PubMed Health⌕ Search

Biomedical subjects

W J Assendelft

Publications and source records attributed to W J Assendelft.

At least 55 records · Page 3Linked to original sources
PubMed1999

[The practice of systematic reviews. IV. Pooling results from separate studies].

Meta-analysis comprises the analysis of the data gathered in a systematic review. Meta-analysis can be defined as the combination of pooling results of similar studies into one overall estimate of the effect on the one hand and the exploration of sources of heterogeneity between studies on the other. A general statistical model is available for pooling the estimates of various types of effect parameters. Pooling enables the estimation of the effect of an intervention or exposure as precisely as possible (with narrow confidence intervals) which allows detection of minor effects. The Mantel-Haenszel method is also an excellent method for pooling effect parameters of dichotomous outcomes. Pooling provides an efficient means of summarizing the available knowledge.

Data Interpretation, Statistical↗
PubMed1999

[The practice of systematic reviews. III. Evaluation of methodological quality of research studies].

The methodological quality of the primary studies included in a systematic review may influence its results and final conclusions. Methodological quality may be defined in various ways. Partially because of this there are many different assessment lists. The most important dimension of quality is internal validity, defined as the confidence that the design, performance and report of a trial prevent or reduce systematic errors (bias) in the outcomes. For only a limited number of internal validity items a relationship with bias has been proven in empirical studies: concealment of randomisation and blinding of patients and outcome assessors. Preferably, quality should be assessed by at least 2 assessors independently. There is no consensus whether assessment should be done blinded for authors, journal, results and conclusions. Internal validity can be incorporated into statistical pooling in various ways: as a selection criterion, to be used as weight or to hierarchically order studies in a presentation. Well-designed comparative studies are needed to provide clearer guidelines for methodological assessment in the future.

Bias↗
PubMed1999

[The practice of systematic reviews. II. Searching and selection of studies].

Structured searching and selection of studies is an important component of a systematic review. It is recommended to record the various steps in a protocol in advance. The thoroughness of the searching and selection will partially depend on the available resources, like manpower and funds. A search action should be based on an unequivocally formulated research or clinical question, that is operationalized into clear inclusion and exclusion criteria. The actual start of a search strategy is a search in preferably multiple databases like Medline and EMBASE-Excerpta Medica. Additional search actions can be performed in trial registers and printed indexes and by correspondence with experts and hand searching of journals. Storage of the search results in a bibliographic database is recommended. Various methodological problems may play a role in searching and selecting studies for a review: studies may selectively not be published, results are only partially presented in the publication, studies are selectively included in reference lists, and reviewers themselves may make systematic errors in the selection process.

Bias↗
PubMed1999

Effectiveness of exercise therapy in patients with osteoarthritis of the hip or knee: a systematic review of randomized clinical trials.

OBJECTIVE: To review the effectiveness of exercise therapy in patients with osteoarthritis (OA) of the hip or knee. METHODS: A computerized literature search of Medline, Embase, and Cinahl was carried out. Randomized clinical trials on exercise therapy for OA of the hip or knee were selected if treatment had been randomly allocated and if pain, self-reported disability, observed disability, or patient's global assessment of effect had been used as outcome measures. The validity of trials was systematically assessed by independent reviewers. Effect sizes and power estimates were calculated. A best evidence synthesis was conducted, weighting the studies with respect to their validity and power. RESULTS: Six of the 11 assessed trials satisfied at least 50% of the validity criteria. Two trials had sufficient power to detect medium-sized effects. Effect sizes indicated small-to-moderate beneficial effects of exercise therapy on pain, small beneficial effects on both disability outcome measures, and moderate-to-great beneficial effects according to patient's global assessment of effect. CONCLUSION: There is evidence of beneficial effects of exercise therapy in patients with OA of the hip or knee. However, the small number of good studies restricts drawing firm conclusions.

Exercise Therapy↗
PubMed1998

Effectiveness of treatments for infantile colic: systematic review.

