Consensus building: The Delphi Method and the Nominal Group Technique

By Aina Pi, M.A., Consultant at Insights in Life Sciences (ilS).


Two of the best known methodologies to achieve consensus of opinion in expert panels or workshops are the Delphi Method and the Nominal Group Technique.

Both consensus techniques, widely used in the field of health, are a mean of collecting experts’ opinions where limited or conflicting evidence exists, and an approach of guiding health decision-making.

In practice, the Delphi method and the nominal group technique are frequently implemented to reach agreement on the classification of diagnostic criteria, the development of clinical guidelines, the identification of health professionals’ needs, as well as to orientate research.

The methodological manual for the development of Clinical Practices guidelines of the Spanish Ministry of Health1 states that these methods are particularly useful specifically if a general agreement on the formulation of recommendations is required: when there is a lack of scientific evidence, existing evidence is disputed, or when there is a little risk-benefit balance.

The Delphi method and the nominal group technique are described below:

Delphi method:

  • A Delphi study works as follow: An open-ended questionnaire about a particular topic is shared for an initial round of independent opinions from isolated respondents. The full range of opinions are summarized and distributed for several rounds of independent opinion and ranking, until a high degree of consensus is reached. Delphi studies usually consist of three to five rounds.
  • The Delphi method minimizes the influence of individuals and maximizes the reliability of results
  • The anonymity of the procedure allows to easily raise controversial issues
  • Since the exchange of information takes place via written documentation, no interactive discussion occurs. Nevertheless, the Delphi method can be adjusted for face-to-face meetings. In this regard, we have developed a “Delphi-like” methodology at ilS that counts with previous Interviews or Surveys, followed by Expert panels, known as ilS Knowledge(SM).
  • The Delphi method is very useful for international research since there is no need to gather all experts in the same location
  • The Delphi method requires an exhaustive prepared questionnaire, adequate time and high participant motivation since it involves a considerable workload for participants

The following case study, allows to gain a better understanding of how the Delphi method works:

Case study: Rationales behind the choice of administration form with fentanyl: Delphi survey among Danish general practitioners (GPs)2

  • The objective was to describe the rationale behind the choice of fentanyl (often used in the management of chronic pain) administration forms among Danish GPs.
  • An expert panel of 33 GPs collaborated in the study. In the first round, they wrote the main reasons for prescribing and not prescribing fentanyl patches, oral transmucosal systems, and nasal sprays. Their answers were summarized, and in two additional rounds of consultation, they were required to rate the importance of each reason.
  • As a result, a ranking of the most important rationales behind the choice of fentanyl administration form was obtained.

Nominal Group Technique:

  • The nominal group technique methodology works as follow: Participants meet in a session and complete a first round of independent opinions in writing about a particular topic along with its rationale. The results are summarized and distributed to participants. With the support of a moderator, participants expose and discuss their opinions for clarification and evaluation. Several rounds of independent opinions and ranking may be conducted. When the final round of ratings is carried out, the highest total positions are selected as the final decisions. Nominal Groups studies usually consist of four to five rounds
  • The Nominal Groups technique maximizes the compilation of information since all individuals inputs are considered, preventing people from dominating the discussion and encouraging minority views to be shared
  • It is a particularly useful technique since it gathers all experts at the same time and location, being a cost-effective and time efficient method
  • The Nominal Groups method requires an accurate pre-planning from the moderator and experts, and availability from experts since they are assembled together in a single session.


The following case study, allows to gain a better understanding of how the Nominal Group Technique works:

Case study: Identifying areas to improve pain management in hospitalized patients3

  • The objective was to identify the areas to prioritize interventions in the pain management for inpatients in a hospital from the USA
  • A multidisciplinary group of 27 health professionals participated in study.
  • In the first round, 94 ideas were generated. General and context-specific priority ideas were summarized and grouped into several categories. In the following rounds, participants were required to rate the importance of each idea.
  • Consequently, a ranking of the main priorities to improve pain control among hospitalized patients was set.

If you would like to gain further knowledge, you can explore the following case studies:

At ilS we are specialized in Primary Research in the Life Sciences field and we use both techniques for consensus building: the Delphi Method and the Nominal Group Technique while moderating Expert Panels. Based on our own experience accumulated during over 5 years, we have adapted those methodologies in order to make sure consensus is achieved in the most efficient manner for our Clients.



1Manual metodológico de elaboración de guías de práctica clínica en el Sistema Nacional de Salud. MSPS, 2007. Link

2Jacobsen R, Møldrup C, Christrup L. “Rationales behind the choice of administration form with fentanyl: Delphi survey among Danish general practitioners” Journal Opioid Management (2010);6(4):259-68. 

3Peña A, Estrada CA, Soniat D, Taylor B, Burton M. “Nominal group technique: a brainstorming tool for identifying areas to improve pain management in hospitalized patients” J Hosp Med. 2012;7(5):416-20.

2018-05-15T21:10:12+00:00 enero 19th, 2015|Market Research|