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International Dental Education |
Key words: publication, publication bias, case report
Submitted for publication 01/11/06; accepted 04/25/06
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Abstract |
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Case reports are widely used in dentistry to investigate clinical aspects or procedures that are not well known or not properly documented. They are especially useful in reporting complications or adverse events in individual patients or to propose the hypothesis that a subgroup of patients may react differently to an intervention.2 Case reports and case series of a novel treatment approach are studies that usually precede other more complex designs like well-conducted randomized clinical trials. Although they may be a good starting point to describe some clinical scenario, case reports are essentially qualitative and exploratory studies and are strongly subject to bias. The limited number of observations (a single patient), the lack of controls, and the subjectivity in interpreting outcomes usually minimize the validity of clinical inferences.
On the other hand, case reports have the potential to influence clinical decisions because they are patient-centered and deal with tangible outcomes (or benefits) that directly measure how a patient feels, functions, or survives.3 Case reports and case series are often the first line of evidence and likely to account for the greatest part of discarded treatments in medicine.4 Consequently, case reports have strong appeal to the dentist, particularly when clinical decision making is not aided by an evidence-based approach.
Scholey and Harrison5 recently stated that dental researchers need to be aware of the potential problems that arise from a specific kind of bias: publication, or positive-outcome, bias. That is defined as the tendency of investigators to submit, or reviewers and editors to accept, manuscripts based on the direction or strength of the study findings.5,6 This definition is based on the fact that studies with the most positive outcomes (or most successful results) are more likely to be published, with the related assumption that negative results are obtained in poor quality studies.7
The main problem associated with positive-outcome bias is that positive findings may potentially affect clinical practice, by encouraging dental practitioners and opinion-makers to choose presumed successful treatments or procedures without evidence of the likelihood of negative outcomes to occur. Therefore, the aim of this study was to identify the occurrence of positive-outcome bias of case reports published in Brazilian dental journals and to make a critical appraisal to access the methodological quality of these articles.
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Materials and Methods |
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A representative sample of twenty-eight dental journals and 564 issues of these journals was selected for the period of 1993 to 2003 (Table 1
). The issues included 5,453 articles that were classified in relation to study design according to previously defined criteria.
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After analysis, 1,064 (19.5 percent) of the original 5,453 articles were classified as case reports. A random sample of 50 percent of the screened articles that met inclusion criteria was selected (n=532). Those restricted to diagnostic procedures (n=97) were excluded because they usually do not achieve a clinical outcome as a result of an intervention. Hence, only interventional studies were included, resulting in a final sample of 435 case reports.
An evaluation instrument was constructed, and the 435 case reports were critically appraised by the same two raters using previously defined criteria, as follows:
A final question was included to detect a possible positive-outcome bias: "Does the case report clearly have a positive outcome, and was the intervention described as successful by the authors?"
All these items were distributed in twenty-five questions related to article title, abstract, introduction, case description, discussion, and conclusion. Three response categories were provided: 1) yes, 2) no, or 3) in part. Guidelines were also provided for each question to guide examiners’ appraisal. Descriptive analysis of data was done using SPSS 10.0 software.
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Results |
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. Analysis of data reveals that the formal structure of case reports described previously was followed in the majority of studies. Title, abstract, description of patient, clinical scenario and procedures, photographs, and conclusions were mostly appropriate or at least partially appropriate. On the other hand, some valuable information that might influence the decision making process of dental practitioners was often not provided.
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Due to limitations of the study design, case reports must be carefully appraised when clinical inferences are made. However, 80.7 percent of the reviewed articles did not mention any methodological restriction of study design (10.6 percent, yes). No potential variation of clinical outcomes was presented or discussed in 67.6 percent of the studies (23.4 percent, yes), and no restrictions of intervention were presented or discussed in 84.8 percent of the studies.
Structure of abstracts was partially appropriate in 85.3 percent of studies, objectives were explicit in approximately half of the studies (54.3 percent, yes; 37.2 percent, in part), and the patient’s description was adequate in 23.4 percent (69.4 percent, in part).
