SAR HS 300 Study Guide - Midterm Guide: Colorectal Cancer, Selection Bias, Pap Test
3 Jan 2017
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Sensitivity: the extent to which a test identifies as positive all individuals who have a given disease. a/(a+c) Specificity: the extent to which a test identifies as negative all individuals who are free of a given disease. d/(b+d) Example: 500 elderly individuals are screened for diabetes with a fasting blood glucose. The 265 positive screened then underwent a glucose tolerance test (gtt) and 240 were positive. The 235 who screened negative underwent gtt and 15 tested positive. Calc sensitivity and specificity of screening test: prevalence: 255/500, sensitivity (a/a+c) = 240/255 x 100 = 94. 1. Interpretation: among those tested, 94. 1% of persons with diabetes screened positive by fasting blood glucose screening test. So 5. 9% were false negatives: specificity (d/b+d) = 220 / 245 x 100 = 89. 8. Interpretation: among those tested, 89. 8% of those without diabetes screen negative by fasting blood glucose screening test. Normal range: decided as 2 standard deviations from the mean.
