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Hierarchy of Evidence
1
- single blind
- double blind
- triple blind
- open study
Hiearchy
of Evidence
Endpoint/ Primary Outcome
Variable used to judge the effectiveness of an intervention (ex. response rate).
"Hard endpoint": explicit outcome variable that is not vulnerable to serious errors in measurement or interpretation.
By: Claudia Medina 18-8032
What is Evidence Based Learning?
"Valid evidence of clinical benefit and costeffectiveness
is what will influence purchasers of health care."
There are 2 forms of evidence:
- Primary
- Secondary
Jones, Claire. “Evidence-Based Medicine (1) Research Methods.” Pharmaceutical Journal, 22 Sept. 2009, www.pharmaceutical-journal.com/learning/learning-article/evidence-based-medicine-1-research-methods/10979165.article.
Case Reports & Case Series
Case report: describes the medical history of a single patient
Case series: collection of similar reports
There are no controls so they are statically invalid, only supportive.
Thank you!
Randomized Controlled Trials
(Double blind trials)
Research study typically used to assess the relative effects of drugs.
Patients are randomly allocated to one intervention or another, one being a control group.
There are different types of groups & blinding used depending on the study, sample size or resources:
- parallel
- matching/pairing
- cross-over
- factorial
Cohort Studies
Observational studies of subjects with a specific disease or characteristic.
This can be compared with a control group.
Complications: time, outside influences/variables
Case Control Studies
Concerned with what causes a disease.
The diseased are paired with controls and the data is based on past exposure to the causative agents.
This research produces fast results but isn't as reliable.
Statistics
P-value: result of the statistical test used to assess the probabilty that the results of the trial is a real effect & did not occur by chance.
- <0.5 is indicative of a true difference
95 % confidence interval: represents the range values within the true population value lies.
Intention to treat analysis: the results used include all the orginal patients, including those who have dropped out.
Expressing Results
Absolute risk reduction (ARR): the amount by which drug X reduces the risk of death
Relative risk reduction (RRR): the amount by which the risk (of death) is reduced by drug X as a comparative percentage of the control
Number needed to treat (NNT): the number of people who need to be treated to produce one additional successful outcome
- Ex. How many patients NNT by drug X instead of placebo to prevent one death in 5 yrs?
Odds ratio: the ratio of patients in the treatment group succumbing to a particular end point of the trial to the number who don't, compared to the patients in the control group
- The odds of dying compared with the odds of surviving for patients in the intervention group treated with drug X are 358/1,642= 0.22, and for patients in the control group
501/1,497 = 0.33. The OR will therefore be 0.22/0.33 = 0.67.
Cross Sectional Surveys
Measure of the frequency of a disease or risk in a defined population
Systematic Reviews or Meta-analyses
Medical literaure reviews, usually involving an expert, and making a conclusion about a specific disease or condition.
Systematic review:
- Can be subjected to bias from reviewer's personal opinions.
- All trials pertaining that specific problem would be reviewed and compiled to discuss the findings as a whole.
Meta-analysis:
- Specific statistical strategy for deriving a numberical estimate from the results of compiled RCTs.