The Delphi method was developed in the early 1950s by the RAND Corporation with the intention of attaining consensus of opinions from an expert panel. The Delphi method is based on the principle that forecasts (or decisions) from a structured group of individuals are more accurate than those from unstructured groups. The technique consists of consecutive rounds of consensus building interspersed with controlled feedback of information to panel participants. For each round, findings are qualitatively and/or quantitatively summarized. A foundational aspect of the process is that experts are encouraged to consider revising their earlier answers in response to replies from other panel members during subsequent rounds.
A modified-Delphi method was employed for the First Annual Lumbar Total Disc Replacement Summit expert panel, which included one anonymous round of electronic survey administration and one round involving a face-to-face meeting with presentation, discussion, and consensus building.
To inform the process, a comprehensive, structured literature review was conducted using PubMed, which focused on compiling all clinical and economic evidence for lumbar total disc replacement (TDR) for the treatment of degenerative disc disease (DDD). This evidence was supplemented with an additional review of the gray literature, including health technology assessments, guidelines, and US coverage policies. Searches were conducted between 2000 and 2015, with no restrictions on the level of evidence or publication status. Only English-language articles were reviewed.
For the first round of the process, a 51-item questionnaire was developed which was divided into four parts. The first part included background questions to characterize panel members, requesting information on experience with lumbar spine surgeries, and completion of lumbar fusion and TDR procedures. The second section focused on defining lumbar TDR as a standard of care, including questions such as selection criteria used, challenges and best practices in diagnosing lumbar DDD, and criteria for defining a standard of care. The third part included questions about procedural complications and solutions (e.g., complication risk for TDR vs. fusion, reasons for complications, and timing of complications). Finally, the last section characterized barriers to lumbar TDR utilization, asking participants to cite which types of barriers were most common in their practice, their perspectives on commonly cited rationale for TDR coverage denial by US commercial insurers, predicted use of lumbar TDR over time in their practice, and reflections on economic evidence. The questionnaire was comprised of a combination of open- and closed-ended questions. Questions eliciting agreement included dichotomous response options (yes/no; or agree/disagree) to simplify the consensus building process.
In total, 15 of 17 surgeons completed the questionnaire. A qualitative analysis was conducted to analyze responses to questions. Responses to closed-ended questions were compiled and graphically presented as percentages or top rankings. For open-ended questions, themes were derived from the responses and compiled for informational purposes to guide further discussions. The questionnaire responses were used to inform statements for the consensus process in the second round. Statements were typically a modification of the original question, reflecting new learnings from the first round of responses. Of the 51 items evaluated, 15 statements were prioritized for consensus building. Prioritization focused on critical topics, obtaining representation from different sections of the survey, likelihood of reaching consensus with live discussions, and items more relevant to coverage decisions. In some instances, statements were added into the second round that were not part of questions from the first round. Relevant information gathered from the survey that was not used for consensus building is provided in the findings of each session within this publication.
The second round of the Delphi process involved a 6-hour face-to-face meeting with 17 spine surgeons and one former payer medical director. All the participants who completed the survey also attended the in-person meeting. At the meeting, surgeons and researchers presented the results of the updated clinical and economic literature review for lumbar TDR. Meta-analyses, randomized controlled trials, observational studies, health technology assessments, and economic analyses were presented. After literature presentations, three themed sessions followed, with a series of statements targeted for consensus. Within each of these sessions, results of the first round of questions were presented to the panel. Unique surgeon moderators were assigned to each session, which involved presenting the results of the first round of responses from the electronic questionnaire, and facilitating discussions on each proposed statement to align and try to achieve consensus. Discussions led to revisions to the statements in real time. Because the survey was live and open, questions that resulted in lack of consensus prompted group discussion.
For each proposed statement, panel members undertook an anonymous voting process using voting cards, with 18 panellists having the opportunity to vote. For each voting session, only two response options were applicable; agree or disagree. In certain situations, where there was disagreement, a second definite vote was held after further discussions. Consensus was defined as reaching ≥90% agreement on the statement. For some statements, a voting process was not undertaken due to insufficient time for statement revisions.
In total, 11 consensus statements were derived at the end of the process. Consensus statements focused on the clinical (i.e., efficacy and safety) and economic evidence for lumbar TDR, as well as lumbar TDR being a standard of care in a selective population of patients with DDD, with relevance to coverage decisions. The panel reached 100% agreement on 10 of the 11 consensus statements, and 94% agreement on the one remaining statement. These consensus statements, with supporting evidence, are further discussed in the subsequent publications.