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Page 2 of 10 Gonzaga-Jauregui et al. Rare Dis Orphan Drugs J 2024;3:16 https://dx.doi.org/10.20517/rdodj.2024.02

THE PAST AND PRESENT OF NEWBORN SCREENING IN MEXICO AND LATIN AMERICA
Newborn screening (NBS) is a public health strategy aimed at identifying, in the first days of life, serious
conditions that may affect the survival or health of a child, and where early diagnosis and treatment result in
improved health outcomes, thus reducing morbidity, disability, and mortality. Although established in 1963
with the first mandated screenings done for phenylketonuria (PKU) in the United States, the
implementation of NBS around the world is very heterogeneous. In Latin America, the implementation of
NBS programs is unequal and inconsistent. Only 16 of the 33 countries in the region currently have a
national NBS program and the number of conditions included varies widely across countries from one
condition, namely congenital hypothyroidism (CHT) being screened in 16 countries, up to 29 conditions
[1,2]
screened for in Costa Rica [Table 1] . The development of tandem mass spectrometry (MS/MS)
technologies enabled the screening of dozens of metabolites in a single assay, expanding the capabilities of
classical biochemical NBS to include disorders of the metabolism of amino acids, organic acidemias, and
fatty acid oxidation disorders . Unfortunately, the adoption of MS/MS technologies for expanded newborn
[3]
screening (ENBS) in Mexico and Latin America is still lagging behind by decades, with only Costa Rica and
[1,2]
Uruguay having national ENBS programs in the region and a few regional, state, or localized efforts in a
handful of countries. Economic conditions, outdated legislation and technology, and limitations on
coverage and accessibility have hindered the widespread adoption of NBS in the Latin American and
Caribbean (LAC) region. This has resulted in a considerable number of infants with rare diseases going
undiagnosed and untreated, resulting in preventable morbidity and mortality in these populations.

In Mexico, NBS was first implemented in 1974, being the first country in Latin America to adopt this public
health strategy to screen infants for PKU, CHT, and congenital toxoplasmosis. Due to technical difficulties
with the assay, testing for toxoplasmosis was dropped shortly after, whereas initial screening results for PKU
and CHT showed the success of the program. In 1977, the NBS program was paused, but reinstated in 1986.
In 1988, legislation was approved to make NBS mandatory in medical institutions nationwide for newborns.
However, despite the evidence supporting the importance of screening for PKU, this disorder was also
removed from the program due to the low number of positive cases detected in the Mexican population,
leaving the national NBS program to screen only for CHT . In 1998, the national NBS program was
[4]
expanded to include PKU, congenital adrenal hyperplasia (CAH), galactosemia (GAL), and biotinidase
deficiency (BTD) for all newborns in Mexico. Updated guidelines published in 2002 suggested the
expansion of NBS to test for additional disorders based on the recommendations of the National Center of
Epidemiological Surveillance (Centro Nacional de Vigilancia Epidemiológica); however, no official mandate
was established. New guidelines were published in 2012, emphasizing the importance of the expanded
metabolic newborn screening covering at least CHT, CAH, GAL, disorders of amino acid metabolism,
disorders of fatty acid metabolism, cystic fibrosis (CF), hemoglobinopathies, severe combined
immunodeficiency (SCID), and leaving the possibility open to include other disorders that represent a
public health problem. In January 2013, a Congress decree was published, establishing the mandatory
implementation of ENBS and ophthalmological screening for all Mexican newborns, as well as retinal and
hearing screening for premature newborns, to ensure integral childhood development and the prevention
and detection of hereditary and congenital conditions. Despite this, ENBS is still not implemented
nationally and the major public healthcare institutions continue to screen for only six conditions: CHT,
PKU, CAH, CF, GAL, and glucose-6-phosphate dehydrogenase deficiency (G6PDD) [2,4,5] . Individual
institutions and healthcare systems can include additional conditions to screen for based on their budget,
their technological and logistical capabilities, and other internal considerations as determined by
institutional review committees.