Essence and two areas of genetic screening
The global goal of genetic screening boils down to the mass search within a large population for those individuals who possess a specific, clinically significant genotype. Depending on the ultimate goal, two main areas of diagnostics are distinguished:
- Search for inherited metabolic disorders. This is the basis of total neonatal screening. In this case, specialists look for a genotype that acts as the direct, immediate cause of the pathology.
- Testing for genetic predisposition. Within this approach, a genotype is identified that does not cause the disease directly, but creates an extremely high tendency (predisposition) for its manifestation in the future.
Why test outwardly healthy children?
The key feature of neonatal screening is that it is carried out at the preclinical stage. During this period, the infant looks completely healthy, and symptoms have not yet appeared.
If this stage is missed, the consequences will be fatal. Late diagnostics, when the clinical picture has already fully developed, inevitably leads to profound disability or death of the child. Conversely, the timely initiation of adequate pathogenetic therapy prevents the destructive action of the disease and ensures normal physical and neuropsychological development of the baby.
Criteria for selecting diseases for screening
Far from every genetic pathology is subject to mass screening. For a disease to be included in the screening panel, it must strictly meet two basic criteria:
- Medicine must have reliable, scalable, and financially accessible diagnostic tests to detect it.
- Effective treatment methods for this pathology must exist in clinical practice (there is no point in looking for a disease if modern science cannot offer therapy).
History and spectrum of tested diseases in Russia
The national newborn mass testing system developed in stages. The panel was expanded as new diagnostic capabilities emerged:
- Since 1985, detection of phenylketonuria began.
- Since 1993, diagnostics of congenital hypothyroidism was added to the program.
- Since 2006, the screening panel was expanded to five mandatory nosologies. Galactosemia, adrenogenital syndrome, and cystic fibrosis were additionally included.
Organization of biomaterial collection
The procedure is standardized and requires strict adherence to timelines and execution techniques.
Timing:
- For full-term infants, collection is performed on the 4th–5th day of life.
- For preterm infants — on the 7th day of life.
- Reserve timeline: if for any reason (e.g., early discharge) the test was not performed in the maternity hospital, it must be performed at the pediatric clinic, but strictly no later than the 14th day of life.
Methodology: A medical worker collects capillary blood from the newborn's heel. The blood is applied to special filter test strips (cards). The dried cards are promptly sent to a specialized genetic laboratory. A note indicating that screening was performed must be recorded in the child's medical birth record.
Physician's tactics upon detecting abnormalities
If the laboratory issues a dubious or initially positive result, this is not yet a definitive diagnosis. In such a situation, the action algorithm is as follows:
- An urgent repeat blood collection is organized to verify the result.
- If a positive result is confirmed on the repeat test, the family and child are referred for an in-depth specialized examination to establish a definitive diagnosis and immediately initiate therapy.
Class and exam questions
At what stage are pathologies detected during neonatal screening?
Pathologies are detected at the preclinical stage, when the newborn outwardly appears completely healthy and has no clinical symptoms.
What to do if the child is discharged from the maternity hospital before screening is performed?
If the test was not performed in the maternity hospital, capillary blood collection is carried out at the local outpatient clinic. This must be done within the reserve period — no later than the 14th day of the infant's life.
Where is the fact of blood collection for screening recorded?
A note regarding the procedure is mandatory made by the medical staff in the newborn's medical birth record.
What else to study on this topic
- Pathogenesis and clinical presentation of phenylketonuria
- Principles of early diagnostics of congenital hypothyroidism
- Galactosemia: mechanisms of development and dietary therapy
- Adrenogenital syndrome in newborns
- Cystic fibrosis: genetic basis and screening
- Organization of medical genetic counseling (MGC) services
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