OBJECTIVE: To evaluate the effectiveness of diets, drug treatment, and behavioural interventions on infantile colic in trials with crying or the presence of colic as the primary outcome measure. DATA SOURCES: Controlled clinical trials identified by a highly sensitive search strategy in Medline (1966-96), Embase (1986-95), and the Cochrane Controlled Trials Register, in combination with reference checking for further relevant publications. Keywords were crying and colic. STUDY SELECTION: Two independent assessors selected controlled trials with interventions lasting at least 3 days that included infants younger than 6 months who cried excessively. DATA SYNTHESIS: Methodological quality was assessed by two assessors independently with a quality assessment scale (range 0-5). Effect sizes were calculated as percentage success. Effect sizes of trials using identical interventions were pooled using a random effects model. RESULTS: 27 controlled trials were identified. Elimination of cows' milk protein was effective when substituted by hypoallergenic formula milks (effect size 0.22 (95% confidence interval 0.09 to 0.34)). The effectiveness of substitution by soy formula milks was unclear when only trials of good methodological quality were considered. The benefit of eliminating cows' milk protein was not restricted to highly selected populations. Dicyclomine was effective (effect size 0.46 (0.33 to 0.60)), but serious side effects have been reported. The advice to reduce stimulation was beneficial (effect size 0.48 (0.23 to 0.74)), whereas the advice to increase carrying and holding seemed not to reduce crying. No benefit was shown for simethicone. Uncertainty remained about the effectiveness of low lactose formula milks. CONCLUSIONS: Infantile colic should preferably be treated by advising carers to reduce stimulation and with a one week trial of a hypoallergenic formula milk.

Animals↗
PubMed1998

[Effectiveness of manipulative therapy in low back pain: systematic literature reviews and guidelines are inconclusive].

In the Dutch general practitioners' guidelines spinal manipulative therapy (SMT) is not recommended for treatment of acute low back pain. This is in contrast to the recent American and English guidelines, which explicitly recommend SMT for this indication. Randomized clinical trials (RCTs) on SMT are on average of low methodological quality. Most systematic reviews, however, lead to positive conclusions. The potential sources of discrepancy between the recommendations in the national guidelines are: interpretation of the available RCTs and systematic reviews, composition of the guideline-setting committee, values of the participants and appreciation of direct and indirect costs. Definite conclusions on the efficacy of SMT for (acute) low back pain cannot yet be drawn. Therefore, more RCTs in various settings and on different indications are clearly needed.

Guidelines as Topic↗
PubMed1998

Insulin and risk of cardiovascular disease: a meta-analysis.

BACKGROUND: Our purposes were to estimate the strength of the longitudinal relationship between hyperinsulinemia and cardiovascular diseases (CVD) from the available literature and to identify study characteristics that modify this relationship. METHODS AND RESULTS: Articles were identified by means of a MEDLINE and Embase search and citation tracking. Eligible studies were prospective population-based cohort studies and nested case-control studies on the relationship between, on the one hand, fasting or nonfasting insulin levels and, on the other hand, myocardial infarction, death from coronary heart disease, and/or ECG abnormalities. Data were extracted pertaining to insulin measurements, type of outcome studied, adjustment for confounding, sex, mean age of the study population, follow-up period, insulin assay, and ethnic background (white or nonwhite). Associations of insulin and CVD were reexpressed in a uniform manner, an estimate of relative risk (RR) and 95% CI, to be used in meta-regression analyses. Twelve of 17 potentially eligible articles provided sufficient information. Overall, a weak positive association was found. The meta-analysis resulted in an estimated summary RR (95% CI) of 1.18 (1.08 to 1.29) for differences in insulin level, equivalent to the difference between the 75th and the 25th percentiles of the general population in The Netherlands. Ethnic background and type of insulin assay modified the relationship between insulin and CVD with borderline significance. CONCLUSIONS: Hyperinsulinemia is a weak risk indicator for the occurrence of CVD. The relationship between hyperinsulinemia and CVD was modified by ethnic background and by the type of insulin assay involved.

Aged↗
PubMed1997

Reliability of lumbar spine radiograph reading by chiropractors.

