Diagnostic test

A diagnostic test gathers evidence to determine whether a disease is present, often in someone with symptoms or an abnormal screening result.

Sensitivity and specificity: Measures of a test’s ability to identify people with and without a target condition. These measures describe how often the test correctly detects disease or rules it out.
Differential diagnosis: The process of identifying and comparing possible causes of a patient’s signs and symptoms. Tests help distinguish among the conditions considered for a presentation.
Screening test: A test applied to people without symptoms to identify those who may have a condition. Screening finds possible cases; diagnostic tests investigate suspected disease.
Overtesting: The use of tests that are unnecessary or unlikely to improve health outcomes. Testing without likely benefit can produce costs, false alarms, and downstream procedures.
Likelihood ratio: A ratio that summarizes how much a test result changes the odds of a condition. Likelihood ratios show how strongly a result shifts diagnostic probability.
Clinical decision rule: A tool combining clinical features to estimate risk or guide a healthcare decision. Rules can identify who needs further diagnostic testing.
False positive: A positive test result in someone who does not have the target condition. False positives can prompt unnecessary follow-up or treatment.
Choosing Wisely: A campaign encouraging conversations about avoiding unnecessary medical tests and treatments. It addresses the problem of low-value diagnostic testing.
Bayes' theorem: A rule for updating the probability of a hypothesis using new evidence. It combines test performance with the probability of disease before testing.
Imaging: Techniques that create images of internal body structures for clinical evaluation. Imaging tests provide anatomical evidence for diagnosing many conditions.

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