NNT & Absolute Risk Flashcards
What is numbers needed to treat (NNT)?
A measure that indicates how many patients would require an intervention to reduce the number of expected outcomes by 1.
E.g. NNT of 20 means would need to treat 20 patients to prevent 1 event.
How is NNT calculated?
1/absolute risk reduction
Then rounded to the next highest whole number
What is the social selection/mobility theory?
That ill health can limit social mobility due to a decreased ability to work, and decreased income, leading to a lower social class.
What is the artefact theory?
Proposes that the observed differences are due to differences in measurement (so not actually present)
What is the idealist theory?
Suggests that individuals’ construction of health is different in different groups, so they might define health differently
What is the cultural/behavioural health theory?
Proposes that differences in behaviour cause differences in health.
What is the materialist health theory?
emphasises the role of economic and social factors, such as income, education, and employment, in shaping health outcomes.
What is relative risk?
The ratio of risk in the experimental group to risk in the control group.
EER = rate at which events occur in the experimental group
CER = rate at which events occur in the control group
E.g. If we look at a trial comparing the use of paracetamol for dysmenorrhoea compared to placebo:
- Total number of patients receiving paracetamol = 100,
Of those 100, 60 experienced pain relief - Total number of patients receiving placebo = 80
Of those, 20 experienced pain relief
EER = 60/100 = 0.6
CER = 20/80 = 0.25
Relative risk ratio = EER / CER = 0.6/0.25 = 2.4
What does a relative risk >1 mean?
Then the rate of an event is increased compared to controls.
It is therefore appropriate to calculate the relative risk increase if necessary (see below).
