Serum concentration of 17α-hydroxyprogesterone in children from birth to adolescence

Reference intervals (RI) of serum 17α- hydroxyprogesterone (17OHP) are useful to confirm congenital adrenal hyperplasia (CAH) in neonates with abnormal screening results and nonclassical forms of CAH in symptomatic children. We aimed to establish serum 17OHP RI in normal children and adolescents using a current 17OHP radioimmunoassay (RIA).

Serum 17OHP was measured via a current RIA (Diasource) in children, i.e. 111 infants aged <1 year [before (NE-17OHP) and after extraction (E-17OHP)] and 216 children aged 1-17 years. Forty NE serum samples from subjects aged >1 year, covering the whole analytical range, were simultaneously measured to compare 17OHP RIA from Diagnostic System Laboratories (DSL) (withdrawn) and Diasource by Passing Bablok linear regression and ratio plot. The equation obtained was used to correct our own previous RI (DSL RIA) for infancy for the Diasource RIA. Samples from infants aged <1 year were used to verify the calculated RI with evaluator protocol C28-A3. The influence of age, gender, and Tanner's classification (T) was assessed in children aged >1 year by ANOVA.

E-17OHP as measured via the Diasource RIA was significantly lower than NE-17OHP in infants aged <1 year (p < 0.0001). The 17OHP measurement from the Diasource RIA was negatively biased compared to the value obtained using the DSL RIA (Diasource (ng/ml) = 0.85 DSL (ng/ml) -0.32 ng/ml, r = 0.952). Most infants (93%) had age- and gender-adjusted NE-17OHP and E-17OHP levels within the recalculated RI. Serum 17OHP significantly increased throughout prepuberty (p < 0.001). Sexual dimorphism was only observed at T IV-V.

When evaluating 17OHP during childhood, we recommend taking into account the extraction procedure in neonates, the method used, age, and the Tanner's stage.