Background: Newborn screening for CAH is effective in identifying the severe cases; however, the high rate of false-positive (FPR) results remains an important issue. Therefore, positive neonatal results must be confirmed by serum 17OHP levels, which present a great overlap among all forms.
Objective and hypotheses: To evaluate the utility of molecular analysis to improve CAH diagnosis in NBS program.
Method: Between 1999 and 2014, 86 newborns (NB) were submitted to DNA analysis due to positive tests for CAH in NBS program of Goias State Brazil. Neonatal 17OHP levels were measured by IFMA assay and adjusted for birth-weight. Confirmatory tests included serum 17OHP, androstenedione, testosterone measurements. CYP21A2 genotypes were determined by allele-specific PCR and large gene rearrangements by MLPA technique; entire CYP21A2 sequencing was performed when at least one allele remained with no mutation identified.
Results: 46 NBs presented symptoms of CAH, 42 of them had genotypes predicting severe classical forms. The other four were a girl with NC genotype and three NBs with normal genotype, one premature girl with pseudo-virilized genitalia and two males with loss of weight and vomiting due to other neonatal disease. Forty patients were asymptomatic, among them seven males were identified with the classical form genotype. Thirty-three non-affected patients were prevented to receive unnecessary treatment and among them, the 16 with normal genotype, were discharged from follow-up. A great overlap of 17OHP levels among all genotypes was observed. Among affected newborns, mutations derived from pseudogene events were found in 88% of the alleles: 13% carried large gene rearrangements and 87% point mutations. Novel mutations, not derived from pseudogene, were found in 12% of the alleles, all presented with gene founder effect.
Conclusion: We demonstrated that molecular testing was a useful supplemental tool identifying false-positive results in CAH-NBS, preventing unnecessary follow-up of newborns with inconclusive hormonal tests.
10 - 12 Sep 2016
European Society for Paediatric Endocrinology