The beginning of screening of 58 neonatal metabolic disorders in Iran (Part 1 - Generalities)

The beginning of screening of 58 neonatal metabolic disorders in Iran (Part 1 - Generalities)

Introduction

Neonatal screening began in 1960 with the invention of the Gatri test. The basis of this test is the growth of a specific bacterium in normal culture media in the presence of high levels of phenylalanine in the baby's blood sample. An increase in this substance in the baby's blood leads to phenylketonuria (a type of mental retardation). It is called phenylketonuria. For years, phenylketonuria, congenital hypothyroidism, and several other limited diseases were the only diseases included in screening programs.

Since about 2000, with the use of the MS / MS technique (Tandem Mass Spectrometry), a large number of biochemical abnormalities have been identified using a small amount, and since then screening programs have been widely used in the United States, Australia, and the United States. Europe has begun.

In developed countries, twenty-nine diseases (twenty-two of which are inherited metabolic diseases) are currently included in the neonatal screening program. Twenty-two other metabolic diseases can be diagnosed with this initial screening. Other diseases are candidates to be added to the list of screening diseases.

In other countries, 5 to 30 diseases are considered in neonatal screening. The benefits of extensive screening for infants are that they avoid avoidance of diagnosis or late diagnosis of many diseases, and that many cases of death or severe disability are prevented. In many cases, screen-detected diseases can be treated and controlled simply by modifying diets.

Infant screening has been shown to be effective in improving the prognosis of many metabolic disorders. However, there is still disagreement over the range of diseases to be screened (this is due to the lack of sufficient statistics).

Unlike conventional screening methods, MS / MS does not measure a single substance, but identifies a set of metabolites and determines the amount. Assessments on the small amount of blood taken from the baby's sole of the foot on a special filter paper are performed by the MS / MS system and can measure 60-45 different substances and the ratio between them and provide sufficient information to determine the limits. Provide 60 metabolic diseases. Of course, interpreting this information is very complicated and difficult.

Infant screening protocols should be prompt, affordable, and feasible for all infants across the country.



Disorders examined

Many of the nutrients that enter the body must be burned in specific ways to be able to: both provide the energy needed for cell activity and provide the nutrients needed for cell and tissue repair. These pathways are called the body's metabolic pathways, which vary depending on the raw material from which they are produced or burned. Such as: metabolic pathways of sugars, proteins, fats and nucleic acids. These pathways contain compounds called enzymes that can accelerate the conversion of one substance into another. Deficiency of these enzymes can lead to a wide range of diseases.

Diseases diagnosed with this screening include:

1- Disorders that are determined based on the molecular mass measurement of materials using MS / MS technique.

2- Disorders that are determined based on the safety properties of the materials.



The first group of disorders can include the measurement of substances associated with enzyme deficiency in metabolic pathways. like the:



1- Amino acid profile (MS / MS measurement method)

1-1- Urea cycle disorders

1-2- Disorders of amino acids



2- Asyl carnitine profile (MS / MS measurement method)

2-1- Fatty acid disorders

2-2- Organic acid disorders



3- Other disorders

Other disorders that are examined based on immune responses include favism, congenital hypothyroidism, congenital adrenal insufficiency, galactosemia, and biotinidase deficiency.



Sampling conditions

Screening tests should be performed after 48 hours and at most one week after birth (at least 36 hours after breastfeeding).

n Screening test on the first day of birth is unreliable and should be repeated.

Collecting a sample of an infant who is not breastfeeding may lead to false-negative results on the screening test. This is especially important for phenylketonuria and galactosemia. In these infants, re-sampling after breastfeeding is essential.

n Serum feeding the baby affects the results of screening tests.

n The baby should not be breastfed for 2 to 3 hours before the test, it is important to follow this time to get the right result.

n Blood samples should be taken from the baby's heel and on special filter paper.

n Premature infants (weighing less than 1,500 g) or the patient should have a sample taken on days 3 to 5 and a sample taken at one month of age (weighing more than 2 kg) or hospital discharge.

n If in a premature infant the result of a screening test is abnormal and the infant has certain clinical symptoms, the test should be repeated immediately to confirm the disease.

n In premature infants, physiological increases of 17-hydroxyprogesterone and decreased thyroxine may be observed.