STUDY DESIGN: An intraobserver and interobserver study on the reproducibility of data was performed. OBJECTIVES: This study investigates the variability in the interpretation of lumbar spine radiographs by chiropractors working in private practice. SUMMARY OF BACKGROUND DATA: In chiropractic practice radiographs are used often, but this use is currently under debate. Therefore, there is a need for further study of the value of diagnoses made by radiographs by chiropractors. An acceptable intra- and interobserver agreement in radiograph reading is a prerequisite for a useful application of radiographs as a diagnostic tool in daily practice and in research. METHODS: Four chiropractors read 100 blinded sets of standard, erect anteroposterior and lateral lumbar radiographs independently. The same set was read in two separate sessions with a 2-month interval. The first session revealed the interobserver agreement. The comparison of the ratings by the same assessor in the two sessions indicated the intraobserver agreement. The assessors used a specially developed criteria list with emphasis on "nonspecific" radiographic findings. The prevalence of some important categories was increased artificially. Agreement was expressed in percentage agreement and generalized kappa, combining the results of all four assessors. RESULTS: Most kappas ranged from 0.40 to 0.75, representing fair to good agreement. In general, intraobserver agreement was better than interobserver agreement. The low kappas that were found may be explained partially by the high-agreement-low-kappa paradox as a result of a low prevalence. CONCLUSION: The kappas and percentage agreement were acceptable, although not excellent. These results will be beneficial for future research on the value of radiograph diagnosis of nonspecific findings for delivery of safe and effective chiropractic therapy.

Adult↗
PubMed1997

Spinal radiographic findings and nonspecific low back pain. A systematic review of observational studies.

STUDY DESIGN: A systematic review of published observational studies. OBJECTIVES: To examine the causal relationship between radiographic findings and nonspecific low back pain. SUMMARY OF BACKGROUND DATA: The causal relationship between radiographic findings and nonspecific low back pain still is controversial. METHODS: Two reviewers independently scored the methodologic quality of all relevant, available studies using a standardized set of criteria. The association between radiographic findings and nonspecific low back pain was expressed as an odds ratio with a corresponding 95% confidence interval. RESULTS: Degeneration, defined by the presence of disc space narrowing, osteophytes, and sclerosis, turned out to be associated with nonspecific low back pain with odds ratios ranging from 1.2 to 3.3. Spondylolysis and spondylolisthesis, spina bifida, transitional vertebrae, spondylosis, and Scheuermann's disease did not appear to be associated with low back pain. The validity scores of the observational studies ranged from 0% to 91% of the maximum score. Only two studies used a prospective design, and most studies lacked control for confounding, an appropriate test for nonspecific low back pain, and blinded assessment of radiographs and low back pain status. CONCLUSIONS: There is no firm evidence for the presence or absence of a causal relationship between radiographic findings and nonspecific low back pain.

Evaluation Studies as Topic↗
PubMed1997

A systematic review on the treatment of giardiasis.

To assess the efficacy of treatment of parasitological excretion of cysts and trophozoites and symptoms of patients with giardiasis, a systematic review of published randomized clinical trials was conducted through extensive searches in Medline, Embase and Current Contents from 1966 till 1996 as well as manual reviews of 28 journals. The methodological quality of all trials was assessed by guidelines of the Cochrane Collaboration. Thirty-one trials were included, only one of which had no serious methodological flaws. The mean score of parasitological examination was 4.8 out of a possible 15. There was a considerable effect in cure rate of treatment versus placebo (odds 9.3, 95% CI 4.69-18.4), but all 3 trials in this comparison had serious flaws. Metronidazole treatment over more than 3 days seems to achieve a better parasitological cure rate than other long treatment courses (pooled odds 2.6, 95% 1.7-3.8), but trials are clinically and statistically heterogeneous. Single-dose therapy is as effective as longer treatment courses (pooled odds 0.67, 95% 0.31-1.44). Within the single-dose regimens tinidazole (2 g) reaches a higher parasitological cure rate than other short therapies (pooled odds 55, 95% CI 3.7-8.3) with relatively few side-effects. Placebo-controlled trials with parasitological and clinical outcomes are needed.

Antiprotozoal Agents↗
PubMed1996

Spinal manipulation for low back pain. An updated systematic review of randomized clinical trials.

