating were the exposed professional firefighters (nxa0=xa0334) and police officers (nxa0=xa0834) who reported disaster-related task(s), and their non-exposed colleagues who did not report such tasks (nxa0=xa0194, and nxa0=xa0634, respectively).ResultsMultivariate logistic regression analysis showed that exposed workers reported a significantly lower physical HRQoL and vitality than non-exposed workers. Exposed police officers also reported a lower mental HRQoL. Among exposed workers, a lower HRQoL was reported significantly more often by workers who had a close one affected by the disaster; by firefighters who rescued people, cleaned-up, or witnessed the immediate disaster scene; and by police officers who supported the injured. Exposed police officers who perceived the disaster as ‘not bad’ reported a lower HRQoL less often than those to whom it was ‘the worst ever’.ConclusionsThis study demonstrates that professional disaster assistance workers are at risk for a lower HRQoL, even after years.


British Journal of Health Psychology | 2008

Post‐disaster physical symptoms of firefighters and police officers: Role of types of exposure and post‐traumatic stress symptoms

Pauline Slottje; Anke B. Witteveen; Jos W. R. Twisk; N. Smidt; Anja C. Huizink; Willem van Mechelen; Tjabe Smid

OBJECTIVESnTo examine the relationships between exposure to the air disaster in Amsterdam and multiple physical symptoms among firefighters and police officers, and to explore the role of post-traumatic stress symptoms (PTSS) herein.nnnDESIGNnHistoric cohort study.nnnMETHODSnOn average 8.5 years post-disaster, exposed professional firefighters (N=334) and police officers (N=834) and their nonexposed colleagues (N=194 and N=634, respectively) completed questionnaires on disaster exposure and current symptoms. Logistic regression with adjustment for background characteristics was used to compare exposed and nonexposed workers. PTSS were added to these models, as was the interaction between exposure and PTSS, to explore potential mediating and modifying effects, respectively.nnnRESULTSnExposed workers reported multiple physical symptoms significantly more often. Multiple physical symptoms seemed to have particularly affected the exposed firefighters who rescued people, and the exposed police officers who supported injured victims and workers, who were involved in the identification of or search for victims and human remains, who witnessed the immediate disaster scene or had a close one affected by the disaster. These exposure effects were essentially independent of PTSS, and no significant interactions between exposure and PTSS were found.nnnCONCLUSIONSnIn conclusion, the excess in post-disaster multiple physical symptoms in exposed workers could not be attributed to PTSS.


BMC Public Health | 2006

Attribution of physical complaints to the air disaster in Amsterdam by exposed rescue workers: an epidemiological study using historic cohorts

Pauline Slottje; N. Smidt; Jos W. R. Twisk; Anja C. Huizink; Anke B. Witteveen; Willem van Mechelen; Tjabe Smid

BackgroundIn 1992 a cargo aircraft crashed into a residential area of Amsterdam. A troublesome aftermath followed, with rumors on potential toxic exposures and health consequences. Health concerns remained even though no excess morbidity was predicted in retrospective risk evaluations. This study aimed to assess to what extent the rescue workers attribute long-term physical complaints to this disaster, including its aftermath, and to examine associations between such attribution and types of exposure and background variables.MethodsHistoric cohort study that collected questionnaire data on occupational disaster exposure, attribution of physical complaints, and background variables on average 8.5 years post-disaster. For the present study the workers who were exposed to the disaster were selected from the historic cohort, i.e. the professional firefighters (n = 334), police officers (n = 834), and accident and wreckage investigators (n = 241) who performed disaster-related tasks.ResultsAcross the three occupational groups, a consistent percentage (ranging from 43% to 49%) of exposed workers with long-term physical complaints attributed these to the disaster, including its aftermath. Those with more physical complaints attributed these to a stronger degree. Multivariate logistic regression analyses showed that attribution was significantly more often reported by firefighters who rescued people, and by police officers who reported the identification and recovery of or search for victims and human remains, clean-up, or security and surveillance of the disaster area; who witnessed the immediate disaster scene; who had a close one affected by the disaster; and who perceived the disaster as the worst thing that ever happened to them. Age, sex and educational level were not significantly associated with attribution.ConclusionThis study provides further cross-sectional evidence for the role of causal attribution in post-disaster subjective physical health problems. After on average 8.5 years, almost a third (32%) of all the exposed workers, and almost half (45%) of the exposed workers with physical complaints, attributed these complaints to the disaster, including its aftermath. The similarity of the results across the occupational groups suggests a general rather than an occupation-specific attribution process. Longitudinal studies are needed to determine whether causal disaster attribution leads to persistence of post-disaster complaints and health care utilization.

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L.M. Bouter

VU University Medical Center

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Willem J. J. Assendelft

Radboud University Nijmegen Medical Centre

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Tjabe Smid

VU University Medical Center

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H.C.W. de Vet

VU University Medical Center

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Jos W. R. Twisk

VU University Medical Center

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