CRP - K10 - Diagnosis
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Transcript of CRP - K10 - Diagnosis
DIAGNOSISPutri Eyanoer, MD.,Ms.Epi.,Ph.D
1. Disease confirmation2. To sort other possibilities ~ sensitivity and
specificity3. Screening purpose ~ searching asymptomatic
patients4. Therapeutic purpose ~ identification of disease and
complication, treatment and therapy options,prediction of prognosis, and confirmation of otherpositive result
5. Epidemiologic studies
Biologic onset of the condition
Pathologic evidence of disease detectable by screening
Sign and symptoms of disease
Health care sought
Diagnosis of disease
Treatment of disease
PHYSICAL EXAMINATION
ADDITIONAL EXAMINATION
ANAMNESE
ADDITIONAL EXAMINATION
SERIAL TESTING
SENSITIVITY ↓SPECIFICITY ↑
ADDITIONAL EXAMINATION
PARALEL
SENSITIVITY ↑SPECIFICITY ↓
POSITIVE
NEGATIVE
IDEALLY…
FALSE NEGATIVE
FALSE POSITIF
MORE OFTEN…
1. Simple, cheap and non-invasive
2. Earlier detection / diagnosis at an earlier stage
DISEASE
TEST RESULT
Yes No Total
Yes TP FP TP+FP
No FN TN FN+TN
Total TP+FN FP+TN Total
TP=True Positive ; FP=False Positive ; TN=True Negative ; FN=False Negative
Diseased
Healthy classified as diseased
(false positive)
Diseased classified as healthy
(false negative)
Classified asdiseased
Diseased classifiedas diseased
Population
MODEL FOR SENSITIVITY AND SPECIFICITY
Penyakit (+) Penyakit (-)
Test (+) aTrue Positive
bFalse Positive
Test (-) cFalse-Negative
dTrue Negative
ACCURACY OF A TEST RESULT
Penyakit (+) Penyakit (-)
Test (+) aTrue Positive
bFalse Positive
Test (-) cFalse-Negative
dTrue Negative
SENSITIVITY AND SPECIFICITY
aa + c
Sensitivitas =
Spesifisitas = db + d
x 100 %
x 100 %
SENSITIVITY AND SPECIFICITYEXAMPLE : BLOOD GLUCOSE LEVEL
Diabetes : + Diabetes : - TotalTest :+ 34 20 54
Test : - 116 9830 9946
Total 150 9850 10.000
Diabetes : + Diabetes : - TotalTest :+ 66 98 164
Test : - 84 9752 9836Total 150 9850 10.000
Tingkat Pemotongan : 130 mg/100 ml
Tingkat Pemotongan : 180 mg/100 ml
Sensitivitas =34/150 x 100 % = 22.6 %
Spesifisitas =9830/9850x 100 % = 99.7 %
Sensitivitas =66/150 x 100 % = 44 %
Spesifisitas =9752/9850x 100 % = 99 %
SENSITIVITY AND SPECIFICITY
Ca : + Ca : - Total
FNA : + 14 8 22
FNA : - 1 91 92
Total 15 99 114
Sensitivity = 1414 +1
x 100 % =93 %
Specificity = 9191 + 8
x 100 % =92 %
POSITIVE AND NEGATIVE PREDICTIVE VALUE
Ca : + Ca : - Total
FNA : + 14 8 22
FNA : - 1 91 92
Total 15 99 114
14 + 8
(PV+) = aa + b x 100 %
PV+ = 14 x 100 % = 64 %
(PV-) = dd + c x 100 %
9191 + 1 x 100 % = 99 %PV- =
SUMMARY TABLE
SENSITIVITY SPECIFICITY PPV NPV
Proportion of patients with the target of disorder who had a positive test result
Proportion of patients with the target disorder who had a negative test result
Proportion of patients with positive test results who have the target disorder
Proportion of patients with negative test results who do not have the target disorders
Ability to detect disease Ability to detect that a healthy person among sick ones
Probability of disease in a patient with (+) test result
Probability of not having the disease when the test result is (-)
Should give (+) result among unhealthy group
Should give (-) result among healthy group
Chosen when there is important penalty for missing the disease (dangerous but treatable:tb,syphillis)
Used to confirm a diagnosis ~ needed when false(+) result can harm the patient (traumatic case, chemotherapy)
= A : (A+C) = D : (C+D) = A : (A+B) = D : (C+D)
POSITIVE PREDICTIVE VALUE
100
60
80
40
20
0 1/5 1/10 1/50 1/100 1/1000 1/10.000
SENSITIVITY/SPECIFICITY80/80
90/9099/99
PREVALENCE
PO
SIT
IVE
PR
ED
ICTI
VE
VA
LUE
(%)
LIKELIHOOD RATIOS
Define as :The PROBABILITY of that test result in people withdisease divided by the PROBABILITY of the test result inpeople without the disease
ODDS
Disease are MORE LIKELY in the presence of an extremely ABNORMAL TEST RESULT than it is for
marginal one
LIKELIHOOD RATIOS
POSITIVE LIKELIHOOD RATIO (LR+) Giving the magnitude of a possible positive test among those un-healthy compare to those healthy .
= { a/(a+c)} / {b/(b+d)} = SENSITIVITY / (1- SPECIFICITY)
NEGATIVE LIKELIHOOD RATIO (LR-) Giving the magnitude of a possible negative test among thoseun-healthy compare to those healthy
= { c/(a+c)} / {d/(b+d)} = (1- SENSITIVITY ) / SPECIFICITY
• Pd uji diagnostik kita menentukan bagaimana suatu uji dpt memisahkan antara subjek yg sakit dgn yg tdk sakit.
• CONTOH:
• Suatu uji diagnostik thd 100 pasien limfoma malignum yg dibuktikan dgn biopsi, 65 menunjukkan hasil positif; sdgkanuji diagnostik yg sama thd 100 pasien dgn pembesaran kelenjar non-limfoma, hanya 30 yg menunjukkan hasil uji positif. Bila dilakukan uji hipotesis dgn X2, tdpt hubungan yg bermakna (p<0,001) antara hasil uji positif dgn tdptnya limfoma malignum.
Penyakit
Hasil uji
Limfoma Non limfoma Total Positif PB
65PS30
PB+PS
Negatif NS35
NB70
NB+NS
Total PB+NS100
PS+NB100
Total200
Sensitivitas = A : (A+C) = 65 : 100 = 65%Spesifisitas = D : (B+D) = 70 : 100 = 70%
Histopatologi
Mammografi
Ca Non Ca JlhPositif 13 4 17Negatif 3 28 31
Jlh 16 32 48
SENSITIVITY: A/(A+C)
SPESIFICITY:D/(B+D)
LR+:SENS/
(1-SPEC)
LR-:(1-SENS)
/SPEC
PRE-TEST PROBABILITY
= PREVALENCE:(A+C ) / (A+B+C+D)
(13/16)X100%
= 81,25%
(28/32)X100%
=87,5%
(13/16)/(1-28/32)
=6,5
1-(13/16)/(28/32)
=0,21
16/48
= 33,3%
PRE TEST ODDS=PREVALENCE:
(1-PREVALENCE)
POST TEST ODDS=PRE TEST ODDS X LR+
POST-TEST PROBABILITY=POST TEST ODDS:
(1+POST TEST ODDS)
(16/48) : (1-16/48)
= 0,5
0,5 X 6,5
= 3,25
3,25 : (1+3,25) = 0.764 = 76,4%
Pretest probability Post test probability
33.3% 76.4%