STUDY DESIGN: Systematic review of randomized clinical trials. OBJECTIVES: To assess the efficacy of spinal manipulation for patients with low back pain. SUMMARY OF BACKGROUND DATA: The management of low back pain remains controversial. Spinal manipulation is a widely used treatment option for low back pain. Recently issued clinical guidelines suggest that spinal manipulation may be effective for patients with acute low back pain. METHODS: A computer-aided search for published papers was conducted, and the methods of the studies identified were assessed. Scores were assigned for quality of methods (based on four main categories: study population, interventions, measurement of effect, and data presentation and analysis), the conclusion of authors regarding spinal manipulation, and the results based on the main outcome measure. RESULTS: Thirty-six randomized clinical trials comparing spinal manipulation with other treatments were identified. The highest score of a trial was 60 points (maximum score was set at 100 points), indicating that most were of poor quality. Nineteen studies (53%) showed favorable results for manipulation. In addition, five studies (14%) reported positive results in one or more subgroups only. Among the five studies with 50-60 points, three were positive, and two were positive only for a subgroup of the study population. Eleven trials compared manipulation with some placebo therapy, with inconsistent results. There appeared to be no clear relation between the methodologic score and the overall outcome of the studies. Twelve trials included patients with acute low back pain only. Of these, five reported positive results, four reported negative results, and three reported positive results in a subgroup of the study population only. There were eight trials comparing manipulation with other conservative treatment modalities, focusing on patients with subacute or chronic low back pain. Of these, five reported positive results, two reported negative results, and in one study no conclusion was presented. There were only 16 studies that included an effect measurement of at least 3 months. In only six of these do the authors report positive effects of manipulation. CONCLUSIONS: The efficacy of spinal manipulation for patients with acute or chronic low back pain has not been demonstrated with sound randomized clinical trials. There certainly are indications that manipulation might be effective in some subgroups of patients with low back pain. These impressions justify additional research efforts on this topic. Methodologic quality remains a critical aspect that should be dealt with in future studies.

Chiropractic↗
PubMed1996

Complications of spinal manipulation: a comprehensive review of the literature.

BACKGROUND: Spinal manipulative therapy (SMT) is a frequently applied therapy for back and neck pain. Serious complications of SMT are presented primarily in case reports. Many patients seen by physicians also seek care from therapists applying manipulative techniques. Therefore, background information on the risks of SMT is essential for physicians. METHODS: Relevant case reports, surveys, and review articles were identified using a comprehensive search of online and bibliographical databases. For every case, a record was made of first author, publication year, country, age and sex of the patient, background of the manipulator, preexisting conditions, type of complication, and course of the complication. Based on case reports and surveys, an estimation was made of the risk for the most frequently reported complications: vertebrobasilar accidents (VBAs) and cauda equina syndrome (CES). RESULTS: We derived 295 complications of spinal manipulations from the literature: 165 VBAs; 61 cases with disc herniation or progression to CES; 13 cerebral complications other than VBAs; and 56 other types of complications. The average age of patients with VBA was 38 years. Vertebrobasilar accidents occur mainly after a cervical manipulation with a rotatory component. Estimates of VBA range from 1 per 20,000 patients to 1 per 1 million cervical manipulations. The incidence of CES is estimated to be less that 1 per 1 million treatments. CONCLUSIONS: It is difficult to estimate the incidence of SMT complications, as they are probably underreported in the literature. Most non-VBA complications can be prevented by excluding patients with contraindications for SMT. Patients who develop complications such as CES should be treated as soon as possible. VBAs, however, are difficult to prevent and treat. Referral for SMT should not be made to practitioners applying rotatory cervical manipulation. Information about the risk of VBA should be included in an informed consent procedure for cervical manipulation with thrust techniques.

Back Pain↗
PubMed1996

Corticosteroid injections for lateral epicondylitis: a systematic overview.

BACKGROUND: Lateral epicondylitis (tennis elbow) is a common complaint, for which corticosteroid injections are a frequently applied therapy. However, there were no up-to-date reviews available that systematically addressed the effectiveness and adverse effects, including questions concerning optimal timing of injections and composition of the injection fluid. AIM: The aim of the study was to assess the effectiveness of corticosteroid injections in the treatment of lateral epicondylitis (tennis elbow) by systematic review of the available randomized clinical trials. DATA SOURCES: The data sources used were randomized clinical trials identified by literature searches of the MedLine (1966-1994) and Embase (Exerpta Medica) (1980-1994) databases for the keywords epicondylitis, tendinitis and elbow, injection. References given in relevant publications were further examined. STUDY SELECTION: The criteria for selecting studies were as follows: randomized clinical trials (treatment allocation in random or alternate order); one of the treatments to include one or more corticosteroid injections (additional interventions were allowed); participants suffering from lateral epicondylitis; and publication in English, German or Dutch. Abstracts and unpublished studies were not included. DATA SYNTHESIS: Methodological quality was assessed by means of a standardized criteria list (range 1-100 points). The extracted outcomes were the general conclusion drawn by the authors of the reports on the trials, and the success rates at the various follow-up points as (re)calculated by us. The success rates were subsequently graphically displayed and statistically pooled. Separate stratified analyses were conducted according to a predetermined analysis plan. RESULTS: Twelve randomized clinical trials were identified. The median methodological score was 40 points, indicating an overall poor to moderate quality. The pooled analysis indicated short-term effectiveness (2-6 weeks): pooled odds ratio (OR) = 0.15 [95% confidence interval (CI) 0.10-0.23], chi 2 [degrees of freedom (df = 5) = 13.3], indicating statistical heterogeneity. At longer term follow-up, no difference could be detected. The studies of better methodological quality indicated more favourable results than those of lesser methodological quality. The most suitable corticosteroid to use as well as dosage, injection interval and injection volume could not be derived from the various trials. CONCLUSION: The existing evidence on corticosteroid injections for the treatment of tennis elbow is not conclusive. Many trials were conducted in a secondary care setting and clearly had serious methodological flaws, and there was statistical heterogeneity among the trials. Corticosteroid injections appear to be relatively safe and seem to be effective in the short term (2-6 weeks). Although the treatment seems to be suitable for application in general practice, further trials in this setting are needed. As yet, questions regarding the optimal timing, dosage, injection technique and injection volume remain unanswered.

