How to read a paper Flashcards
Cohort studies
two or more groups of people picked on the basis in differences in their exposure to an agent / procedure
followed up to how many the group develop a disease / complication
case control studies
those with a particular disease and those without are matched, retrospective data collected to look to see if a past exposure potentially caused a disease
cross sectionals survey
a section of a certain population is interviewed to answer a clinical question
hierachy of evidence
Systematic reviews / meta analysis RCT with definitive results RCT without definitive results Cohort studies Case control Cross sectional Case reports
Selection bias
systematic differences in the comparison groups, attributable to inproper randomisation
performance bias
systematic differences in the care provided apart from the intervention being tested
exclusion bias
systematic differences in withdrawals from the trial
detection bias
systematic differences in the outcome assessment
Absolute risk (of death)
The number who died / total number in that group
relative risk of death
AR of intervention / AR of control (y/x)
Relative risk reduction
(ARC-ARI)/ARC
Absolute risk reduction
% who died in control arm - % who died in the intervention arm
number needed to treat
1/ARR
intention to treat analysis
An assessment of the people taking part in a trial, based on the group they were initially (and randomly) allocated to. This is regardless of whether or not they dropped out, fully adhered to the treatment or switched to an alternative treatment. ITT analyses are often used to assess clinical effectiveness because they mirror actual practice, when not everyone adheres to the treatment, and the treatment people have may be changed according to how their condition responds to it. Studies of drug treatments often use a modified ITT analysis, which includes only the people who have taken at least 1 dose of a study drug.
