An evidence based world/cold impartiality?

Ann Winter

Is ebm ‘old hat’?Definition

• “..the conscientious, judicious and explicit use of current best evidence in making decisions about the care of individual patients”

Sackett DL 1996 Evidence –based medicine: what it is and what it isn’t BMJ 312;71-2

• “..argues for the fundamental separability of expertise from expert and of knowledge from knower, and the distillation of medical truth outside the clinical encounter..”

Tannenbaum S 1995 getting there from here: evidentiary quandaries of the US outcomes movement J Eval Clin Practice 1:97-103

• Conventional medicine teaches students to view medicine as a science

• Dr is impartial investigator

• Builds differential diagnoses - facts

• Excludes competing possibilities

• Falsification of hypotheses

Empiricism

• Positivist paradigm

• External reality exists

• Measure

• Experimentation empiricism

• Thus behaviours may be predicted

Positivism

• Empiricism – facts• Determinism – cause and effect• Hypothetico-deductive – testing

hypotheses• Logic – statistical data• Post-positivism – modified positivism

that there cannot be complete objectivity but findings are probably true if validity established

Are there limits to objectivity?

• Karl Popper; science is concerned with the formulation and attempted falsification of hypotheses using reproducible methods that allow generalizable statements about how the universe behaves

http://www.bbc.co.uk/radio4/history/inourtime/inourtime_20070208.shtml

Objectivity

• Clinical agreement - different clinicians show unimpressive levels of agreement beyond chance

• Should acknowledge and measure disagreement• Sackett made no claim to objectivity• Clinical disagreement – clinical judgements are a far cry

from the objective analysis of measurable facts• The facts doctors find when examining patients or their

test results are pre-shaped by what they expect and hope to find

• 50 % accuracy in detecting foot pulsesSackett DL 1991 Clinical epidemiology-a basic science for clinical

measurement Little. Brown & Co. London

What is our positivist evidence ?

Exercise:

Consider what positivist evidence you have used recently and describe it

Where do you go to find evidence?

Interpretation

• Dr’s do not simply assess symptoms and physical signs objectively

• They interpret them by integrating formal diagnostic criteria of the suspected disease (typical textbook patients) with case-specific features of patient with own accumulated case expertise

• Case expertise takes a narrative form – illness scripts of all patients the doctor has seen with similar/contrasting stories

However…!

• anecdotal experience is unrepresentative of the typical case and is a potentially biased influence on decision making

• EB decision making is assessing the current problem in the light of aggregated results of comparable cases in distant populations, expressed as risk and or probability

Squaring the circle

• In physics scientific truths derived from empirical observation about the behaviours of gases fail to hold when applied to single molecules

• Similarly truths about populations from RCT’s cannot be mechanistically applied to individual patients whose behaviour is contextual and idiosyncratic

Misplaced concreteness

• AN Whitehead 1925 Science and the modern world. New York; The Free Press

• Dissonance when trying to apply research evidence to clinical practice

• Tudor Hart (1993) observed that only 10% patients in primary care have the sort of uncomplicated hypertension that lends itself to management by standard evidence based guidelines

• “..Clinical education is preparation for practical, ethical action: what best to do, how to behave, how to discover enough to warrant taking action, which choice to make on behalf of the patient…choices are not governed by hard and fast rules but by competing maxims. that are contextual..”

Maxims

• Concise Oxford Dictionary “..either a general truth drawn from science or experience / a principle or rule of conduct..”

Interpretation

• Hermeneutics – from translation of ancient biblical texts – now expanded to include any detailed analysis of written, spoken, depicted or enacted stories

• The text in the diagnostic encounter is a story about the person as ill:

Person as ill- diagnostic sequence

• Experiential – realisation that he/she is ill• Assigns a medical meaning• John Diamond (1998)..” I told him again the story from

scratch-the aches and pains, the glands, the blood test, the lump. And as I told it in full for the first time, I started to worry. As a medical part-work delivered to my own doctor in instalments it had seemed like no more than a catalogue of vague and differentiated symptoms; as a single story it became something else, something with greater narrative possibilities than a mere swollen gland..”

Because cowards get cancer too. Vermillion Books. London

Person as ill

• Narrative text – what the dr interprets to be ‘the problem

• Medical history

• Perceptual text – dr gleans from physical examination – draws from knowledge learned through practical apprenticeship e.g. hearing heart murmurs

• Instrumental text – diagnostic tests

Riposte to critics

• The practice of ebm means integrating individual clinical expertise with the best available external clinical evidence…by individual; clinical expertise, we mean the proficiency and judgement that individual clinicians acquire through clinical experiences and practice

Phronesis

• Practical reason – phronesis professional mastery & craft of medicine

• Case based narrative ?clinical wisdom is precisely what enables us to contextualise and individualise the problem

Greenhalgh G

Interpretivism

• Alternative to positivism• Social world is actively constructed by human beings

and we are continuously interpreting our social environments

• Roots in philosophy and anthropology• Collection of qualitative approaches• Understand human behaviour in context• Ethnography – groups and communities as a whole• Phenomenology – individuals experiences• Grounded theory – hypotheses and theories emerge

from data

Exercise 2

• Have you used evidence from qualitative research?

• If so what ?

EBP - Definition

• ‘…an opportunistic marriage of convenience between the rationalist iconoclasts of medicine and the policy elite of the NHS R&D initiatives…’

• Rafferty A and Traynor M 1997 Quality and quantity in research policy for nursing

Nursing Times Research 2.1.16-27

• “Evidence-based medicine (EBM) is an approach to health care that promotes the collection, interpretation, and integration of valid, important and applicable patient-reported, clinician-observed, and research-derived evidence. The best available evidence, moderated by patient circumstances and preferences, is applied to improve the quality of clinical judgments”

• McKibbon KA, Wilczynski N, Hayward RS, Walker-Dilks CJ, Haynes RB. The medical literature as a resource for Evidence Based Care, at http://hiru.mcmaster.ca/hiru/medline/mdl-ebc.html

Exercise: How do we rate/consider varying types of research methodology and design?

• Child B scenario