Adrenal Cortex Hormones↗
PubMed1996

The effectiveness of chiropractic for treatment of low back pain: an update and attempt at statistical pooling.

OBJECTIVE: To determine the effectiveness of chiropractic treatment for patients with low back pain by means of a systematic review of the literature. DATA SOURCES: Randomized clinical trials (RCTs) on chiropractic were identified with a Medline and Embase search (1966-1995), by citation tracking, and by hand searching of the relevant chiropractic reference systems (CRAC and Index to Chiropractic Literature). STUDY SELECTION: All RCTs on low back pain that involved chiropractors as therapists. DATA EXTRACTION: Methodological quality was assessed independently by two reviewers on 14 items covering internal validity, informativeness and study size. Data were extracted on: patients (initial referral, duration of complaints, radiation of pain); outcomes (four different types); and timing of follow-up (short-term, intermediate and long-term). Statistical pooling was intended, according to a preset analysis plan, to include subgroup analysis. DATA SYNTHESIS: Eight RCTs were identified. All RCTs had serious flaws in their design, execution and reporting. Because of the great variety of outcome measures and follow-up timing, there was insufficient data to enable statistical pooling of the RCTs. A narrative review, however, did not provide convincing evidence for the effectiveness of chiropractic for acute or chronic low back pain. CONCLUSIONS: There is certainly a need for correctly executed trials. In future research on the effectiveness of chiropractic, guidelines for uniform execution and reporting of RCTs should first be established to enable subsequent statistical pooling in systematic reviews of chiropractic trials.

Chiropractic↗
PubMed1995

The relationship between methodological quality and conclusions in reviews of spinal manipulation.

OBJECTIVE: To study the relationship between the methodological quality and other characteristics of reviews of spinal manipulation for low back pain on the one hand and the reviewers' conclusions on the effectiveness of manipulation on the other hand. DATA SOURCES: Reviews identified by MEDLINE search, citation tracking, library search, and correspondence with experts. STUDY SELECTION: English- or Dutch-language reviews published up to 1993 dealing with spinal manipulation for low back pain that include at least two randomized clinical trials (RCTs). DATA EXTRACTION: Methodological quality was assessed using a standardized criteria list applied independently by two assessors (range, 0% to 100%). Other extracted characteristics were the comprehensiveness of the search, selective citation of studies, language, inclusion of non-RCTs, type of publication, reviewers' professional backgrounds, and publication in a spinal manipulation journal or book. The reviewers' conclusions were classified as negative, neutral, or positive. DATA SYNTHESIS: A total of 51 reviews were assessed, 17 of which were neutral and 34 positive. The methodological quality was low, with a median score of 23%. Nine of the 10 methodologically best reviews were positive. Other factors associated with a positive reviewers' conclusion were review of spinal manipulation only, inclusion of a spinal manipulator in the review team, and a comprehensive literature search. CONCLUSIONS: The majority of the reviews concluded that spinal manipulation is an effective treatment for low back pain. Although, in particular, the reviews with a relatively high methodological quality had a positive conclusion, strong conclusions were precluded by the overall low quality of the reviews. More empirical research on the review methods applied to other therapies in other professional fields is needed to further explore our findings about the factors related to a positive reviewers' conclusion.

Humans↗