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Screening Tests &Interpretation

Terms in this set (31)

Goal of Health Promotion ?
optimize overall health
Goal of Dz Prevention :
Reduce occurrence and impact of specific diseases
Levels of dz prevention ?
◾1° Prevention
◾2° Prevention
◾3° Prevention
1° Prevention* Dfn&Intent
-Dfn : Implemented before there is evidence of dz or injury .
-Intent : Risk Reduction
2° prevention* Dfn& Intent
-Dfn : Implemented after dz has begun but before it's symptomatic .
-Intent :
1)Reduce consequences of dz .
2)Identification of dz in its early stages .
3)Intervening w/ a tx which is more effective Bcz it's being applied earlier .

((Can't reduce dz incidence))
Screening Dfn ?
Testing of apparently healthy populations to identify previously undiagnosed/Unrecognized dz's .
Objectives of Screening ?
◾To ensure early detection of a dz among individuals, so that prompt tx may be instituted > Prescriptive Screening
◾ To protect the community from dz that the person being screened has > Prospective Screeningg*
◾ For entry into certain forms of occupations
Screening Program Dfn ?
Comprehensive dz control activity based on the identification and tx of persons w/ either unrecognized dz or unrecognized risk factors for dz
The 2 approaches of screening :
◾Population-Level screening :National level policy decision to offer mass screeningg* to a whole sub-group of a population .
◾Individual-level screening(Case Findingg*) :Occurs at the individual patient-physician level بين المريض والدكتور
Case Finding is defined as ?
Special clinical efforts to recognize dz among persons who consult a health professional.
Effective Screening :
Involves both diagnostic
and treatment components.
The period b/w when early detection by screening is possible and when the clinical dx would normally have occurred , this definition best describes ?
Pre-clinical Phase
The amount of time by which dx is advanced or made earlier is called ?
Lead Time
Lead time is _____________ condition for effective screening .
A. Necessary but not sufficient
B.Necessary and sufficient
C.Neither necessary nor sufficient
D.Sufficient but not necessary
yield of a screening test , depends on ?
-Sensitivity of a test
-Prevalence of dz
-Availability of medical care
The screening test must be 'efficient' , this means ___?
The amount of inputs (in terms of expenses and time) should result in reasonable amount of outputs in terms of improved health & satisfaction.
Principles of screening :
1)Choice of dz for which to screen
2)Nature of screening test to be used
3)Availability of tx
4)Relative costs of screening
Examples of screening tests
1)Pap smear > Cervical cancer
2)Assessment of Bp and Ch levels > development of CVDs
3)Pregnancy tests
Logic of screening :
Sensitivity of a test :
freq of +ve test results in pts w/ a particular dz .
Formula used to calculate test sensitivity :
Test specificity
Freq of -ve test results in pts w/o the dz
Positive predictive value
the % of pts w/ a +ve test, who really have the dz .

Formula :
TP/TP+FP
Negative predictive value
The % of pts w/ a -ve test, who really don't have the dz

Formula :
TN/TN+FN
Prevalence of dz
Proportion of persons w/ dz in the pop
((y3ni we take into account kul el dz'ed pts yli home TP , FN / all pop))
prevalence formula
(TP + FN) /(TP+FN+FP+TN)
Sensitivity formula
TP/(TP+FN)
specificity formula
TN/(TN+FP)
Accuracy formula
(TP + TN)/(TP + TN+ FP + FN)
Accuracy vs. Precision
accuracy: how close experimental value is to accepted(true) value;
precision: how closely measured values agree with each other
Ideal test properties :
High Validity , High Precision
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