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Biomedical subjects

K Dickersin

Publications and source records attributed to K Dickersin.

At least 37 records · Page 2Linked to original sources
PubMed1994

Full publication of results initially presented in abstracts. A meta-analysis.

OBJECTIVES: To estimate the rate of full publication of the results of randomized clinical trials initially presented as abstracts at national ophthalmology meetings in 1988 and 1989; and to combine data from this study with data from similar studies to determine the rate at which abstracts are subsequently published in full and the association between selected study characteristics and full publication. DATA SOURCES: Ophthalmology abstracts were identified by review of 1988 and 1989 meeting abstracts for the Association for Research in Vision and Ophthalmology and the American Academy of Ophthalmology. Similar studies were identified either from reports contained in our files or through a MEDLINE search, which combined the textword "abstract" with "or" statements to the Medical Subject Headings ABSTRACTING & INDEXING, CLINICAL TRIALS, PEER REVIEW, PERIODICALS, MEDICAL SOCIETIES, PUBLISHING, MEDLINE, INFORMATION SERVICES, and REGISTRIES. STUDY SELECTION: Ophthalmology abstracts were selected from the meeting proceedings if they reported results from a randomized controlled trial. For the summary study, similar studies were eligible for inclusion if they described followup and subsequent full publication for a cohort of abstracts describing the results of any type of research study. All studies had to have followed up abstracts for at least 24 months to be included. DATA EXTRACTION: Authors of ophthalmology abstracts were contacted by letter to ascertain whether there was subsequent full publication. Other information, including characteristics of the study design possibly related to publication, was taken from the abstract. For the summary study, rates of full publication were taken directly from reported results, as were associations between study factors (ie, "significant" results and sample size) and full publication. DATA SYNTHESIS: Sixty-six percent (61/93) of ophthalmology abstracts were published in full. Combined results from 11 studies showed that 51% (1198/2391) of all abstracts were subsequently published in full. Full publication was weakly associated with "significant" results and sample size above the median. CONCLUSIONS: Approximately one half of all studies initially presented in abstract form are subsequently published as full-length reports. Most are published in full within 2 years of appearance as abstracts. Full publication may be associated with "significant" results and sample size.

Abstracting and Indexing↗
PubMed1993

Publication bias: the problem that won't go away.

Conclusions about the efficacy and safety of medical interventions are based on data presented in the scientific literature. The validity of these conclusions is threatened if publication bias results from investigators or editors making decisions about publishing study results on the basis of the direction or strength of the study findings. This paper reports meta-analyses performed using data from four prospective investigations in which a total of 997 initiated studies were followed to learn of study results, publication status, and reasons for nonpublication. The analysis indicates that there is a positive association between "significant" study results and publication (OR = 2.88; 95% confidence interval [CI] 2.13 to 3.90). When the analysis was restricted to controlled trials (n = 280), an even stronger relationship between "significant" results and publication was observed (OR = 6.15; 95% CI 2.24 to 16.92), with randomized trials (n = 200) apparently no less susceptible to publication bias than controlled trials in general (OR = 8.72; 95% CI 1.91 to 39.81). In every case, failure to publish was investigator-based, and not due to editorial decisions. The results of clinical trials should not be suppressed in this way. Development of registration systems for randomized trials is essential if this problem is to be minimized in future.

Bias↗
PubMed1993

NIH clinical trials and publication bias.

OBJECTIVE: To investigate the association between trial characteristics, findings, and publication. The major factor hypothesized to be associated with publication was "significant" results, which included both statistically significant results and results assessed by the investigators to be qualitatively significant, when statistical testing was not done. Other factors hypothesized to have a possible association with publication were funding institute, funding mechanism (grant versus contract versus intramural), multicenter status, use of comparison groups, large sample size, type of control (parallel versus nonparallel), use of randomization and masking, type of analysis (by treatment received versus by treatment assigned), and investigator sex and rank. DESIGN: Follow-up, by 1988 interview with the principal investigator or surrogate, of all clinical trials funded by the National Institutes of Health (NIH) in 1979, to learn of trial results and publication status. POPULATION: Two hundred ninety-three NIH trials, funded in 1979. MAIN OUTCOME MEASURE: Publication of clinical trial results. RESULTS: Of the 198 clinical trials completed by 1988, 93% had been published. Trials with "significant" results were more likely to be published than those showing "nonsignificant" results (adjusted odds ratio [OR] = 12.30; 95% confidence interval [CI], 2.54 to 60.00). No other factor was positively associated with publication. Most unpublished trials remained so because investigators thought the results were "not interesting" or they "did not have enough time" (42.8%). Metaanalysis using data from this and 3 similar studies provided a combined unadjusted OR of 2.88 (95% CI, 2.13 to 3.89) for the association between significant results and publication. CONCLUSIONS: Even when the overall publication rate is high, such as for trials funded by the NIH, publication bias remains a significant problem. Given the importance of trials and their utility in evaluating medical treatments, especially within the context of metaanalysis, it is clear that we need more reliable systems for maintaining information about initiated studies. Trial registers represent such a system but must receive increased financial support to succeed.

