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Diagnostic test (2×2 table)

Assesses diagnostic performance against a reference standard using true/false positive and negative study counts.

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Check the population, units and version. The result shows the formula or classification; it does not make an automatic treatment decision.

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Method · Limits of application

2×2:sensitivity/specificity/PPV/NPV; Wilson 95% proportions; Simel 1991 logarithmic LR intervals; not Wald proportions

The table requires binary classification of the test and reference status, with consistent counts for the same population. Positive and negative predictive values depend on prevalence and do not transfer automatically to another population. A zero denominator may make a measure undefined. Wilson intervals for proportions and logarithmic intervals for likelihood ratios are different methods; zero counts and small samples require specific interpretation. This analysis alone does not establish the quality of the reference standard or validate the test.

Conditions of use

Check the population, units, inclusion and exclusion criteria, and version in the original source. A result alone does not establish a diagnosis, discharge decision or prescription.

Documented parameters

True positives (TP): positive test and disease present
False positives (FP): positive test and no disease
False negatives (FN): negative test and disease present
True negatives (TN): negative test and no disease

3/3 reference cases checked. Numerical tests are not clinical validation.

Sources and documentation

Documented formula

Transcribed from the source or a recorded revision; this is not a clinical recommendation.

Sensitivity = TP / (TP + FN) · Specificity = TN / (TN + FP) · PPV = TP / (TP + FP) · NPV = TN / (TN + FN) · Accuracy = (TP + TN) / total.

LR+ = Sensitivity / (1 − Specificity) · LR− = (1 − Sensitivity) / Specificity.

95% confidence intervals: Wilson score for proportions; logarithmic method for likelihood ratios (Simel 1991), SE(ln LR+) = √(1/TP − 1/(TP+FN) + 1/FP − 1/(FP+TN)).

References

Identifier: teste-diagnostico-2x2

Original clinical content: Brazilian Portuguese.

Method version

2×2:sensitivity/specificity/PPV/NPV; Wilson 95% proportions; Simel 1991 logarithmic LR intervals; not Wald proportions

teste-diagnostico-2x2@native-2026-10-03+badc4e7b62c9

Source for the active edition

The bibliographic edition identifies the source. By itself, it proves neither full conformity of the formula nor clinical approval.

Synthetic cases checked (3)

Synthetic cases for checking the implementation, with no patient data.

Case 1

reference-001

Inputs

True positives (TP): positive test and disease present: 231
False positives (FP): positive test and no disease: 32
False negatives (FN): negative test and disease present: 27
True negatives (TN): negative test and no disease: 54

{
  "vp": 231,
  "fp": 32,
  "fn": 27,
  "vn": 54
}

Expected result

{
  "se": 89.53,
  "sp": 62.79,
  "vpp": 87.83,
  "vpn": 66.67,
  "lrp": 2.406,
  "lrn": 0.1667,
  "acc": 82.85
}

Actual result

{
  "se": 89.53488372093024,
  "sp": 62.7906976744186,
  "vpp": 87.83269961977186,
  "vpn": 66.66666666666666,
  "lrp": 2.40625,
  "lrn": 0.1666666666666666,
  "acc": 82.84883720930233,
  "seLo": 85.20214058440061,
  "seHi": 92.70759948181326
}

Case 2

reference-002

Inputs

True positives (TP): positive test and disease present: 8
False positives (FP): positive test and no disease: 1
False negatives (FN): negative test and disease present: 2
True negatives (TN): negative test and no disease: 9

{
  "vp": 8,
  "fp": 1,
  "fn": 2,
  "vn": 9
}

Expected result

{
  "se": 80,
  "sp": 90,
  "lrp": 8,
  "lrn": 0.2222,
  "seLo": 49.02,
  "seHi": 94.33
}

Actual result

{
  "se": 80,
  "sp": 90,
  "vpp": 88.88888888888889,
  "vpn": 81.81818181818183,
  "lrp": 8.000000000000002,
  "lrn": 0.22222222222222215,
  "acc": 85,
  "seLo": 49.016246912213234,
  "seHi": 94.3317849062233
}

Case 3

reference-003

Inputs

True positives (TP): positive test and disease present: 0
False positives (FP): positive test and no disease: 5
False negatives (FN): negative test and disease present: 0
True negatives (TN): negative test and no disease: 20

{
  "vp": 0,
  "fp": 5,
  "fn": 0,
  "vn": 20
}

Expected result

{
  "error": true
}

Code and reproducibility

This tool’s code on GitHub

Download code and tests

Sources, version and reproduction instructions

The code tests are technical checks. Clinical approval and professional translation review are recorded separately.

Relationship with cancer research

Support for research — context required

Diagnostic performance measures from study data. They may support the evaluation of cancer tests if the reference standard and sample are appropriate.

Applications: Early detection and risk assessment · Clinical trials and methods

Treatment resistance

A study of 96 patients with epithelial ovarian cancer evaluated the sensitivity and specificity of biomarkers for platinum resistance, defined by the progression-free interval (Gerber et al., 2023). This table supports analysis at a fixed threshold using user-supplied TP/FP/FN/TN counts; it does not measure gelsolin, select a threshold, generate ROC/AUC, or reproduce the study from rounded percentages.

DOI: 10.1186/s13048-022-01086-x