Screening programs for newborns

   Mass screening of infants for inherited metabolic diseases (IMDs), along with prenatal diagnosis and medical genetic counseling, is the basis for the prevention of hereditary diseases in human society. According to the WHO definition, "screening" means the possible detection of a previously undiagnosed disease by means of tests, examinations or other procedures that provide a quick response. The main goal of primary screening for CVD is to identify healthy individuals and select those for further diagnosis. Programs for the primary biochemical diagnosis of hereditary diseases can be mass and selective.
   
    Mass testing is one of the fundamental innovations in the practice of world health care of the XX century and is characterized by the following:

1. Unselective approach to the examination.

2. Preventive nature of the survey.

3. Mass nature of the survey.

4. Two-stage nature of the examination: screening does not allow to establish a definitive diagnosis, but only identifies possible patients who should be re-examined and whose diagnosis should be confirmed.

  Thus, screening is an examination of contingents in order to divide them into groups with a high and low probability of disease.

  Hereditary metabolic diseases included in screening programs are selected according to the following criteria:

1. Diseases that lead to a pronounced decrease in working capacity and vitality without timely detection and treatment.

2. Diseases that are quite common in the population (frequency of at least 1:50,000-200,000 infants).

3. Diseases that can be treated with fundamental success for the patient and for which effective methods of prevention have been developed.

4. Diseases for which an adequate screening test has been developed.

 Phenylketonuria, hypothyroidism, and less precisely adrenogenital syndrome (congenital adrenal hyperplasia) and galactosemia meet these criteria in European populations.

    Mass screening involves screening all infants with simple diagnostic tests. Selective screening is usually carried out among special populations of mentally retarded children, children with visual, hearing, speech, musculoskeletal disorders, and those at risk for SIDS identified during mass screening. Selective diagnostic programs involve checking biochemical metabolic abnormalities (urine, blood) in patients suspected of having genetic hereditary diseases. Selective programs can use simple qualitative reactions (e.g., ferric chloride test for phenylketonuria or dinitrophenyl hydrazine test for keto acids) or more precise methods that can detect large groups of abnormalities. For example, thin-layer chromatography of urine and blood can be used to diagnose inherited disorders of amino acid, oligosaccharide, and glycosaminoglycan (mucopolysaccharide) metabolism. Gas chromatography is used to detect hereditary diseases of organic acid metabolism. Hemoglobin electrophoresis is used to diagnose the entire group of hemoglobinopathies. For in-depth biochemical analysis - from the quantification of a metabolite to the determination of enzyme activity (using native tissues or cultured cells), for example, using fluorometric techniques.

    Indications for the use of biochemical diagnostic methods in infants include symptoms such as convulsions, coma, vomiting, hypotension, jaundice, specific odor of urine and sweat, acidosis, disturbed acid-base balance, and growth failure. In children, biochemical methods are used in all cases of suspected hereditary metabolic diseases (delayed physical and mental development, loss of acquired functions, clinical picture specific to the hereditary disease).

    Biochemical methods are used to diagnose hereditary diseases and heterozygous conditions in adults (hepatolenticular degeneration, alpha-1-antitrypsin deficiency, G-6-FD deficiency, etc.)