Clinical Trials as Topic↗
PubMed1993

Systematic literature review for clinical practice guideline development.

The purpose of this paper was to evaluate the quality and scope of the published literature on functional impairment due to cataract in adults as reviewed for the Agency for Health Care Policy and Research Clinical Practice Guideline. We examined the method of literature retrieved and analysis performed in the course of development of literature-based recommendations for the guideline panel. To collect data, we reviewed the process of literature acquisition and identification and the quality assessments made by reviewers of 14 individual topics composed of 77 issues related to the guideline. We collated this information to provide an assessment of the quality and scope of the relevant literature. Less than 4% (310) of the approximately 8,000 articles initially identified as potentially relevant to the guideline were ultimately used. The majority covered three topics (surgery and complication, 100; Nd:YAG capsulotomy, 77; and potential vision testing, 40). Three other topics--indications for surgery, preoperative medical evaluation, and rehabilitation--were devoid of articles meeting inclusion criteria. For 43 issues, there was no identifiable relevant literature. With few exceptions, the quality of the literature was rated fair to poor owing to major flaws in experimental design. Case series (256 reports) of one type or another accounted for the majority of the included literature. There were 17 random controlled trials. This review revealed a sparse and generally low-quality literature relevant to the management of functional impairment due to cataract, despite a relatively large data base in reputable peer-reviewed journals.

Adult↗
PubMed1992

Factors influencing publication of research results. Follow-up of applications submitted to two institutional review boards.

OBJECTIVE: --To investigate factors associated with the publication of research findings, in particular, the association between "significant" results and publication. DESIGN: --Follow-up study. SETTING: --Studies approved in 1980 or prior to 1980 by the two institutional review boards that serve The Johns Hopkins Health Institutions--one that serves the School of Medicine and Hospital and the other that serves the School of Hygiene and Public Health. POPULATION: --A total of 737 studies were followed up. RESULTS: --Of the studies for which analyses had been reported as having been performed at the time of interview, 81% from the School of Medicine and Hospital and 66% from the School of Hygiene and Public Health had been published. Publication was not associated with sample size, presence of a comparison group, or type of study (eg, observational study vs clinical trial). External funding and multiple data collection sites were positively associated with publication. There was evidence of publication bias in that for both institutional review boards there was an association between results reported to be significant and publication (adjusted odds ratio, 2.54; 95% confidence interval, 1.63 to 3.94). Contrary to popular opinion, publication bias originates primarily with investigators, not journal editors: only six of the 124 studies not published were reported to have been rejected for publication. CONCLUSION: --There is a statistically significant association between significant results and publication.

Academic Medical Centers↗
PubMed1990

A cohort study of summary reports of controlled trials.

Substantial numbers of clinical trials continue to be reported only in summary reports that present insufficient methodological details to permit informed judgments about the likely validity of the conclusions. Using a cohort of 176 controlled trials reported in summary form, we tested the hypotheses that they would be more likely to be followed by full reports if, on the basis of the information provided in the summary report, (1) the trial was judged to be methodologically sound, (2) the results favored the test treatment, and (3) the sample size was relatively large. The results of univariate and multivariate analyses provided support for only the third of these hypotheses. Investigators, as well as those who fund and sanction the conduct of clinical research, should make greater efforts to ensure that clinical trials are reported properly.

Clinical Trials as Topic↗
PubMed1990

The existence of publication bias and risk factors for its occurrence.

