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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