A lot of times, we are confused between the major differences of Screening Tests and Diagnostics Tests.
The primary purpose of screening tests is to identify early risk factors for illness in people. Certain people may be completely unaware that they hold such a condition. It helps in detecting an early illness, at times, early enough to treat it most effectively or to reduce the risk of the disease. A screening test may require a diagnostic test after. The primary purpose is not so much about diagnosing a disease but to identify those people that may have it.
Blood pressure tests, routine EKGs, breast exams such as mammograms, digital rectal exams, routine blood tests, and urine tests,. Certain times questionnaires about behaviors and risk factors might be considered as screening tests.
The aim of diagnostic tests is the process of finding out if a patient has a specific disease or not. Doctors prescribe a test to determine the presence or absence of the possible illness in people as a basis for treatment choice. They are usually in symptomatic or screen positive people (confirmatory test). Diagnostic tests are testing that determines whether a condition is present with 100% accuracy
Mammography correlated with USG, Echocardiography, Complete Blood Count (CBC), Colonoscopy, Bone Density Study, Magnetic Resonance Imaging (MRI), CT or CAT Scan, Electrocardiogram (ECG), Prostate Specific Antigen (PSA Test).
|Screening Tests||Diagnostic Tests|
|Purpose||To find potential disease indicators||To establish presence/absence of disease|
|Target Population||large numbers of asymptomatic, but potentially at risk peoples||People with symptoms to establish a diagnosis or people with a positive screening test and need further correlation|
|Test Practice||Simple, acceptable to patients, usually cost effective||At times expensive, but justifiable as necessary to establish a diagnosis|
|Positive Result Threshold||
Generally chosen towards high sensitivity not to miss potential disease
|Chosen for high specificity (true negatives). More weight is given to accuracy and precision than to patient acceptability|
|Positive Result Threshold||
Indicates suspicion of disease (often used in combination with other risk factors) that warrants confirmation
|Result provides a definite diagnosis|
|Cost||Low Cost, benefits should justify the costs since large numbers of the patient will need to be screened, to identify a small number of potential cases||Comparatively little expensive associated with a diagnostic test may be justified to establish the diagnosis.|
The case finding could be a strategy for targeting resources at people or the group who seem to be at risk for a specific illness or disease. A regular health check-up in corporate companies such as Executive Package helps in targeting people who may be under stress.
Note the similarities to screening – each asks to risk stratify the population for more investigation.
We can say that Case Finding is a key strategy in disease irruption management (e.g. sexual partner ascertainment in social disease outbreaks; household/work contacts in food-borne outbreaks). The purpose is to find at-risk people and diagnose them by screening and other treatment if necessary.
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