Tag: Positive Likelihood Ratio

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How To Select A Diagnostic Test?

A diagnostic test is a clinical procedure used to determine the presence, absence, or extent of a disease or condition. These tests are essential for diagnosing illnesses, guiding treatment decisions, and monitoring disease progression. They can involve various methods, such as physical examinations (e.g., manual tests such as valgus test of the knee, apprehension test of the shoulder), imaging (e.g., X-rays, MRIs), or laboratory tests … Continue reading How To Select A Diagnostic Test?

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Diagnostic Skills

Post-test Probability

Post-test probability: is the probability of the presence of a disease after a confirmatory diagnostic test. Method I:  Let us estimate post-test probability by hand calculation using the data from the study by Capra et al (1). To do this, we need to know the pre-test probability and the positive likelihood ratio values. For this purpose, let us assume the pre-test probability as 0.55. And, we will … Continue reading Post-test Probability

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Diagnostic Skills

Likelihood Ratios

Let us continue using the data from the study by Capra et al (1). The likelihood ratio is the percentage of diseased individuals with a given test result divided by the percentage of healthy individuals with the same test result (2). The likelihood ratios (positive and negative) can be calculated by using the following formulae (2): + LR = sensitivity / (1- specificity) = True positive rate / … Continue reading Likelihood Ratios

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