Triagem neonatal para hiperplasia adrenal congênita: experiência do estado do Rio de Janeiro

Neonatal 17-hydroxyprogesterone levels adjusted according to age at sample collection and birthweight improve the efficacy of congenital adrenal hyperplasia newborn screening

INTRODUCTION

The primary concern related to congenital adrenal hyperplasia (CAH) newborn screening (NBS) is the high rate of false-positive results (FPR) associated with prematurity; false-negative results (FNR) can also occur due to precocious sample collection.

OBJECTIVE

To determine the neonatal 17-hydroxyprogesterone (N17OHP) normal range in newborns in Sao Paulo using different references according to age and birthweight (BW) and to establish the optimal NBS cut-off levels.

METHODS

Neonatal 17-hydroxyprogesterone levels from 271 810 newborns (NBs) according to sample collection time (G1: 48-<72 h and G2: ≥72 h) and BW (≤1500 g, 1501-2000 g, 2001-2500 and >2500 g) were evaluated. N17OHP was measured by an fluoroimmunoassay, and serum 17OHP was measured by liquid chromatography-mass spectrometry. Affected and asymptomatic NBs with persistently increased 17OHP levels were submitted to CYP21A2-sequencing.

RESULTS

Neonatal 17-hydroxyprogesterone levels in G1 were lower than G2 in all BW groups (P < 0·001). The FPR rate in G1/G2 was 0·2% using the 99·8th and 0·5% using the 99·5th percentile. The 99·8th percentile N17OHP value was the best cut-off for distinguishing between unaffected and affected NBs. Forty-four salt wasters, and five simple virilisers were diagnosed; N17OHP levels ranged from 93·3 to 2209·8 nmol/l, and no affected neonates with FNR were identified. The positive predictive value in G1 and G2 using the 99·8th percentile was 5·6% and 14·1%, respectively, and 2·3% and 7%, respectively, using the 99·5th percentile. Molecular tests identified two NBs with the nonclassical form among the 29 FPR.

CONCLUSION

Neonatal 17-hydroxyprogesterone levels adjusted to sample collection age and birthweight reduced the FPR, and the use of N17OHP values based upon the 99·8th percentile improved the NBS efficacy.

Molecular analysis of CYP21A2 can optimize the follow-up of positive results in newborn screening for congenital adrenal hyperplasia

Neonatal screening for congenital adrenal hyperplasia (CAH) is useful in diagnosing salt wasting form (SW). However, there are difficulties in interpreting positive results in asymptomatic newborns. The main objective is to analyze genotyping as a confirmatory test in children with neonatal positive results. Patients comprised 23 CAH children and 19 asymptomatic infants with persistently elevated 17-hydroxyprogesterone (17OHP) levels. CYP21A2 gene was sequenced and genotypes were grouped according to the enzymatic activity of the less severe allele: A1 null, A2 < 2%, B 3-7%, C > 20%. Twenty-one children with neonatal symptoms and/or 17OHP levels > 80 ng/ml carried A genotypes, except two virilized girls (17OHP < 50 ng/ml) without CAH genotypes. Patients carrying SW genotypes (A1, A2) and low serum sodium levels presented with neonatal 17OHP > 200 ng/ml. Three asymptomatic boys carried simple virilizing genotypes (A2 and B): in two, the symptoms began at 18 months; another two asymptomatic boys had nonclassical genotypes (C). The remaining 14 patients did not present CAH genotypes, and their 17OHP levels were normalized by 14 months of age. Molecular analysis is useful as a confirmatory test of CAH, mainly in boys. It can predict clinical course, identify false-positives and help distinguish between clinical forms of CAH.