ABSTRACT
Spinal muscular atrophy (SMA) is considered one of the most common autosomal recessive disorders, with an estimated incidence of 1 in 10,000 live births. Testing for SMA has been recommended for inclusion in neonatal screening (NBS) panels since there are several therapies available and there is evidence of greater efficacy when introduced in the pre/early symptomatic phases. In Brazil, the National Neonatal Screening Program tests for six diseases, with a new law issued in 2021 stating that it should incorporate more diseases, including SMA. In the present study, dried blood spot (DBS) samples collected by the Reference Services of Neonatal Screening of RS and SP, to perform the conventional test were also screened for SMA, using real-time PCR, with SALSA MC002 technique. A total of 40,000 samples were analyzed, enabling the identification of four positive cases of SMA, that were confirmed by MLPA. Considering our sampling, Brazil seems to have an incidence comparable to the described in other regions. This work demonstrated that the use of the MC002 technique in samples routinely collected for the conventional NBS program is suitable to screen for SMA in our conditions and can be included in the expansion of the neonatal screening programs.
ABSTRACT
Congenital adrenal hyperplasia (CAH) occurs due to enzyme defects in adrenal steroidogenesis. The 21-hydroxylase deficiency accounts for 90-95% of cases, triggering accumulation of 17-hydroxyprogesterone (17-OHP). Early diagnosis through neonatal screening allows adequate treatment and reduced mortality. The purpose of the study was to determine 17-OHP cutoffs for the diagnosis of CAH in a public newborn screening program in Southern Brazil. A retrospective, descriptive, cross-sectional study was conducted to analyze 17-OHP levels in dried blood samples collected on filter paper of 317,745 newborns screened at a public newborn screening center from May 2014 to April 2017. Neonatal 17-OHP was measured in DBS samples using a time-resolved fluoroimmunoassay (GSP® kit 3305-0010; PerkinElmer). Different cutoffs were determined and stratified by birth weight. The incidence of CAH was 1:15,887 live births in the state of Rio Grande do Sul, with 20 cases of classical CAH diagnosed during the study period. Most newborns (80.73%) were white, and the prematurity rate was 9.8% in the study population. The combination of different percentiles, 98.5th for birth weight 2001-2500 g and 99.8th for the other birth weight groups, decreased false-positive results and increased specificity compared with current reference values to identify classical CAH cases. The local 17-OHP cutoffs determined were higher than those currently used by this screening program for all birth weight groups. The calculation of reference values from local population data and the combination of percentiles proved to be a valuable tool for proper diagnosis of CAH and reduction in the number of false positives.
