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You are studying a new rapid flu test’s performance in your ED. Using PCR as a gold standard, you studied 100 kids at the peak of flu season, of whom 60 had influenza and 40 did not. Of the 60 who had influenza by PCR, 54 had a positive rapid flu test, and of the 40 who did not have influenza by PCR, 2 had a positive rapid flu test.
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November 27, 2018 at 12:12 pm
C) Sensitivity = 54/60, Specificity = 38/40
Disease (PCR) + Disease (PCR) –
Rapid flu + 54 2
Rapid flu – 6 38
Sensitivity is positivity in disease, or 54 positive rapid flu tests in 60 diseased patients. Specificity is negativity in health, or 38 negative rapid flu tests in 40 healthy patients.
The positive predictive value of the test (PPV) is how many patients with a positive test have diseased = 54/56. The negative predictive value (NPV) is how many patients with a negative test are healthy = 38/44.