screening 2015-16
TRANSCRIPT
PRESENT
SCREENING
“An Ounce of Prevention is
Worth a Pound of Cure” Benjamin Franklin
Prevention
Cure
SANI
PRIMARIA SECONDARIA TERZIARIA
A RISCHIO AMMALATI
ASSENZA DI PATOLOGIA
FASE ASINTOMATICA
FASE SINTOMATICA
SANI
Impedire nuovi casi di malattia
STRUMENTI
PRIMARIAASSENZA DI PATOLOGIA
Vaccinazione
Promozione della salute
Stili di vita
OBIETTIVO
SECONDARIAFASE
ASINTOMATICA
A RISCHIOPrevenire
la malattia nella popolazione a
rischio
STRUMENTI
Screening
Diagnosi precoce
OBIETTIVO
TERZIARIA
AMMALATI
FASE SINTOMATICA
Prevenire le complicazioni
e le invalidità
STRUMENTI
Riabilitazione
OBIETTIVO
PRIMARIA SECONDARIA TERZIARIAASSENZA DI PATOLOGIA
FASE ASINTOMATICA
FASE SINTOMATICA
inizio biologico patologia
fase clinicamente
manifesta
PRIMARIA SECONDARIA TERZIARIAASSENZA DI PATOLOGIA
FASE ASINTOMATICA
FASE SINTOMATICA
inizio biologico patologia
patologia diagnosticabile
decesso senza
screening
fase clinicamente
manifestadecesso
con screening
Detectable Pre-
Clinical Phase (DPCP)
DIAGNOSI PRECOCE
MIGLIORE RISPOSTA ALLA TERAPIA
RIDURRE LA MORBIDITÀ E LA MORTALITÀ
Detectable Pre-
Clinical Phase
(DPCP)
Patologie Severe
Trattamento precoce efficace
Alta Prevalenza
quando?
ECONOMICO
FACILE DA SOMMINISTRARE
POCO INVASIVO
AFFIDABILE
VALIDO
Screening
Test
TEST Accuracy
Sensitivity: probability that diseased people test +
Specificity: probability that not diseased people test -
Probability of correct test
TEST Performance
Positive predictive value: the probability that subjects with a positive screening test truly have the disease.
Negative predictive value: the probability that subjects with a negative screening test truly don't have the disease.
Probability of disease
NEGATIVE TEST
POSITIVE TEST
POSITIVE TEST
How likely is it that he really HAS the disease?
(How worried should he be?)
132 983
45 63.650
TESTPOSITIVE
TESTNEGATIVE
DISEASED NOT DISEASED
TRUE POSITIVE
TRUE NEGATIVE
TEST Performance
a
c
b
d
64.810SENSITIVITY = 74.6%SPECIFICITY= 98.5%
132 983
45 63.650
TESTPOSITIVE
TESTNEGATIVE
DISEASED NOT DISEASED
TRUE POSITIVE
TRUE NEGATIVE
TEST Performance
a
c
b
d
1.115
63.695
Positive Predicted Value = aa+b
1321.115 = 11.8 %
177 64.633 64.810
132 983
45 63.650
TESTPOSITIVE
TESTNEGATIVE
DISEASED NOT DISEASED
TRUE POSITIVE
TRUE NEGATIVE
TEST Performance
a
c
b
d
1.115
63.695
177 64.633 64.810
Positive Predicted Value = aa+b
1321.115 = 11.8 %
NEGATIVE TEST
How likely is it that he really does NOT have it?
(How reassured should he be?)
132 983
45 63.650
TESTPOSITIVE
TESTNEGATIVE
DISEASED NOT DISEASED
TRUE POSITIVE
TRUE NEGATIVE
TEST Performance
a
c
b
d
1.115
63.695
Negative Predicted Value = dc+d
63.65063.695 = 99.9 %
177 64.633 64.810
132 983
45 63.650
TESTPOSITIVE
TESTNEGATIVE
DISEASED NOT DISEASED
TRUE POSITIVE
TRUE NEGATIVE
TEST Performance
a
c
b
d
1.115
63.695
Negative Predicted Value = dc+d
63.65063.695 = 99.9 %
177 64.633 64.810
POSITIVE TEST
132 983
45 63.650
TESTPOSITIVE
TESTNEGATIVE
DISEASED NOT DISEASED
TRUE POSITIVE
TRUE NEGATIVE
TEST Performance
a
c
b
d
64.810SENSITIVITY = 74.6% SPECIFICITY= 98.5%
FALSE NEGATIVE
FALSE POSITIVE
FALSI NEGATIVI
• rassicurazione ingiustificata riguardo al proprio stato di salute,
• il referto negativo potrebbe ritardare la diagnosi effettiva di malattia.
effetti negativi
dello screening
effetti negativi
dello screening
FALSI POSITIVI
interventi non necessari
preoccupazioni e costi inutili, sia individuali sia sociali
diagnosi precoce = rischio di individuare e trattare lesioni che non si sarebbero mai manifestate clinicamente, determinando sovradiagnosi e sovratrattamento.
16% LIFETIME CHANCE OF DEVELOP A PROSTATE CANCER,
3% CHANCE OF DYING FROM IT
THE TEST IS HARDLY MORE EFFECTIVE THAN A COIN
TOSS
P.S.A. TESTING CAN’T DETECT PROSTATE CANCER
SCREENING DID NOT REDUCE THE
DEATH RATE IN MEN 55 AND OVER
AFTER TREATMENT FOR PROSTATE CANCER
IN MEN WITH A FAMILY HISTORY OF PROSTATE CANCER
quando?
30 MILLION TEST/YEAR
ANNUAL BILL = $3 BILLION
SENSITIVITY = 99.9% SPECIFICITY= 99.5%
PREVALENCE MATTERS!!!