Statistics and Evidence Flashcards
Why is decision making important in medicine? (3)
- doctors make decisions very often
- these decisions have effects in patients, their families and wider society
- understanding the medical decision making process and the role if evidence can improve medical practice
what is the hypothetico-deductive model of decision making?
coming up with a hypothesis, and trying to find evidence to prove/disprove
name 4 factors influencing an evidence based decision
- evidence from research
- clinical expertise
- available resources
- patient preferences
name 3 reasons why we need EBDM
- limited time to read
- inadequacy of traditional sources of infromation
- disparity between diagnostic skills/clinical judgement and up-to-date knowledge/clinical performance
Name 5 ways in which evidence based decision making is possible
- development of strategies for effectively identifying and appraising evidence
- creation of systematic reviews and summaries
- creating of evidence based journals and clinical guidelines
- creation of information systems
- identification and application of strategies for lifelong learning
What types of research question are the following study designs suitable for:
- cohort studies
- case controls
- RTCs
- qualitative approaches
- Diagnostic and screening studies
- Systematic reviews
- prognosis; cause
- cause
- treatment interventions. Benefits and harm
- patient perspective
- identification
- summary of evidence for a specific question
- what are background questions?
2. what are foreground questions?
- questions querying general knowledge of disorder (e.g who what where when)
- questions querying specific knowledge about managing patients with disorder (PICO)
What does PICO stand for?
P - population
I - intervention
C - comparator
O - outcome
What is a diagnostic test
any kind of medical test performed to aid the diagnosis or detection of disease
Define:
- Sensitivity
2. Specificity
- the ability of a test to correctly identify all those with disease
- the ability of a test to correctly exclude all those without disease
How do you calculate:
- Sensitivity
- Specificity
- no of true positives ÷ all those with disease
2. number of true negatives ÷ all those without disease
Define:
- Positive Predictive Value
2. Negative Predictive Value
- the chance of having disease with a positive test result
2. the chance of not having disease with a negative test result
How do you calculate:
- Positive predictive value
- negative predictive value
- number of true positive ÷ number who test positive
2. number of true negatives ÷ number who test negative
- Which aspects of test performance are affected by prevalence?
- How do they change as prevalence increases
- predictive values
2. PPV rises and NPV falls
What are likelihood ratios?
how the belief about the chance of disease has changed as a result of the test
What is screening?
the systematic application of a test, to identify individuals at sufficient risk of a specific disorder to warrant further investigation or direct preventative action, amongst people who have not sought medical attention on account of symptoms
What type of prevention is screening thought as?
secondary prevention
What are the criteria for the condition being screened for? (3)
- must be an important health problem
- epidemiology and natural history must be adequately understood
- Cost effective primary prevention must have been implemented
What are the criteria of the screening test (4)
- should be a simple, safe, precise and validated screening test
- a suitable cut off for the test value should be agreed
- test should be acceptable
- There should be an agreed policy on further management
What are the criteria for the TREATMENT of the condition being identified by screening? (3)
- there should be an effective treatment, with evidence of early treatment leading to better outcomes
- there should be agreed policies covering who should be offered treatment
- clinical management of the condition should be optimised prior to the implementation of a screening programme
What are the criteria for the screening programme? (5)
- there must be RCT evidence that the programme is effective in reducing morbidity and mortality
- there should be evidence that the whole programme is acceptable to professionals and the public
- benefit should outweigh the harm
- opportunity cost should be economically balanced
- there should be a plan for quality assurance
- Why is selection bias a particular problem with assessing screening programmes
- What is sojourn time?
- What is length bias?
- What is lead time bias?
- the people who will opt in to screening programmes are often very health aware and therefore likely to have good outcomes
- the length of time of disease before it causes morbidity/mortality
- screening is disproportionately likely to detect linger progressing disease, which tend to have better outcomes (making the screening programme look better)
- screening makes disease life longer because it is found earlier.
Which study designs are useful for investigating the following areas:
- diagnosis
- aetiology
- prognosis
- treatment
- patient views
- cross sectional study
- cohort study
case control - cohort study
- RCT
- qualitative research
Name 6 benefits of systematic reviews
- contain all the available evidence to answer a question
- includes unpublished research or that published in non-english language journals
- increase the total sample size, and so increase levels of certainty and precision
- indicate heterogenicity (variation) among studies
- permit subgroup analyses
- permit sensitivity analyses