pretest probability


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prevalence

Epidemiology
(1) The number of people with a specific condition or attribute at a specified time divided by the total number of people in the population.
(2) The number or proportion of cases, events or conditions in a given population.
 
Statistics
A term defined in the context of a 4-cell diagnostic matrix (2 X 2 table) as the amount of people with a disease, X, relative to a population.

Veterinary medicine
(1) A clinical estimate of the probability that an animal has a given disease, based on current knowledge (e.g., by history of physical exam) before diagnostic testing.
(2) As defined in a population, the probability at a specific point in time that an animal randomly selected from a group will have a particular condition, which is equivalent to the proportion of individuals in the group that have the disease. Group prevalence is calculated by dividing the number of individuals in a group that have a disease by the total number of individuals in the group at risk of the disease. Prevalence is a good measure of the amount of a chronic, low-mortality disease in a population, but is not of the amount of short duration or high-fatality disease. Prevalence is often established by cross-sectional surveys.

pretest probability

An estimate of a patient's likelihood of illness. It is based on or derived from the prevalence of disease in a community.
See also: probability
References in periodicals archive ?
Finally, there is potential for new and more accurate sensors to improve the process further, including using a questionnaire approach such as the Berlin Questionnaire [16], Sleep Apnea Clinical Score [17], or the Elbow Sign Results [18] to identify patients with a high pretest probability of OSA so that level III testing can be skipped entirely and patients can proceed directly to Auto-CPAP management.
Except for the belief that the model may overestimate the pretest probability, this study provided additional possible explanations about hindrances to the application of 2013G.
In patients with a high pretest probability of, or already-documented, CAD, noninvasive anatomical imaging with CTA, or CMR angiography (MRA) may play a secondary role to functional imaging.
Yes Yes No No TABLE II: Causes of Increased D-dimer Athersclerosis Trauma Hepatic disease Disemminated in travasuclar coagulation Infection Pregnancy Inflammation Age of the patient Cancer DVT Thrombolytic therapy PE TABLE III: How best fo use d-dimer assays Clinical Policy from College Emergency Physicians, 2003 Patient Management Recommendation Level A (High Clinical Certainty) No Recommendation specificied Level B (Moderate)-Low Pretest probability Use 1.
(4) Note that Patient 2 has the same post-test probability that was estimated using the positive predictive value (accounting for rounding error), because he was assigned a pretest probability equal to the population prevalence.
This is particularly true with patients whose symptoms and exposure history may suggest a low likelihood of metal toxicity; if the pretest probability of disease is low, the probability that a positive test is a false positive result can become substantial (18).
The most crucial factor governing pretest probability for Lyme disease is exposure history.
In 2013 ESC Guidelines on the management of SCAD (2013G), the indications of CCTA for patients with SCAD should be considered an alternative to stress tests in patients with ejection fraction (EF) >50% and pretest probability between 15% and 50%.
The prevalence of CAD was 78% in high pretest probability group compared to 3% in low pre-test probability group indicating high predictive value of TMT in high pre-test probability group.
However, it clearly demonstrates that such criteria could be used to triage which specimens are more likely to yield meaningful results (ie, increase the pretest probability).
Thus, the advantage of a high negative predictive value in ruling out myocardial infarction (MI) is offset by a high clinical false-positive rate due to non-ACS troponin increases, a balance that is heavily influenced by the pretest probability of ACS in the tested population (7-9).
"That's a very high pretest probability when you're talking about cancer, way higher than when you think about an abnormal mammogram," she said.