Considering the likelihood of positive-outcome bias, almost all studies reported favorable outcomes and successful interventions (99.1 percent). Only four studies (0.9 percent) did not reported successful outcomes after intervention. Patients abandoned treatment in two of these studies, and the outcome of the intervention was not described in the other two reports. It was observed that these four studies were not published intentionally to report negative outcomes because a positive outcome was assumed throughout the text. These findings strongly suggest that case reports are almost exclusively used by authors to report interventions with positive outcomes, which may be considered as a positive-outcome bias effect.
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Discussion |
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There is currently little research on publication bias in dentistry, though other areas of health care research have been aware of the potential problems that arise from the development of a biased pool of evidence.6,7,9,10 Assessments of publication rates of studies presented at scientific meetings have shown that positive outcome is one potential predictor of submission and publication of complete studies.11,12 Dickersin et al.13 observed in medical studies that investigations are more likely to be published when results are considered "significative" and null hypotheses rejected (OR=2.54; IC95%=1.63-3.94). Misakian and Bero14 analyzed studies on passive smoking and detected that median time for publication was five years (CI 95%= 4–7 years) for nonsignificant outcomes (p>0.05) and three years (CI 95%=3–5 years) for significant outcomes (p<0.05). Littner et al.15 verified that articles with negative results are more likely than articles with positive results to be published in journals with lower impact factors. Positive-outcome bias was also observed as a potential source of bias in systematic reviews and meta-analysis of randomized clinical trials.16–18
Publication bias has not been assessed in case reports except recently.4 These authors observed that case reports and case series are well received and have significant influence on subsequent literature and possibly on clinical practice. Overall, there is a strong publication bias favoring positive results, and opportunity should be created for publication of follow- up reports in controlled clinical trials.4
In the present study, a positive-outcome bias was evident. There was almost unanimous reporting of intervention success, and most studies did not report any skepticism about the effectiveness of the intervention under study. One can therefore assume that patients often do not participate in clinical decisions and that they are not fully informed about treatment alternatives, limitations, and potential variations in outcome. Follow-up information, even in short-term studies, was frequently not reported, which may decrease confidence in inferences about the effectiveness of interventions. Although declaration of commercial funding by authors has not been studied, investigators who were funded by dental companies or equipment suppliers may have implicit conflicts of interest. Therefore, when not properly managed, commercial support could contribute to increasing the risk of positive-outcome bias in case reports.
Our findings strongly suggest that case reports are almost exclusively used by authors to report interventions that result in positive outcomes, or, alternatively, journal editors fail to publish negative outcomes reported in case reports. On the other hand, it can be argued that conceptually all clinical data are of value, provided that the study design and procedures underlying the conclusions are well controlled and valid. As pointed out by Ashley,19 a negative outcome is only "negative" for the individual or organization that sponsored or had commercial interest in the investigation underlying the paper. If the study results in data that refutes an initial hypothesis, the publication of these data may not result in negative outcome for anyone. Indeed, the outcomes might be positive. Negative data can provide balance, indicate immaturity of knowledge, demonstrate that a line of research is not worth following, or reveal inadequate methodology, all of which are outcomes that the author and the publisher should be lauded for publishing.19
Our report does not intend to persuade dental practitioners and researchers to submit case reports with negative outcomes for publication. Journal editors should encourage reporting experiences of clinical success. However, poor reporting of important issues for clinical decision making may also dissuade readers from taking questioning postures on published studies. If authors have a deliberate intention of publishing only successful performances without considering multiple factors that can lead to failure, they might be contributing to a misleading notion of clinical success in dentistry.
Scientific journal reading is an important continuing educational activity. Finding and using published results to support professional decisions must be a systematic process, based on the principles of evidence-based practice. Therefore, how to decide whether to read and use an article that may be relevant to a clinical decision is part of continuing education for dental students and practitioners. The use of these strategies may improve the efficiency of readers for incorporating research results into their practice.
More studies are needed to assess the potential influence of positive-outcome bias on dental practitioners’ clinical decisions. Readers must be aware of this problem so they can critically judge the internal and external validity of studies and ultimately avoid exposure of patients to unnecessary and unjustified risks.
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Conclusion |
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Footnotes |
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REFERENCES |
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