Screening for genetic diseases - general principles. Newborn screening. Prenatal screening (BCS and NIPT). Heterozygote carrier screening.
Genetic screening is the systematic testing of apparently healthy individuals or populations to identify those at increased risk of a genetic disease.
Screening does not confirm a diagnosis. Its role is to select individuals who need further diagnostic testing.
Screening vs Diagnostic Testing
- Screening → estimates risk, applied to populations
- Diagnostic testing → confirms disease, applied to individuals at risk
This distinction is fundamental and frequently tested in exams.
I. GENERAL PRINCIPLES OF GENETIC SCREENING
A genetic screening program is justified when:
- the disease is serious and clinically significant,
- the disease has a detectable preclinical phase,
- early detection improves outcome,
- effective treatment or intervention exists,
- the screening test is safe, acceptable, accurate, and affordable,
- confirmatory diagnostic methods are available.
Key Test Characteristics
Sensitivity
- Ability of the test to correctly identify affected individuals.
Specificity
- Ability of the test to correctly identify unaffected individuals.
Predictive Values
- Positive predictive value (PPV): probability that a positive result is true.
- Negative predictive value (NPV): probability that a negative result is true.
Predictive values depend on disease prevalence.
Ethical and Social Considerations
- Informed consent
- Confidentiality
- Psychological impact
- Avoidance of stigmatization or discrimination