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Sensitivity and Specificity

Sensitivity and Specificity. Bioterrorism Epidemiology Module 10 Missouri Department of Health And Senior Services. Precision (Reliability). Measure of a random variation around a specific value Variation in method Variation in observer Intra- and inter observer

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Sensitivity and Specificity

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  1. Sensitivity and Specificity Bioterrorism Epidemiology Module 10 Missouri Department of Health And Senior Services

  2. Precision (Reliability) • Measure of a random variation around a specific value • Variation in method • Variation in observer • Intra- and inter observer • Epidemiology assumes that background fluctuations in disease rates are random • Increasing study size can usually increase precision

  3. Sensitivity and Specificity Sensitivity persons with the disease detected by surveillance system total number of persons with the disease X 100 Specificity persons without the disease who are negative in the surveillance system total number of persons without the disease X 100

  4. Sensitivity Respiratory Disease + - 350 1900 + - Test Results 150 7600 persons with the disease detected by surveillance system total number of persons tested with the disease X 100

  5. Sensitivity Respiratory Disease + - 2250 350 1900 + - Test Results 150 7750 7600 500 9500 Sensitivity = 350 / 500 * 100 = 70%

  6. Specificity Respiratory Disease + - 350 1900 + - Test Results 150 7600 persons without the disease who are negative in the surveillance system total number of persons without the disease X 100

  7. Specificity Respiratory Disease + - 350 1900 2250 + - Test Results 150 7600 7750 500 9500 Specificity = 7600 / 9500 * 100 = 80%

  8. Positive and Negative Predictive Values Positive Predictive Value = True Positives/All Positives Negative Predictive Value = True Negatives/All Negatives

  9. Positive Predictive Value Respiratory Disease + - 350 1900 + - Test Results 150 7600 Positive Predictive Value = True Positives/All Positives

  10. Positive Predictive Value Respiratory Disease + - 350 1900 2250 + - Test Results 150 7600 7750 500 9500 Positive PV = 350 / 2250 * 100 = 16%

  11. Negative Predictive Value Respiratory Disease + - 350 1900 + - Test Results 150 7600 Negative Predictive Value = True Negatives/All Negatives

  12. Negative Predictive Value Respiratory Disease + - 350 1900 2250 + - Test Results 150 7600 7750 500 9500 Negative PV = 7600 / 7750 * 100 = 98%

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