Clinical and laboratory follow-up of cases referred by the 17-OHP elevation in newborn screening test at Akdeniz University pediatric endocrinology policy clinic

Congenital adrenal hyperplasia (CAH) is an autosomal recessive endocrine disorder caused by enzyme defects in the adrenal steroidogenic pathway. In infants with classic CAH, severe deficiency of adrenal cortisol and aldosterone can precipitate life-threatening salt-wasting crises within the first weeks of life. To prevent such crises, many countries screen neonates early by measuring 17-hydroxyprogesterone (17-OHP) in heel-prick blood samples. In preterm and low birth-weight neonates, physiologically elevated 17-OHP levels reduce test specificity and lead to false-positive results. Therefore, successful newborn screening programs must optimize both sensitivity (to avert adrenal crises) and specificity (to avoid unnecessary interventions). To evaluate the clinical and laboratory follow-up outcomes of infants referred to a pediatric endocrinology clinic for elevated 17-OHP on newborn screening. Specifically, we examined the positive predictive value (PPV) of screening, causes of false positivity, clinical course, and the impact of prematurity and low birth weight on screening performance. Between 2022 and 2025, we retrospectively assessed 118 infants referred to Akdeniz University Hospital for positive CAH screening. Serum 17-OHP assays were performed using a chemiluminescent immunoassay (CLIA). When indicated, an ACTH (cosyntropin) stimulation test was undertaken. Demographic characteristics, hormonal measurements, and follow-up findings were recorded. Statistical analyses employed χ² tests, Student's t test/Mann–Whitney U test, and ANOVA/Kruskal–Wallis tests, with p<0,05 considered statistically significant. Of the cohort, 35.6% were female (n=42) and 64.4% male. A diagnosis of CAH was established in 7 infants (5.9%); 65 infants (55.1%) were classified as false positives, and evaluations were ongoing in 46 (39,0%). Among those with CAH, 42.8% were female and 57.2% male. The mean age at presentation was approximately 30 days (range, 8–196 days). Overall, 84.7% were preterm (gestational age ≤36 weeks) and 59.3% had low birth weight (<2500 g). Screening 17-OHP concentrations were significantly higher in infants <2500 g compared with those ≥2500 g (mean 11.7 vs 7.0 ng/mL; p=0,004). In contrast, baseline serum 17-OHP at the first outpatient visit was higher in term than in preterm infants (mean 14.2 vs 11.3 ng/mL; p<0,001). No correlation was observed between screening and serum 17-OHP values (r≈0.11, p>0.2). Consanguinity was present in 28.6% of infants with CAH versus 3.1% of screen-positive infants in whom CAH was excluded (p<0,001). A family history of CAH was identified in 4 infants (3.4%). At presentation, 98.3% were asymptomatic; only one infant had vomiting and one had feeding difficulty. Among the seven infants who underwent ACTH stimulation testing, five (71.4%) had positive results. The mean follow-up duration was 9.1 months (range, 3–27 months). In false-positive cases, serial control measurements showed a decline of serum 17-OHP to approximately 5 ng/mL by the third assessment. Appropriate therapy was initiated in all seven infants with classic CAH, preventing adrenal crises; no serious complications were observed during follow-up. In our study, prematurity, low birth weight, and secondary stressors were clearly shown to increase 17-hydroxyprogesterone (17-OHP) levels and to result in false-positive findings. Our study delineates the analytical limitations of current assay methods and the consequent problem of false positivity. To enhance the specificity of screening programs, in addition to confirmatory serum testing, integrating second-tier LC-MS/MS or 21-deoxycortisol measurements into pediatric endocrinology outpatient diagnostic pathways is of paramount importance. Key Words: congenital adrenal hyperplasia, 21-hydroxylase deficiency, newborn screening, prematurity, low birth weight, positive predictive value