5.1.3.2 Evidence from expert opinion

5.1.2.2.1 Definition

Expert Opinion: A view or judgement formed about something, not necessarily based on fact or knowledge; a statement of advice by an expert on a professional matter. ¹⁶

Expert opinion refers to a view or judgement formed about something, not necessarily based on fact from formal empirical evidence; or a statement of advice by an expert on a healthcare matter. In healthcare, common sources of expert opinion will be the repositories of learned colleges/bodies and opinion pieces in professional journals.

Proponents of evidence-based healthcare have, since the earliest days of its emergence, been brutally explicit in their rejection of opinion as a sound basis for decision-making. Sackett ¹⁹ is vehement in his rejection of the use of expert opinion in evidence-based healthcare and argues that ‘experts’ are often regarded as having a great deal of prestige and that their opinions possess a much:

“...greater persuasive power than they deserve on scientific grounds alone. Whether through deference, fear, or respect, others tend not to challenge them, and progress towards the truth is impaired in the presence of an expert.”^{19 (page 1283)}

Generally speaking, this view (or ‘opinion’) of Sackett is shared by a majority of those who are involved in the evidence-based healthcare movement.  Holmes ²⁰ argues that the emergence of the evidence-based medicine movement in the 1990s ranked randomized controlled trials “atop a hierarchy of scientific methods, with expert opinion situated at the bottom.”^{20 (page 11)} This rejection of expert opinion is seen as a source of evidence because expertise is difficult to define, and experts do not always agree with one another. He suggests that expert clinicians are often constrained by cognitive biases that cannot be overcome. Additionally it is asserted that reliance on expert opinion in decision-making “is not an unfortunate consequence of an underdeveloped Evidence Based Medicine (EBM) but a necessary requirement for optimal practice of clinical medicine.” ^{21(page 1188)}

Evidence from expert opinion differs in kind instead of in degree from evidence from randomized controlled trials²² and in contemporary practice, the now promoted ideal being an evidence-based practitioner rejects any deference to the clinical expert because expert opinion is seen as the last remnant of the ‘authoritarian’ model of clinical practice that EBM seeks to replace.²³

Accordingly, knowledge derived from reasoning related to pathophysiologic principles or unsystematic clinical experience is regarded as suspect. Whilst proponents of EBM assert that evidence-based practice includes the integration of the best available evidence with clinical judgement or experience and the patient’s goals and values, they do not explicitly acknowledge the value of pathophysiologic reasoning or of expert opinion as evidence in and of itself. Whilst an opinion is not a product of ‘good’ science it is, however, largely empirically derived and mediated through the cognitive processes of practitioners who have been typically trained in scientific method (and often draws on evidence from research). This is not to say that the superior quality of evidence derived from rigorous research is to be denied, but rather that in its absence it is not appropriate to discount expert opinion as non-evidence.

Opinion as Evidence

Evidence of generalities versus evidence of particularities

Proponents of the evidence-based practice movement originally envisioned a future when most, if not all, clinical decisions would be based on external, objective, and empirically derived evidence that supports particular courses of action.² However, expert opinion (based on accumulated knowledge from a wide range of sources including research) probably still constitutes the basis of many healthcare practices. ²⁴

The reality that there is often no solid evidence for much of the care delivered by healthcare professionals. ²⁵ Furthermore, there are few examples of evidence-based healthcare groups developing concrete plans for remedying this problem. This contemporary lack of serious thought and research into the substantive nature of expert knowledge/expertise and the role it plays in evidence-based healthcare, with its focus only on external evidence, represents a recognizable gap in knowledge nationally and internationally.² Although the importance of clinical expertise and judgment is acknowledged in mainstream evidence-based healthcare, it is not well understood in terms of the extent to which external, research-derived wisdom outweighs expertise in everyday clinical decision making from both a practitioner perspective and a patient/client perspective. Whilst patients/clients value the technically, scientifically informed practitioner who is also clinically wise, health professionals of all persuasions recognize that using evidence without clinical judgment, clinical reasoning or critical thinking falls far short of best practice. Thus, marrying the generalized evidence derived from research to the particular and singular evidence derived from individual patients/clients is anecdotally supported by patients/clients and health professionals, yet it is rarely discussed in evidence-based practice circles, and understandings of it are, as yet, poorly developed.

Expert opinion arises out of: “...the expert’s personal assessment of the validity of published reports, new knowledge learned at meetings and symposia, awareness of unpublished studies with “negative” results, and knowledge of the (often unreported) practice styles of colleagues in their field of expertise. The breadth and depth of such knowledge are often difficult to capture and may not be appreciated by those outside the field of expertise but are typically recognized by other domain experts. As in any human endeavour, fundamental conflicts often exist between the opinions of experts due to differences of interpretation. In healthy organizations, these conflicts lead to more in-depth exploration, hopefully including efforts to seek objective data to support one contention over another.”^{24 (page 356)}

Expert opinion as a legitimate source of evidence

There is a growing literature that argues for the recognition of opinion as a form of knowledge that should be afforded some legitimacy as evidence for policy and practice to either complement empirical evidence or, in the absence of research studies, stand alone as the best available evidence. Expert opinion arises out of expertise. Expertise is an important phenomenon amongst health care practitioners and the possession of expertise is highly regarded in all of the health professions.  Essentially linked to the ability of a practitioner to ‘have to hand’ relevant information in a given area of practice, it is generally associated with the possession of large amounts of knowledge and fluency in applying this knowledge. Expertise is difficult to quantify and even more difficult to rank in terms of its reliability. However, a large proportion of health care practice relies on expertise. Practitioners who have expertise are titled experts, and the opinions of experts often represent the best available evidence in areas where research is limited, or where research on a specific question is difficult to conduct.

Adequately addressing the potential role of opinion as legitimate evidence for decision-making requires an exploration of the nature of knowing and of knowledge. Two broad types of knowledge have been identified; propositional knowledge and non-propositional. ²⁶  Propositional knowledge has been described as “...formal, explicit, derived from research and scholarship and concerned with generalizability.”^{26 (page 83)} Non-propositional knowledge is described as “...informal, implicit and derived primarily through practice. It forms part of professional craft knowledge (the tacit knowledge of professionals) and personal knowledge linked to the life experience and cognitive resources that a person brings to the situation to enable them to think and perform.”^{26 (page 83)} It is asserted that evidence-based healthcare requires an integration of both propositional and non-propositional knowledge drawn from evidence bases that have been critically and publicly scrutinized.²⁶

Capturing expert opinion through consensus meetings (eg. the Delphi method) or conferences seeks to reduce bias by replacing individual expert judgments with those of groups of experts who develop an aggregate judgment. However, consensus conferences and other mechanisms for reaching group judgments may also be problematic. It is argued that consensus conferences often take place after the medical community have already settled an issue.²⁷ Considering the collective of experts’ experience is important when published literature is lacking.