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Does odds ratio depend on prevalence?
Unfortunately, there is a recognised problem that odds ratios do not approximate well to the relative risk when the initial risk (that is, the prevalence of the outcome of interest) is high. For example: “The odds ratio is approximately the same as the relative risk if the outcome of interest is rare.
Is odds ratio an outcome measure?
Odds Ratio (OR) is a measure of association between exposure and an outcome. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure. Important points about Odds ratio: In rare outcomes OR = RR (RR = Relative Risk).
How do you interpret prevalence risk ratio?
For example, if 80 out of 100 exposed subjects have a particular disease and 50 out of 100 non-exposed subjects have the disease, then the odds ratio (OR) is (80/20)/(50/50) = 4. However, the prevalence ratio (PR) is (80/100)/(50/100) = 1.6.
What is the difference between odds ratio and prevalence ratio?
In cross-sectional studies, the odds ratio is also referred to as the prevalence odds ratio (POR) when prevalent cases are included, and, instead of the RR, the prevalence ratio (PR) is calculated. Similarly, PR as such neither equals the RR nor the incidence (density) rate ratio.
What is prevalence risk?
In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time.
Is prevalence a measure of risk?
While the prevalence represents the existing cases of a disease, the incidence reflects the number of new cases of disease within a certain period and can be expressed as a risk or an incidence rate.
Is the prevalence odds ratio the same as the risk ratio?
The Prevalence Odds Ratio is not an approximate measure of the Risk Ratio – it is a paremter on its own that can be used in cross-sectional studies as a measure of the association between exposure/factors and the outcome of interest, without any need to mention Risk ratio.
How is the odds ratio used in economics?
The odds ratio can also be used to determine whether a particular exposure is a risk factor for a particular outcome, and to compare the magnitude of various risk factors for that outcome. OR=1 Exposure does not affect odds of outcome. OR>1 Exposure associated with higher odds of outcome. OR<1 Exposure associated with lower odds of outcome.
Is there a difference between risk and odds?
Nonetheless, interpretation of OR is difficult since confusing between risk and odds can lead to incorrect quantitative interpretation of data such as “the risk is X times greater,” commonly reported in studies that use OR.
How to calculate the risk ratio of a disease?
To calculate the risk ratio, first calculate the risk or attack rate for each group. Here are the formulas: Attack Rate (Risk) Attack rate for exposed = a ⁄ a+b Attack rate for unexposed = c ⁄ c+d. For this example: Risk of tuberculosis among East wing residents = 28 ⁄ 157 = 0.178 = 17.8%