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  • Writer's pictureJoanne Hunt

Factor #5: Limitations of evidence-based medicine

Evidence-based medicine is a much-lauded concept in health services and allegedly draws from three pillars: best available research evidence, clinical expertise, and patient experiencing, values and preferences. Research evidence is arranged into a hierarchy with (generally speaking) systematic reviews at the top, followed closely by randomised controlled trials (RCTs), various other quantitative and mixed methods designs in the middle and qualitative research either not really considered or positioned at the bottom.

The issue with this is that qualitative research is best placed to elucidate patient experiences, and raw patient report (patient testimony) is not considered evidence at all, so patient voice is side-lined from evidence-based medicine despite its alleged ethos. This is a particular concern when patient concerns don’t fit the mainstream healthcare mould, as is the case with medically unexplained symptoms and, currently, Long Covid.

This state of affairs has indubitably facilitated the systematic gaslighting of certain medically contested patient groups, a dynamic which is more pernicious when those patients happen to belong to disadvantaged minority groups. Many RCTs extrapolate their findings to a whole population of patients without considering differences in race, ethnicity, disability, socio-economic status (SES) and so on. Given that samples are often heavily biased towards white, high SES and less severely affected patients (very severely affected patients are typically too ill to participate in research), it is questionable to what extent any findings can be generalised to minority groups within that population. Essentially, the RCT research design risks erasing those who are already marginalised.

One of the reasons for favouring quantitative designs in constructing an evidence base is that quantitative approaches are predicated upon the idea of objective measurement by an objective measurer (researcher) and evidence should of course be objective and value-free. The issue with this is that evidence is neither of these things; rather, evidence is determined by the values and assumptions of those who have the power to determine what classes as evidence, what questions should be asked, which methodologies should be used and what criteria are used to assess the quality of said evidence.

This is something that deserves serious consideration given that science is still quite largely a white, middle-class, able-bodied, male endeavour. Indeed, scratch beneath the surface of this so-called objectivity and you’ll find the history of science is permeated by ethnocentric (white-centric), androcentric, ableist, cis-normative and heteronormative assumptions. Such assumptions mean that any evidence-base, and the healthcare that derives from it, may not apply to or accommodate people who don’t fit a particular sociodemographic profile. This raises particular concerns for people with Long Covid who are already marginalised, who essentially do not fit what I call the mainstream mould.

Interestingly, the NIHR report on Long Covid draws quite heavily on patient voice (qualitative data), in part because a quantitative evidence base is lacking and in part indubitably because of the pressure exerted by a collective and cohesive Long Covid patient voice. The report also recognises that research rarely gives voice to marginalised groups. Greater emphasis on patient voice is to be welcomed, particularly when that voice is a marginalised one, but it should be noted that this is an approach that has arisen out of necessity, not out of insight, and it raises serious questions about how other patient groups have been researched and treated in the past. At some point, these questions must be addressed.

There are other issues with evidence-based practice related to the above, when particularly powerful groups begin to construct evidence bases even when much of the scientific community repeatedly critique such evidence as theoretically and methodically flawed. This dynamic, known within a healthcare context as eminence-based medicine, is a particular issue within the field of ME/CFS and other illnesses that are framed within the NHS as ‘medically unexplained symptoms’; this will be discussed in a later blogpost.

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