EXPLORACION BASADA EN LA EVIDENCIA

LR + (LIKELIHOOD RATIO DEL VALOR POSITIVO)

PRUEBA A VALORAR PRUEBA DE ORO

ENFERMOS SANOS

POSITIVO Verdaderos Positivos

Falsos Positivos

NEGATIVO Falsos Negativos Verdaderos Negativos

LR + = [VP/ (VP + FN)] / [FP/ (FP+VN)]

LR + = SENSIBILIDAD / (1- ESPECIFICIDAD)

LR - = LIKELIHOOD NEGATIVO

PRUEBA A VALORAR PRUEBA DE ORO

ENFERMOS SANOS

POSITIVO Verdaderos Positivos

Falsos Positivos

NEGATIVO Falsos Negativos Verdaderos Negativos

LR - = [FN / (VP + FN)] / [ VN / (FP + VN)]

LR - = ( 1 – SENSIBILIDAD) / ESPECIFICIDAD

increasing impactIncreasing impact

LR: Impact on Likelihood of Disease

LR = 1

No

Impact on Likelihood of

Disease

0

LR = 0.3

Less

Likely

LR = 0.2

Less

Likely

LR = 0.1

Less

Likely

LR = 0.01

Less

Likely LR = 3

More

Likely

LR = 5

More

Likely

LR = 10

More

Likely

LR = 100

More

Likely

Does This Adult Patient Have

Acute Meningitis?

Case Scenario 1• 30-year-old man presents to emergency

department (ED)

• 24-hour history of chills and a stiff neck

• Afebrile with normal mental status

• Full neck flexion but with cervical pain

• Kernig and Brudzinski signs absent

increasing impactIncreasing impact

LR: Impact on Likelihood of Disease

LR = 1

No

Impact on Likelihood of

Disease

0

LR = 0.3

Less

Likely

LR = 0.2

Less

Likely

LR = 0.1

Less

Likely

LR = 0.01

Less

Likely LR = 3

More

Likely

LR = 5

More

Likely

LR = 10

More

Likely

LR = 100

More

Likely

Finding LR+ (95% CI) LR– (95% CI)

Fever 0.82 (0.62-1.1) 1.2 (0.94-1.5)

Kernig sign (Thomas) 0.97 (0.27-3.6) 1.0 (0.94-1.1)

Kernig sign (Uchihari) 4.2 (0.23-77) 0.92 (0.81-1.0)

Brudzinski sign 0.97 (0.26-3.5) 1.0 (0.94-1.1)

Jolt accentuation 2.4 (1.4-4.2) 0.05 (0.01-0.35)

Test Characteristics: Examination

Likelihood Ratios From Prospective Studies

1% Pretest probability in population presenting to ED

If positive, posttest probability = 2%

Jolt accentuation test

LR+ = 2.4

Jolt accentuation test

LR– = 0.05If negative, posttest probability < 0.1%

Likelihood Ratio

Caso I

• Paciente de 33 años, mujer,• Cefalea holocraneal• Características del dolor: no bien

definido• Fotofobia• Fonofobia• Náuseas• Empeora con el esfuerzo físico

Caso II

• Paciente mujer de 42 años, que mientras practica carrera de fondo siente dolor súbito frontoparietal muy intenso desde el inicio.

• No refiere antecedentes personales ni familiares de interés.

• Consciente en todo momento con sensación de dolor grave.

Caso III

• Cefalea crónica diaria• Mujer de 52 años• Abuso de analgésicos• Debuta con diplopid y afasia.

NO OLVIDEN LIKELIHOOD RATIO