Research methods and evidence Flashcards
Aetiology
The study of the causes.
Prognosis
a forecasting of the probable course and outcome of a disease, esp. of the chances of recovery.
screening
a test or examination to discover if there is anything wrong with someone:
how does EBM bridge the gap between research and clinicians
Evidence is reviewed by experts.
Often, this results in Guidelines for treatment, and recommendations for future research.
UK example: National Institute for Health and Clinical Excellence- NICE.
Clinicians’ are expected to implement recommendation.
Some practical problems often arise…
outline the NICE guidelines for mental health and behavioural conditinos
23 complete guidelines
Example: three sets of guidelines for depression:
Adults
Children and young people
Depression with a chronic physical health problem
what does EBM stand for?
evidenced based medicine
what are the aims of EBM
Aim: aims to apply the best available evidence gained from the scientific method to medical decision making. How? By ranking evidence based on: the quality of studies The strength of their findings
what does the , U.S. Preventive Services Task Force use to test if intervention is effective?
Level I: Evidence obtained from at least one properly designed randomized controlled trial.
Level II-1: Evidence obtained from well-designed controlled trials without randomization.
Level II-2: Evidence obtained from well-designed cohort or case-control analytic studies, preferably from more than one centre or research group.
Level II-3: Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled trials might also be regarded as this type of evidence.
Level III: Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees.
what is the process of an EBM review?
Search
Read, include & exclude studies.
Appraise, according to set criteria to establish quality.
Synthesise where possible, by pooling results across studies.
what is EBM research based in?
Appraisal
Of published papers
Depends in quality of search
And on good critical criteria
Laboratory tests
Clinical experience
what are the main issues highlighted by EBM research
Main issue:
Systematic and
Critical
what is the critical apprraisal of method?
Critical Appraisal of Method:
Example of an item: Participants
Who is the study about?
Recruitment
Is it representative? (APD in prisons)
Are inclusion criteria well defined?
GP case notes for the tag ‘depression’, rather than diagnostic criteria
Exclusion
Have groups been included that could unduly sway the results? Women’s’ anxiety levels, not excluding pregnant.
outline a way to assess treatments
Randomised control trials
The gold standard
Randomisation:
- Controls for unknown bias and confounding
Blinding: single and double
Control group
why are randomised control trials often flawed?
Incomplete randomisation (drop-out, allocation bias)
Length of trial? (e.g. dynamic versus behaviour therapy)
Blinding patients?
Assessor?
Choice of control group? (Are waiting lists ethical?)
Choice of outcome? (Days off work might be a primary outcome to government, but not to patients…)
How can RCT be probalamatic?
Clearly successful intervention (implemented already or reviewed in meta-analysis
): replace with head to head or non-inferiority trials.
Unethical (AZT)
antiviral drug- treatment for aids
Very large subject groups needed, or when cases are very rare (Examining the effect of counselling on ‘unifying’ personality in people with split personality)
Arguably, when treatment cannot be standardised (think which psychological model would fare better for standardisation)
outline observational methods as an EBM technique
Other forms of evidence: Observational methods: prospective cohorts Cohort studies (Example):
Hill & Dolls’ famous ‘Doctors Study’ started in 1951, finished in 2001, and provided strong evidence the smoking was closely linked to lung cancer.
Outline prospective cohorts
Longitudinal. Baseline measures. No intervention, observe follow up over time, measure outcome. Inform about causality. Often large, costly, and time consuming.
give an example of a systematic review of a perspective cohort
Examination of GP consultations with patients with uncertain causes/ treatments
Split GP behaviours into affective and cognitive reassurance
Examines patients outcomes at follow up
Pincus T, et al., Cognitive and affective reassurance and patient outcomes in primary care: a
systematic review. Pain. 2013 Nov;154(11):2407-16.
outline case-control studies
Retrospective.
Select ‘cases’ and match with control group. ‘caseness’ is the outcome.
Measure exposure in the past to suspected factor.
If Odds are significantly higher in cases, exposure factor may have contributed to developing disorder.
Outline an example of a case-control study
Sudden Infant Death Syndrome (SIDS) Sudden, unexpected, unexplained Rare: less than 1 in 1000. How to investigate?... Evidence now supports brain abnormalities (in some), viral infection (in some), position face down (in some…)
Outline retrospective cohort
Schizophrenia and flu in second trimester
First identified from cohort correlation: flu epidemic curve and later incidence increase.
How to study
Brown et al. (2004) were able to analyse blood serum from expecting mothers (59 children with Schizophrenia,105 matched controls)
what are cross-sectional/ correlations
A snapshot in time: all variables measured simultaneously.
Statistic tests inform on the relationship between two variables: significance and grade of relationship (high, moderate, low).
Outline the Bradford Hill criteria
Time line Plausibility of model Research data from different designs/ samples Quality of relationship (R, d’, p) Dose-response Reversibility
what are the problems for EBM?
Measurements: surrogate (e.g. behaviour for cognition), self-report, validity (stress?), reliability, cut-points Can’t blind Often ignore / can’t measure main issue (communication) Multi-faceted problems
outline the issues with experiments
Can’t always generalise from animals (Seligman et al, 1978)
Can learn about internal processes (e.g. Stroop in Spider Phobics)
High on reliability but what about validity?
what is the issues with publication bias
Replication (not original)
Refutation (Type II error)
Political (from experimenters or editors)
Outline the issues with case reports
Individual patients (e.g. Freud)
Form of a story
Can form a case series
Evidence? Controversial
AIDS was identified through case reports
Outline the procs and cons of case studies
Necessary for rare disorders: split personality or neuropsychology
But no control for bias or confounding
Empirical quality can be improved in single subject designs (experimental, base-line, manipulation, outcome)
Outline the hierarchy of case evidence
Systematic reviews and meta-analysis Randomised Control Trials Cohort studies Case-control studies Cross-sectional studies Case reports
outline the strengths of evidence based psycholgoy
strong evidnece in
Experiments
Genetic research
BUT most interventions are based on case-studies / experience:
Treatment is never the same for two individuals
Most therapists ‘eclectic’
why is EBM not popular?
Challenges clinical experience / authority
Forces clinicians to continue learning
Disputes value of clinical decisions based on:
anecdotes,
press cutting,
expert opinion
