Diagnostic Test 2×2 (sens / spec / PV / LR)
Sensitivity, specificity, PPV / NPV, accuracy and LR+/- from a 2x2 diagnostic table, with an optional Bayes prevalence adjustment of the predictive values.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- True positives
- 90
- False positives
- 10
- False negatives
- 10
- True negatives
- 90
- Target prevalence
- 5 %
Result: Sensitivity 90%, specificity 90%; LR+ 9; at 5% prevalence PPV 32.1%.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Formulas
- sens = TP/(TP+FN), spec = TN/(TN+FP), PPV = TP/(TP+FP), NPV = TN/(TN+FN), LR+ = sens/(1−spec), LR− = (1−sens)/spec.
- Prevalence
- Sample PPV/NPV reflect the study prevalence; a target prevalence recomputes PPV/NPV by Bayes so the study values are not assumed to transfer.
What you enter
- True positives
- False positives
- False negatives
- True negatives
- Target prevalence (recomputes PPV/NPV)
How this is calculated
Altman DG, Bland JM. Diagnostic tests 1: sensitivity and specificity. BMJ. 1994;308(6943):1552; Diagnostic tests 2: predictive values. BMJ. 1994;309(6947):102. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.