SKRINING
SAWITRI
V
POPULASI  perkembangan dari sehat menjadi sakit yang
berbeda derajat beratnya
Populasi total
AT RISK!!
Sakit
Mencari pengobatan
Rawat inap
Meninggal
SKRINING
UJI DIAGNOSTIK
A study 
accurate test
Comparing with
GOLD STANDAR
Program
Dx dini penyakit di
komunitas
Terapi
Mencegah penularan
Mencegah kecacatan
PENELITIAN SKRINING
(UJI DIAGNOSTIK)
Skema Uji DIAGNOSTIK
“Healthy Sample”
Negative
Confirm Dx
Not sick
TRUE
NEGATIVE
Positive
SCREENING TEST
Confirm Dx
Sick,
FALSE
NEGATIVE
Sick,
TRUE
POSITIVE
Not Sick
FALSE
POSITIVE
AKURASI
1. VALIDITAS
Sensitivitas
Spesifisitas
Nilai Prediktif
Likelihood Ratio
2. RELIABILITAS
Persentase
(%)
• Sensitivitas
Kemampuan tes untuk menunjukkan
secara benar orang-orang yang benarbenar sakit
TP
TP + FN
• Spesifisitas
Kemampuan tes menunjukkan
secara benar orang-orang yang
benar-benar tidak sakit
TN
TN + FP
STANDAR BAKU
S
K
R
I
N
I
N
G
POSITIVE
NEGATIVE
TOTAL
DISEASE
NO DISEASE
TRUE
POSITIVE
FALSE
POSITIVE
(TP)
(FP)
FALSE
NEGATIVE
TRUE
NEGATIVE
(FN)
(TN)
TP + FN
FP + TN
JUMLAH
TP + FP
FN + TN
N
NILAI PREDIKTIF
1. Positif
2. Negatif
• PV positif:
Proporsi orang yang benar-benar sakit
setelah mendapatkan hasil tes positif
=
TP
TP + FP
PV Negatif
– Proporsi orang yang benar-benar tidak
sakit setelah mendapatkan hasil tes
negatif
TN
=
TN + FN
Faktor-faktor yang mempengaruhi
nilai prediktif
• Sensitivitas dan spesifisitas
• Prevalensi penyakit yang asimtomatis
 semakin tinggi prevalensi
penyakit, nilai prediktif positif akan
semakin tinggi
TES DENGAN DATA
KONTINYU (INTERVAL)
CUT OFF POINTS
• Tes dengan > 2 kategori hasil
• Contoh: Glaukoma
• Tes X :
– 1. GLAUCOMA
– 2. Tidak GL.
• Test Y:
– 1. TIO > 26
– 2. TIO 22 – 26
– 3. TIO < 22
Lanjutan …..Cutoff points
SENS?
SENS?
SPEC?
SPEC?
Healthy
Sick
22
Intra Occular Pressure
26
MENINGKATKAN AKURASI
• SEQUENTIAL (2-STAGE) TESTING
– Melakukan tes tambahan pada hasil yang sudah
positif
– Meningkatkan spesifisitas
• SIMULTANEOUS TESTING
– Melakukan dua tes secara bersamaan pada populasi
– Meningkatkan sensitivitas
RELIABILITAS
• Kemampuan alat untuk menunjukkan
hasil yang konsisten ketika digunakan
lebih dari satu kali pada individu yang
sama pada situasi yang sama
• Jika suatu tes
Valid
: pasti reliabel
Reliabel
: tidak selalu valid
Tidak reliabel : pasti tidak valid
Contoh :
Roni dengan hasil BSN/GTT (standar) telah didiagnosis diabetes
Tes Urine:
Px 1 (-)
Px 2 (+)
Px 3 (+)
Px 4 (-)
Tes Urine:
Px 1 (-)
Px 2 (-)
Px 3 (-)
Px 4 (-)
TIDAK RELIABEL
RELIABEL TAPI
TIDAK VALID
Faktor-faktor:
• Variasi tes
– Stabilitas reagen
– Fluktuasi sample atau spesimen
• Variasi pengamat
– Inter observer
– Intra observer
PROGRAM SKRINING
• Population-based screening is where a
test is offered systematically to all
individuals in the defined target group
within a framework of agreed policy,
protocols, quality management, monitoring
and evaluation.
• Opportunistic case-finding occurs when
a test is offered to an individual without
symptoms of the disease when they
present to a health care practitioner for
reasons unrelated to that disease
WHO PRINCIPLES OF EARLY DISEASE
DETECTION
Condition
• The condition should be an important health problem.
• There should be a recognisable latent or early symptomatic stage.
• The natural history of the condition, including development from latent to
declared disease should be adequately understood.
Test
• There should be a suitable test or examination.
• The test should be acceptable to the population.
Treatment
• There should be an accepted treatment for patients with recognised disease.
Screening Program
• There should be an agreed policy on whom to treat as patients.
• Facilities for diagnosis and treatment should be available.
• The cost of case-findings (including diagnosis and treatment of patients
diagnosed) should be economically balanced in relation to possible expenditure
on medical care as a whole.
• Case-findings should be a continuing process and not a ‘once and for all’ project.
Skema PROGRAM SKRINING
“Penduduk sehat”
Negatif
“SEHAT”
Positif
Tes Skrining
Konfirmasi Dx
Sakit,
TRUE
POSITIVE
Tidak sakit
FALSE
POSITIVE
CRITERIA TEST TO BE MET
• is highly sensitive and is highly specific.
• is validated and safe.
• has a relatively high positive predictive value and has a
relatively high negative predictive value.
• is acceptable to the target population including important sub
groups such
• as target participants who are from culturally and linguistically
diverse
• backgrounds, people from disadvantaged groups, and people
with a disability.
• There are established criteria for what constitutes positive and
negative test results,
• where a positive test result means that the person needs
further investigations, and a negative test result means the
person is rescreened at the usual interval, where applicable.
TES MANA YANG HARUS DIPILIH?
• SENSITIVITAS DAN SPESIFISITAS
• SUMBER DAYA YANG TERSEDIA
• DAMPAK
TES MANA TIDAK TERBUKTI
EFEKTIF?
• http://www.racgp.org.au/redbook/15
PROGRAM SKRINING
SEDERHANA
• Skrining depresi usila  GDS 15
• Obesitas  IMT
• ????