Calculates sensitivity, specificity, predictive values, and other indices from a 2x2 table.
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Calculation basis and official references
Reviewed on:
This calculator is not a diagnosis, treatment plan, or prescription. Please consult a qualified clinician about your medical decisions.
Formula basis
Sensitivity = a/(a+c), specificity = d/(b+d), false negative rate = c/(a+c), false positive rate = b/(b+d), positive predictive value = a/(a+b), negative predictive value = d/(c+d), prevalence = (a+c)/(a+b+c+d). When a+c, b+d, a+b, c+d, or the overall total equals 0, the corresponding index is mathematically undefined and this calculator does not produce a result.
Calculation method
Organizes test results (positive/negative) and actual disease status into a 2x2 table (true positive a, false positive b, false negative c, true negative d) and calculates sensitivity, specificity, predictive values, and prevalence.
Exclusions and checks required
When a+c, b+d, a+b, c+d, or the overall total equals 0, the relevant index is mathematically undefined, so this calculator stops and does not compute a result.
Positive and negative predictive values depend on the prevalence of the studied population (a+c versus b+d), so the same test can yield different predictive values in different populations. Sensitivity and specificity, by contrast, are properties of the test itself.
These are statistical indices derived from a 2x2 table; interpreting an individual test result clinically requires expert judgment that accounts for the test's characteristics and the patient's background.
Sensitivity, specificity, and related figures describe the statistical performance of a test method; they do not by themselves confirm whether any individual test result is correct.
Who is this calculator for? Test Accuracy (Sensitivity/Specificity)
Calculates sensitivity, specificity, predictive values, and other indices from a 2x2 table.
What values should I enter?
Applies to: Lab values
How should I interpret this estimate?
Organizes test results (positive/negative) and actual disease status into a 2x2 table (true positive a, false positive b, false negative c, true negative d) and calculates sensitivity, specificity, predictive values, and prevalence.
How to use
Enter your input values and press Calculate.
Review the result and compare it with expected context.
Sensitivity = a/(a+c), specificity = d/(b+d), false negative rate = c/(a+c), false positive rate = b/(b+d), positive predictive value = a/(a+b), negative predictive value = d/(c+d), prevalence = (a+c)/(a+b+c+d). When a+c, b+d, a+b, c+d, or the overall total equals 0, the corresponding index is mathematically undefined and this calculator does not produce a result.