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Diagnostic 2×2 — Sens, Spec, Youden

§6.1
Rev 4.6 · reviewed Feb 2026
Diagnostic 2×2
Evaluates a test against a reference standard. Enter counts by test result and true disease status.
Source formula: Youden WJ. Cancer 1950;3:32–5.
Table. Test result by disease status
Disease +Disease −Total
Test +60
Test −240
Total50250300
* All CIs are Wilson score intervals. Wilson EB. J Am Stat Assoc 1927;22:209–12.
† Youden's J = sensitivity + specificity − 1. Youden WJ. Cancer 1950;3:32–5.
Sensitivity (95% CI)*
90.0% (78.6%–95.7%)
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Specificity (95% CI)*
94.0% (90.3%–96.3%)
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PPV (95% CI)*
75.0% (62.8%–84.2%)
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prevalence-dependent
NPV (95% CI)*
97.9% (95.2%–99.1%)
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prevalence-dependent
Youden's J†
0.840
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LR+ / LR−
15.0 / 0.11
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Test performance
90% / 94%
Sensitivity 90%, specificity 94% (Youden's J 0.84). A positive result multiplies the odds of disease about 15-fold. PPV/NPV shift with prevalence.
The test catches 90% of true cases and correctly clears 94% of non-cases. Remember that PPV and NPV shift with prevalence — a test that looks strong in a high-prevalence clinic can mislead in screening. A positive result multiplies the odds of disease about 15-fold.
Understand what this is measuring