Screening for Congenital Adrenal Hyperplasia: The Delfia Screening Test Overestimates Serum 17-Hydroxyprogesterone in Preterm Infants

Abstract

Objective. To compare 17-hydroxyprogesterone (17-OHP) levels measured by quantitative serum radioimmunoassay (RIA), including an extraction step, and by screening fluoroimmnoassay (FIA) on blood spots in preterm infants. Methods. Subjects were 39 healthy infants born at less than 31 weeks' gestational age. Each infant had weekly blood sampling, and RIA and FIA were performed on each sample. Results. Two hundred twenty-seven samples were taken at 28 to 41 weeks' postconceptional age. Mean ± SD 17-OHP measured by RIA was 11.4 ± 11.1 nmol/L (0.4 ± 0.4 µg/dL), and decreased over time. Mean ± SD 17-OHP measured by FIA was 38.96 ± 37.3 nmol/L, greater than 17-OHP (RIA). Log(δFIA-RIA) was inversely related to postconceptional age (R2 = .39). Conclusion. Screening FIA of blood spots overestimates levels of 17-OHP in preterm infants and should not be used to determine the likelthood of congenital adrenal hyperplasia in this population. We have abandoned FIA screening for congenital adrenal hyperplasia in infants weiging less than 1500 g.

Congenital Adrenal Hyperplasia—Current Insights in Pathophysiology, Diagnostics, and Management

“…There may be additional substances in dried blood spots that interfere with immunoassays (matrix effect) (287). The DELFIA was reformulated in late 2009 to make it less sensitive to cross-reacting compounds in premature infants (288). This modification improved the positive predictive value from 0.4% to 3.7% for the first screen (249).…”

Analysis of a pitfall in congenital adrenal hyperplasia newborn screening: evidence of maternal use of corticoids detected on dried blood spot

“…Moreover, the current FIA screening method looks for only the 17-OHP level, whereas with LCMS/MS we have an additional level of information for other steroid species, such as 21-DF ( 19 , 20 ). We present here a proof of concept that LC-MS/MS steroid profiling (including at least 17-OHP, 21-DF, testosterone, and D4-androstendione) may be useful for detecting not only false positive, as described elsewhere ( 9 , 10 ) but also false negative CAH cases.…”

“…In our NBS, we reported that 87.0 and 78.2% of results were false positive for the Ile-de France (IdF) region in 2019 and 2020, respectively, with positive predictive values (PPVs) of 12.0 and 16.1%, respectively. Different factors could explain such a low PPV: (i) cross-reactive detection of 17-OHP with its steroid precursors and their sulphated conjugates, which are present in the first 48 h after birth, and longer in preterm neonates ( 8 , 9 ); (ii) increased 17-OHP levels due to illness, stress, and biological variation ( 8 , 10 ); (iii) the presence of high levels of delta-5 steroids, such as pregnenolone (Preg) and 17-hydroxypregnenolone (17OHPreg) in premature newborns due to immature adrenal function. These factors make it difficult to define a predictive threshold ( 8 , 9 ) and result in anxiety for the parents during the recall process.…”

“…Different factors could explain such a low PPV: (i) cross-reactive detection of 17-OHP with its steroid precursors and their sulphated conjugates, which are present in the first 48 h after birth, and longer in preterm neonates ( 8 , 9 ); (ii) increased 17-OHP levels due to illness, stress, and biological variation ( 8 , 10 ); (iii) the presence of high levels of delta-5 steroids, such as pregnenolone (Preg) and 17-hydroxypregnenolone (17OHPreg) in premature newborns due to immature adrenal function. These factors make it difficult to define a predictive threshold ( 8 , 9 ) and result in anxiety for the parents during the recall process. For preterm babies, the cut-off value of the FIA has to be adapted to gestational age and weight ( 9 , 11 ).…”

“…These factors make it difficult to define a predictive threshold ( 8 , 9 ) and result in anxiety for the parents during the recall process. For preterm babies, the cut-off value of the FIA has to be adapted to gestational age and weight ( 9 , 11 ). Some countries use LC-MS/MS as a second-tier approach for DBS analysis related to CAH to reduce false positives , although France has not proposed this yet ( 5 , 12 ).…”