Systematic literature reviews (SLRs) serve as the gold standard for evidence synthesis, informing healthcare decisions. However, a pertinent question arises in the methodology of these reviews: should conference abstracts be included in the search for relevant studies? This query prompts a comprehensive examination of both the advantages and disadvantages, with the ultimate decision based on the specific goals of the SLR.[1]
Conference abstracts, often preceding full publications, provide timely access to critical information. This timeliness is especially vital in rapidly evolving fields, ensuring that SLRs stay current and offer an up-to-date perspective on the existing evidence landscape. Further, considering that not all conference abstracts are published in peer-reviewed journals, excluding abstracts translates to the exclusion of valuable data, compromising the comprehensiveness of the SLR.[1]
It is well known that SLRs that rely solely on published studies carry a risk of publication bias which can distort the overall treatment effect estimate. Publication bias arises out of the selective publication of studies with positive results. Including conference abstracts acts as a countermeasure to this, offering a more balanced representation of study outcomes, regardless of their direction. This inclusion contributes to a more nuanced understanding of the effectiveness of the intervention.[1]
Excluding conference abstracts that report early trial findings particularly randomized controlled trials (RCTs) from the evidence synthesis process introduces ethical concerns as well. Patient participation is grounded in the expectation that their contribution will contribute to scientific knowledge. The non-fulfillment of this commitment is viewed as an ethical problem, emphasizing the importance of including conference abstracts to honor the contributions of study participants. This ethical dimension adds a layer of responsibility to systematic reviewers, urging them to consider the broader implications of excluding conference abstracts.[1]
Conference abstracts frequently present findings with direct policy implications. Including them in SLRs ensures that policy decisions are informed by the latest and potentially impactful research. This alignment of SLR processes with real-world applications enhances the relevance and applicability of the synthesized evidence, making it a valuable resource for policymakers and healthcare practitioners. The advantages of including conference abstracts extend beyond the content they provide, contributing to a more dynamic and adaptive SLR process.[1]
However, the process of identifying relevant conferences, extracting abstracts, and sifting through extensive collections can be resource-intensive. Despite advancements like the inclusion of conference abstracts in searchable databases such as EMBASE, challenges persist. Abstracts, characterized by brevity, may lack essential information for systematic reviewers to comprehensively assess study design, methods, bias risk, outcomes, and results. The concise nature of abstracts poses a challenge for reviewers seeking a thorough understanding of the included studies. Additionally, the non-standard format of conference abstracts presents an additional layer of complexity, further complicating the extraction and evaluation process.[3]
Moreover, abstracts often lack peer review, and their preliminary nature may result in unreliable information. Discrepancies between abstracts and subsequent full publications, particularly in critical aspects such as methods and results, raise questions about the dependability of abstracts. While meta-epidemiologic studies have shown only minor differences in results between meta-analyses with and without conference abstracts, the inclusion of “gray” literature, including conference abstracts, may lead to shifts in significance levels or, in some cases, no substantial change.[3,4]
In conclusion, the decision to include conference abstracts in SLRs should be carefully considered. The advantages, including timeliness, addressing publication bias, ethical considerations, and informing policy decisions, underscore the potential benefits. However, challenges related to resource intensity, information adequacy, and reliability necessitate a nuanced approach. By adopting a flexible and evidence-driven strategy, systematic reviewers can harness the benefits of including conference abstracts without compromising the integrity of their synthesis efforts.
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References
- Hackenbroich S, Kranke P, Meybohm P, Weibel S. Include or not to include conference abstracts in systematic reviews? Lessons learned from a large Cochrane network meta-analysis including 585 trials. Systematic Reviews. 2022 Dec;11(1):1-0.
- Murad H, Smith J, Singh G, Deber R. Methodological and reporting quality of conference abstracts: a systematic review. J Clin Epidemiol. 2013;66(7):705-15.
- Cohen AM, Glazner JE, Roeder K, Sandvik L. Does inclusion of published abstracts of randomized controlled trials in systematic reviews affect risk ratio estimates? J Clin Epidemiol. 2014;67(7):796-802.
- Egger M, Davey SG, Davey A. Bias in the selection of conference abstracts for presentation. Lancet. 1997;349(9055):1069-70.