lecture 19

# lecture 19 - Goals Lecture 19 Calculate interpret and...

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1 Lecture 19 Screening Goals Calculate, interpret, and identify the relationships between: Specificity Sensitivity Positive Predictive Value (PPV) Negative Predictive Value (NPV) Efficiency Describe and give examples of conditions for establishing screening program Describe and give examples of biases in screening Screening Programs { Purpose is to recognize disease in asymptomatic people { Screening is not diagnosis! { Early detection leads to changes in disease trends and control Characteristics of a Good Screening Test { Simple { Quick { Inexpensive { Safe { Acceptable { Valid and reliable Establishing Screening Programs { The condition is an important health problem { Early detection improves survival { There is a suitable test for detecting early disease (reliability and validity) { The screening tool is acceptable { Finding cases is cost-effective in relation to cost of treatment and care { There are facilities for diagnosis and treatment { There is an acceptable treatment for the disease { Screening is a continuous process { Yield = amount of previously unrecognized disease that is identified { Increased by: z Screening high risk populations z Screening more than once

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2 { Ability of a test to give consistent results { Affected by variability of test chemicals or methods used { Use standard lab tests { Run multiple samples { Affected by variability in people taking the measurements { Train the observers { Use more than one observer and have them double-check the others’ work { Validity = ability to predict who has disease and who does not have disease Sensitivity – the ability to correctly identify those with disease High sensitivity = few false negatives Specificity – the ability to correctly identify those without disease High specificity = few false positives Measures of Validity { Ideal screening test is 100%
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lecture 19 - Goals Lecture 19 Calculate interpret and...

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