Congenital adrenal hyperplasia: neonatal mass screening compared with clinical diagnosis only in the Emilia-Romagna region of Italy, 1980-1995.

OBJECTIVE: Comparative study of the incidence of classic 21-hydroxylase deficiency congenital adrenal hyperplasia (21ase-def CAH) and clinical findings of affected infants diagnosed via newborn screening versus case survey only in the Emilia-Romagna region of Italy.
METHODS: Neonatal mass screening (from March 1980 to September 1983-Period A, and from March 1991 to August 1995-Period C) and case survey study (from 1980 to June 1995; case survey alone from October 1983 to February 1991--Period B) were performed by the Regional Referral Center for Neonatal Screening for Endocrine-Metabolic Disease with a laboratory (Central Laboratory, S. Orsola Hospital, Bologna) and clinical (First Pediatric Clinic, University of Bologna, S. Orsola Hospital, Bologna) component. A population-based sample of 420 960 newborns consecutively born in the Emilia-Romagna region from March 1980 to August 1995 were studied. Spot 17-OH-progesterone (nmol/L blood) was tested by the radioimmunoassay method after sample extraction during Period A and by fluoroimmunometric time resolved method without sample extraction during Period C. Serum 17-OH-progesterone (ng/dL or nmol/L) was tested by the radioimmunoassay method (Diagnostic Product Corporation Kit, Los Angeles, CA). The case survey was performed by means of a questionnaire sent to all regional centers dealing with pediatrics, neonatology, endocrinology, and pediatric surgery.
RESULTS: Thirteen classic 21ase-def CAH were diagnosed by means of neonatal screening (combined A and C periods). One true and one questionable false-negative cases were identified. The incidence of classical 21-hydroxylase deficiency for the white population was 1:15 518 (95% confidence limits 1:9249-1:28 400) by neonatal screening plus case survey, 1:18 105 (95% confidence limits 1:10 365-1:35 041) by neonatal screening alone and 1:25 462 (95% confidence limits 1:12 925-1:59 043) by case survey alone. The sensitivity and specificity of screening for classic CAH were 83% and 99.8% for Period A and 90% and 99.2% for Period C, respectively. The percentage of salt-wasting forms and the male/female ratio were higher during the neonatal screening period than during the case survey only. Sixty-one percent of classic CAH patients benefited from a prompt diagnosis. Nonclassical 21ase-def CAH cases detected via screening and case survey were also reported.
CONCLUSIONS: Even in a region with adequate neonatal services, clinical diagnosis alone of classic CAH might be delayed or misinterpreted and salt-wasting crises could cause neonatal deaths. CAH screening is thus an effective tool for diagnosing affected male infants without a family history of CAH and for preventing salt loss. However, to achieve maximal benefit from screening, quick procedures are necessary for notification of positive results and beginning prompt treatment. The possibility of false-negative cases indicates that clinical observation should never be abandoned, even with ongoing screening programs.