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How are genetic screening tests different from genetic diagnostic tests?
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Testing

How are genetic screening tests different from genetic diagnostic tests?

Genetic screening estimates the risk of developing a condition, whereas diagnostic testing is used to confirm or rule out the presence of a specific genetic disorder.

Genetic Screening Tests

Screening tests are generally performed on individuals who do not show signs or symptoms of a disorder. They estimate whether an individual’s risk of having a condition is higher or lower than that of the general population.

  • Positive result: Indicates a higher-than-average risk, but does not confirm the presence of the condition.
  • Negative result: Indicates a lower-than-average risk.

Because these tests are estimates, they can produce false positives (indicating risk when the person is unaffected) or false negatives (indicating lower risk when the person is actually affected). Screening helps guide next steps, such as determining if diagnostic testing is necessary.

Genetic Diagnostic Tests

Diagnostic tests are typically used for individuals who exhibit signs or symptoms of a disorder. These tests are used to confirm or rule out suspected genetic conditions and can inform a person’s risk of developing a disease or passing it on to their children. Results from diagnostic tests guide healthcare choices and disorder management.

Examples of Genetic Tests

Genetic Screening Examples

  • Noninvasive prenatal testing (NIPT/NIPS): Performed before birth to determine the risk of chromosomal disorders like Down syndrome.
  • Newborn screening: Performed shortly after birth to assess the risk for more than 35 genetic conditions, often by analyzing protein and enzyme levels.

Genetic Diagnostic Examples

  • Molecular gene tests: Use DNA sequencing to determine the order of nucleotides in an individual's genetic code to identify disease-causing changes.
  • Chromosomal tests: Analyze whole chromosomes or long DNA segments to identify large-scale changes, such as an extra or missing chromosome (trisomy or monosomy).

Frequently Asked Questions

Screening tests are favored as initial steps because they are noninvasive, relatively inexpensive, and carry zero risk of physical complications for the patient or a pregnancy, requiring only a simple blood draw or heel prick. In contrast, many diagnostic tests are more expensive, take longer to process, or involve invasive procedures (such as amniocentesis, tissue biopsies, or bone marrow aspirations) that carry small procedural risks, making them appropriate only when risk factors or symptoms justify them.
In most cases, health insurance providers and Medicaid cover diagnostic testing when there is documented medical necessity, such as an abnormal screening result, an abnormal ultrasound, or a documented family history of a specific genetic condition. However, insurers often require prior authorization, clinical notes, and pre-test genetic counseling to confirm that the chosen test panel is appropriate and targeted to the suspected condition.
n abnormal or high-risk screening result, such as from noninvasive prenatal testing (NIPT), is not a final diagnosis. The standard next step is meeting with a genetic counselor or maternal-fetal medicine specialist to review the findings and discuss whether to proceed with diagnostic testing. Definitive confirmation typically requires procedures like chorionic villus sampling (CVS) or amniocentesis, which analyze actual fetal cells to confirm or rule out chromosomal differences before medical decisions are made.
Yes. While diagnostic tests directly sequence DNA or examine whole chromosomes to find pathogenic mutations, they can sometimes identify a variant of uncertain significance (VUS). A VUS is a change in the genetic code where current medical science cannot yet prove whether the alteration causes disease or is merely a harmless natural variation. In such cases, clinical correlation with symptoms, family variant tracking, and re-evaluating the variant over time are necessary.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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