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L5B - Diagnostic Screening and Testing Define screening including goals…

- - - - Sensitivity
        • measures the proportion of patients with the disease who also test positive
        for the disease in this study. It is the probability that a person with the
        disease will have a positive test result.
      - Sensitivity
        • measures the proportion of patients with the disease who also test positive
        for the disease in this study. It is the probability that a person with the
        disease will have a positive test result.
    - - 1. Was there a clear question for the study to address
        
        *The patients should include patients with a
        high, medium and low probability of having the target disease.*
        
        usefulness of a test is demonstrated in its ability to distinguish between obvious illness and those cases where it is not so obvious
        
        2. Is the Comparison with an appropriate reference standard
        
        The reference (or gold) standard refers to the commonly accepted proof that the target disorder is present or not present.
        
        3. Did all participants get the diagnostic test and the reference standard?
        If not, you will likely have verification bias (missing data)
        • Common when the reference test is harmful or invasive.
        
        4. Could the results of the test of interest have been influenced by the results of the reference standard, or vice versa?
        
        Blind study is best (unable to influence if blinded) – the results both tests should each be decided without knowledge of the results of the other test.
        
        5. Was there a clear description of the disease/condition status of the tested population?
        
        6. Was there sufficient description of the methods for performing the test?
        
        1 more item...
- - - - Likelihood Ratio
        Likelihood Ratois can be used to help adapt the results of a study to a patient, by determining the probability of disease in the patients
        
        LR's
        
        Alternative method of assessing the performance of a diagnostic test
        
        Expres how many times a test result will be found in diseased, compared wth non-diseased people
        
        Indicate the LIKELIHOOD that we can expect a certain result (pos/neg) in a patient with the disorder, compared with the LIKELIHOOD that that result would also be expected from a patient without that disorder
        
        Equations
        
        LR Positive = Sensitivity/(1-specificity)
        
        LR negative = 1 - (sensitivty)/(specificity)
        
        Intrepreting LR's
        
        For a postive test, HIGH LRs indicate that the test is effective at diagnosing disease
        
        For a negative test, LOW LR's indicate that the test is effective at diagnosing non-disease