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How to Calculate Sensitivity of Screening

Screening tests such as Pap smears, mammograms and urinalysis are designed to assess patients who are of need of further evaluation for a specific disease. Screening tests help identify patients early in the disease cycle before the patient develops symptoms and should, therefore, improve prognosis.

  1. Definition

    • The test's sensitivity is the ability of the screening test to accurately determine patients who have the disease. A test that is 90 percent sensitive means, for example, for every 10 patients with the disease, nine are accurately diagnosed, and one patient is given a false-negative result.

    Calculation

    • To calculate the sensitivity of the test, patients with the disease detected by the screening test are divided by the total number of patients with the disease. Multiply by 100 to get the percentage.

    Acceptable Sensitivity

    • There is no consensus on an acceptable sensitivity level. It depends on how widespread the disease is in the population being screened, alternative screening methods, cost of the test, invasiveness of the test, treatment and benefit of the test.

    Other Calculations

    • The sensitivity of the test goes hand in hand with the specificity of the test. The higher the sensitivity and specificity of the test, the more precise the screening method. The predictive value of the test is determined by the specificity and sensitivity of the test and the prevalence of the disease in the screened population.

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