odds ratio (OR)

(Related concepts: absolute risk reduction, number needed to treat and relative risk) The ratio (quotient) of the exposure odds among the cases (subjects who are ill or have died, for example) to that among the controls (subjects who are not ill or who are alive, for example). Note: The odds ratio is the estimate of relative risk used in a type of study (case-control) in which it is impossible to calculate relative risk directly. It is a good estimate of relative risk in cases in which the disease is rare. Thus, if the results of a trial are that the probability of death is 25% in the control group and 10% in the experimental group, the odds ratio of survival is [0.10 ÷ (1.0 — 0.10)] ÷ [(0.25 ÷ (1.0 — 0.25)] = 0.33.

and • provides information on costs and financial impact. Note 2: The report may optionally discuss organisational considerations. Note 3: A “mini-HTA” may be as rigorous as an HTA report but typically has a restricted scope and so is quicker to produce. Note 4: Related terms include health technology, HTA report, rapid review, level of evidence