Systematic literature reviews (SLRs) are designed to synthesize published data exhaustively. However, even the most comprehensive searches can often uncover gaps in evidence. In such cases, supporting the findings with expert insights becomes important for a better understanding and contextualizing. Expert insights can offer practical wisdom on questions that just the evidence cannot answer, especially in emerging or under-researched domains where clinical judgment, practicability, or patient diversity play crucial roles.(1, 2)
Selection of the right experts is a meticulous task. This process should be transparent and criteria-based, focusing on the experts’ professional experience, academic credentials, and relevant contributions to the field. The panel should collectively reflect diversity across not just geography but also specialty and perspective. For Delphi or consensus-building exercises, 10-15 experts can facilitate statistical rigor, while smaller panels of 5-8 well-chosen experts can generate strong, qualitative insights without logistical difficulty. Expanding the search beyond close professional circles can help lower homogeneity, introducing a range of perspectives.(1-3)
The method of expert engagement relies on the type of information required. Qualitative methods, including semi-structured interviews or focus group discussions, are perfect for exploring in-depth themes and discovering the “why” behind some practices or opinions. Quantitative methods, such as structured surveys allow for aggregation and comparison across experts.(2-4) Delphi techniques, comprising iterative rounds of anonymous feedback, are especially important for obtaining consensus on difficult or uncertain topics. On the other hand, advisory boards, enable dynamic discussion and validation of primary findings, specifically for inferring results or developing recommendations.(5, 6)
Each methodology has unique strengths and trade-offs. Qualitative interviews identify nuances but can be subjective and harder to reproduce; whereas, quantitative tools enhance comparison but risk oversimplification. Delphi’s structured consensus process improves strength and transparency but needs time and commitment from participants. Advisory boards offer critical real-world insights but need careful moderation to avoid bias. Any method chosen maintaining a systematic audit trail, from expert selection to data analysis, can help ensure transparency and duplicability.(3-6)
Management of potential conflicts of interest is equally crucial. Experts often maintain academic or industry affiliations, which should be disclosed instead of automatically excluding participation. Balanced representation, independent facilitation, and transparent documentation of all inputs reinforce integrity. Supporting SLRs with expert insight should always improve, not surpass, the available evidence. It is best to present the published data first, then incorporate expert perspectives with precise rationale, clearly differentiating between empirical evidence and explanatory insight.(1-3)
Finally, the objective of integrating expert opinion into systematic evidence is to reach conclusions that are both scientifically robust and practically relevant. Careful selection of experts, transparent methodologies, and responsibly interpreted findings provide depth, relevance, and context to literature-based inferences. This amalgamation of data and experience facilitated evidence-based recommendations that are grounded in the realities of clinical and policy decision-making.
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References
- Janson E, Hines PA, Berntgen M, et al. Value Health. 2022; 25(10): 1726-1735.
- Nagavci B, Gáspár Z, Lakatos B. Defining expert opinion in clinical guidelines: insights from 98 scientific societies – a methodological study. BMC Med Res Methodol. 2025 Apr 2;25(1):87.
- Sekhon M, de Thurah A, Fragoulis GE, Schoones J, Stamm TA, Vliet Vlieland TPM, et al. Synthesis of guidance available for assessing methodological quality and grading of evidence from qualitative research to inform clinical recommendations: a systematic literature review. RMD Open. 2024;10:e004032.
- Eibling D, Fried M, Blitzer A, Postma G. Commentary on the role of expert opinion in developing evidence-based guidelines. Laryngoscope. 2014 Feb;124(2):355-7.
- Beiderback D, Frevel N, von der Gracht HA, et al. Preparing, conducting, and analyzing Delphi surveys: Cross-disciplinary practices, new directions, and advancements. MethodsX. 2021; 8:
- Nasa P, Jain R, Juneja D. Delphi methodology in healthcare research: How to decide its appropriateness. World J Methodol. 2021 Jul 20;11(4):116-129.