Publication bias is the tendency on the parts of investigators, reviewers, and editors to submit or accept manuscripts for publication based on the direction or strength of the study findings. Much of what has been learned about publication bias comes from the social sciences, less from the field of medicine. In medicine, three studies have provided direct evidence for this bias. Prevention of publication bias is important both from the scientific perspective (complete dissemination of knowledge) and from the perspective of those who combine results from a number of similar studies (meta-analysis). If treatment decisions are based on the published literature, then the literature must include all available data that is of acceptable quality. Currently, obtaining information regarding all studies undertaken in a given field is difficult, even impossible. Registration of clinical trials, and perhaps other types of studies, is the direction in which the scientific community should move.

American Medical Association↗
PubMed1990

Identification of meta-analyses. The need for standard terminology.

Our efforts to identify published articles describing meta-analyses of clinical trials illustrate the need for standard terminology to facilitate retrieval. We found 119 articles describing meta-analyses and eligible for inclusion in MEDLINE, and yet when we searched MEDLINE, using strategies based on textwords and medical subject headings (MeSH), only 48% of the 119 articles were identified. Sixty-eight (57%) of the 119 articles contained at least one of the terms "meta-analysis," "pooling," or "overview" in the title or abstract. The importance of meta-analyses in the evaluation of medical treatments argues for more disciplined use of a specific term in order to facilitate identification of articles. The fact that the National Library of Medicine has started in 1989 to index articles describing meta-analyses using the MeSH META-ANALYSIS underscores this argument.

Clinical Trials as Topic↗
PubMed1989

Retrospective and prospective identification of unpublished controlled trials: lessons from a survey of obstetricians and pediatricians.

Investigations in which statistically significant differences between treatment groups have not been observed are less likely than others to be reported in scientific journals. In clinical research, this selective suppression of "negative" results may lead to the adoption of ineffective or hazardous treatments. In an attempt to obtain information about unpublished trials in perinatal medicine, letters were sent to 42,000 obstetricians and pediatricians in 18 countries. As a result, we were notified of 395 unpublished randomized trials. Only 18 of the trials had been completed more than 2 years before the survey, a period during which at least 2300 reports of perinatal trials had been published. Of the 395 unpublished trials, 125 had ceased recruitment within the 2 years prior to the survey, 193 were actively recruiting at the time of the survey, and 59 were about to begin recruitment. It was concluded that publication bias will not be addressed successfully by attempts to obtain information about unpublished trials retrospectively. However, since the response rate to our request for details about ongoing and planned trials was good, prospective registration of trials at inception appears to be a feasible approach to reducing publication bias and its adverse consequences. An additional merit of prospective registration of clinical trials is that it should reduce unnecessary duplication (as opposed to necessary replication) in research and promote more effective collaboration.

Clinical Trials as Topic↗
PubMed1988

Report from the panel on the Case for Registers of Clinical Trials at the Eighth Annual Meeting of the Society for Clinical Trials.

A plenary session at the Eighth Annual Meeting of the Society for Clinical Trials addressed "The Case for Registers of Clinical Trials." There are a number of reasons for having registers of clinical trials: to promote collaboration and communication among investigators regarding new and ongoing clinical trials, to provide a basis for methodologic research, and to facilitate meta-analysis by the availability of a system of trial identification that is independent of the published literature. The experience gleaned by those involved with two existing trial registers, the International Committee on Thrombosis and Haemostasis Registry and the Oxford Database of Perinatal Trials, can be used to provide insight into the issues generic to trial registration. The time perspective to be used, inclusion and exclusion criteria, the practicability of comprehensive prospective registration, and funding are central considerations for these and other registers.

Clinical Trials as Topic↗
PubMed1987

Publication bias and clinical trials.

A study was performed to evaluate the extent to which the medical literature may be misleading as a result of selective publication of randomized clinical trials (RCTs) with results showing a statistically significant treatment effect. Three hundred eighteen authors of published trials were asked whether they had participated in any unpublished RCTs. The 156 respondents reported 271 unpublished and 1041 published trials. Of the 178 completed unpublished RCTs with a trend specified, 26 (14%) favored the new therapy compared to 423 of 767 (55%) published reports (p less than 0.001). For trials that were completed but not published, the major reasons for nonpublication were "negative" results and lack of interest. From the data provided, it appears that nonpublication was primarily a result of failure to write up and submit the trial results rather than rejection of submitted manuscripts. The results of this study imply the existence of a publication bias of importance both to meta-analysis and the interpretation of statistically significant positive trials.

Clinical Trials as Topic↗