Health technology assessment (HTA) is an evidence-based, multistage process that assesses the clinical, economic and social impact of an increasingly wider range of medical interventions. HTA is applied to medicines, medical devices, diagnostics, nutrition and care services. The best available evidence is required for HTA to be relevant and valid – typically from randomised controlled trials and systematic reviews. The level and availability of evidence at the time of the HTA varies considerably; this can depend on the type of healthcare intervention, the stage of development, the exposure and use of the intervention, and the incidence of the health problem being assessed. Consequently, data gaps often arise that warrant the use of lower levels of evidence, including expert opinion.

External experts can be consulted at different stages of a HTA, for example, during the scoping stage to ensure that the research question captures the most relevant populations, outcomes and comparators for a given healthcare market and clinical context. Expert opinion can also be used as part of evidence synthesis and analysis if other evidence sources are lacking, for example, through the use of Delphi (consensus) exercises (1) and quantitative elicitation techniques (2). Such quantitative techniques can elicit the level of uncertainty around experts’ opinions, which can inform sensitivity analyses for health economic modelling. Indeed, expert opinion can be key when parameterising a health economic model, and is often required to inform inputs such as resource utilisation, standard of care and patients’ health states.

The findings from a recent literature review (3), which evaluated the guidelines and recommendations of 77 international HTA agencies, indicate that whilst some agencies do recognise and rely upon expert opinion to inform decision making, the practice is not ubiquitous. The authors noted that of the 22 agencies that reported using experts within the HTA process, the manner and extent of this expert involvement was heterogeneous. The authors concluded that ‘despite existing recommendations on the use of expert opinion in HTA, common standards for elicitation are scarce in HTA guidelines’.

HTA relies on the best available evidence and frequently this comes in the form of human beings who can bring key insights from a patient, clinician or commissioner perspective to the table. However, the data collection and analysis of expert opinion needs to be conducted and reported in a transparent and consistent way, both by industry and HTA agencies, for it to be reliable, credible, balanced and add true value to the HTA decision-making process.

At DRG Abacus, our HTA consultants can provide guidance and assistance to incorporate expert opinion into HTA using qualitative and quantitative approaches, be that during the early scoping phases or later validation steps of the process. Get in touch with our expert HTA consultants at to find out more.


  1. Hsu CC, Sandford The Delphi technique: making sense of consensus. Pract Assess Res Eval. 2007;12(10). Available at: [Last accessed March 2017].
  2. Grigore B, Peters J, Hyde C, Stein K. A comparison of two methods for expert elicitation in health technology assessments. BMC Med Res Methodol. 2016 Jul 26;16:85.
  3. Hunger T, Schnell-Inderst P, Sahakyan N, Siebert U. Using expert opinion in health technology assessment: a guideline review. Int J Technol Assess Health Care. 2016 Jan;32(3):131-9.

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